diff --git a/Cargo.toml b/Cargo.toml
index af01891..71d2a04 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -26,6 +26,7 @@ serde = { version = "1", features = ["derive"], optional = true }
 tokio = ["dep:tokio"]
 bytes = ["dep:bytes"]
 serde = ["dep:serde", "bytes/serde"]
+fault-tolerant = []
 
 [dev-dependencies]
 anyhow = "1"
diff --git a/README.md b/README.md
index 3c1f636..4d71313 100644
--- a/README.md
+++ b/README.md
@@ -17,6 +17,20 @@ Using this library does require some additional knowledge of the format otherwis
 
 See the [documentation](https://docs.rs/mp4-atom).
 
+## Fault-Tolerant Parsing
+Enable the `fault-tolerant` feature to support parsing files with unexpected boxes.
+
+```toml
+[dependencies]
+mp4-atom = { version = "<VERSION>", features = ["fault-tolerant"] }
+```
+
+When this feature is enabled, if a container box (such as `moov`, `trak`, `mdia`, etc.) encounters an unexpected child box during decoding, instead of returning an error, the unknown box is collected in an `unexpected: Vec<Any>` field.
+
+When the feature is **disabled** (default), encountering an unexpected box will return an `Error::UnexpectedBox` error, ensuring strict compliance with the expected structure.
+
+Note that when encoding, the `unexpected` boxes are **not** written back - only the explicitly defined fields are encoded.
+
 ## Examples
 ### Decoding/encoding a byte buffer
 ```rust
diff --git a/src/atom.rs b/src/atom.rs
index 01fb508..9cc8524 100644
--- a/src/atom.rs
+++ b/src/atom.rs
@@ -175,6 +175,9 @@ macro_rules! nested {
                 $( let mut [<$optional:lower>] = None;)*
                 $( let mut [<$multiple:lower>] = Vec::new();)*
 
+                #[cfg(feature = "fault-tolerant")]
+                let mut unexpected = Vec::new();
+
                 while let Some(atom) = Any::decode_maybe(buf)? {
                     match atom {
                         $(Any::$required(atom) => {
@@ -195,7 +198,17 @@ macro_rules! nested {
                         Any::Unknown(kind, _) => {
                             tracing::warn!("unknown box: {:?}", kind);
                         },
-                        _ => return Err(Error::UnexpectedBox(atom.kind())),
+                        _ => {
+                            #[cfg(feature = "fault-tolerant")]
+                            {
+                                tracing::warn!("unexpected box: {:?}", atom.kind());
+                                unexpected.push(atom);
+                            }
+                            #[cfg(not(feature = "fault-tolerant"))]
+                            {
+                                return Err(Error::UnexpectedBox(atom.kind()));
+                            }
+                        }
                     }
                 }
 
@@ -203,6 +216,8 @@ macro_rules! nested {
                     $([<$required:lower>]: [<$required:lower>].ok_or(Error::MissingBox($required::KIND))? ,)*
                     $([<$optional:lower>],)*
                     $([<$multiple:lower>],)*
+                    #[cfg(feature = "fault-tolerant")]
+                    unexpected
                 })
             }
 
diff --git a/src/lib.rs b/src/lib.rs
index 4b403ca..0a6f3e5 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -16,6 +16,19 @@
 //! The simplest way to decode with this library is with [Any::decode], returning any supported atom in a giant enum.
 //! For encoding you will call encode on the atom directly, ex: [Moov::encode].
 //!
+//! Enable the `fault-tolerant` feature to support parsing files with unexpected boxes.
+//!
+//! ```toml
+//! [dependencies]
+//! mp4-atom = { version = "<VERSION>", features = ["fault-tolerant"] }
+//! ```
+//!
+//! When this feature is enabled, if a container box (such as `moov`, `trak`, `mdia`, etc.) encounters an unexpected child box during decoding, instead of returning an error, the unknown box is collected in an `unexpected: Vec<Any>` field.
+//!
+//! When the feature is **disabled** (default), encountering an unexpected box will return an `Error::UnexpectedBox` error, ensuring strict compliance with the expected structure.
+//!
+//! Note that when encoding, the `unexpected` boxes are **not** written back - only the explicitly defined fields are encoded.
+//!
 //! ## Traits
 //! This library gates functionality behind quite a few traits:
 //!
diff --git a/src/meta/iprp.rs b/src/meta/iprp.rs
index 160338c..0650f66 100644
--- a/src/meta/iprp.rs
+++ b/src/meta/iprp.rs
@@ -8,6 +8,8 @@ use crate::*;
 pub struct Iprp {
     pub ipco: Ipco,
     pub ipma: Vec<Ipma>,
+    #[cfg(feature = "fault-tolerant")]
+    pub unexpected: Vec<Any>,
 }
 
 impl Atom for Iprp {
diff --git a/src/meta/mod.rs b/src/meta/mod.rs
index ede274a..b10fc6d 100644
--- a/src/meta/mod.rs
+++ b/src/meta/mod.rs
@@ -158,6 +158,8 @@ mod tests {
                     location: "".into(),
                 }],
             },
+            #[cfg(feature = "fault-tolerant")]
+            unexpected: vec![],
         });
         expected.push(Iloc {
             item_locations: vec![ItemLocation {
@@ -229,6 +231,8 @@ mod tests {
                     },
                 ],
             }],
+            #[cfg(feature = "fault-tolerant")]
+            unexpected: vec![],
         });
         expected.push(Iref {
             references: vec![Reference {
diff --git a/src/moof/mod.rs b/src/moof/mod.rs
index 3e127a6..84ba924 100644
--- a/src/moof/mod.rs
+++ b/src/moof/mod.rs
@@ -6,11 +6,13 @@ pub use traf::*;
 
 use crate::*;
 
-#[derive(Debug, Clone, PartialEq, Eq, Default)]
+#[derive(Debug, Clone, PartialEq, Default)]
 #[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
 pub struct Moof {
     pub mfhd: Mfhd,
     pub traf: Vec<Traf>,
+    #[cfg(feature = "fault-tolerant")]
+    pub unexpected: Vec<Any>,
 }
 
 impl Atom for Moof {
diff --git a/src/moof/traf/mod.rs b/src/moof/traf/mod.rs
index 8c520b8..2304102 100644
--- a/src/moof/traf/mod.rs
+++ b/src/moof/traf/mod.rs
@@ -8,7 +8,7 @@ pub use trun::*;
 
 use crate::*;
 
-#[derive(Debug, Clone, PartialEq, Eq, Default)]
+#[derive(Debug, Clone, PartialEq, Default)]
 #[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
 pub struct Traf {
     pub tfhd: Tfhd,
@@ -21,6 +21,8 @@ pub struct Traf {
     pub saio: Vec<Saio>,
     pub meta: Option<Meta>,
     pub udta: Option<Udta>,
+    #[cfg(feature = "fault-tolerant")]
+    pub unexpected: Vec<Any>,
 }
 
 impl Atom for Traf {
diff --git a/src/moov/mod.rs b/src/moov/mod.rs
index 0e43a5a..5f0021a 100644
--- a/src/moov/mod.rs
+++ b/src/moov/mod.rs
@@ -18,6 +18,8 @@ pub struct Moov {
     pub mvex: Option<Mvex>,
     pub trak: Vec<Trak>,
     pub udta: Option<Udta>,
+    #[cfg(feature = "fault-tolerant")]
+    pub unexpected: Vec<Any>,
 }
 
 impl Atom for Moov {
@@ -137,7 +139,9 @@ mod test {
                         default_sample_description_index: 1,
                         default_sample_duration: 3000,
                         ..Default::default()
-                    }]
+                    }],
+                    #[cfg(feature = "fault-tolerant")]
+                    unexpected: vec![],
                 }),
                 trak: vec![Trak {
                     tkhd: Tkhd {
@@ -156,7 +160,9 @@ mod test {
                                 media_rate: 1,
                                 ..Default::default()
                             }]
-                        })
+                        }),
+                        #[cfg(feature = "fault-tolerant")]
+                        unexpected: vec![],
                     }),
                     meta: None,
                     mdia: Mdia {
@@ -184,7 +190,9 @@ mod test {
                             dinf: Dinf {
                                 dref: Dref {
                                     urls: vec![Url::default()]
-                                }
+                                },
+                                #[cfg(feature = "fault-tolerant")]
+                                unexpected: vec![],
                             },
                             stbl: Stbl {
                                 stsd: Stsd {
@@ -219,17 +227,27 @@ mod test {
                                         colr: None,
                                         pasp: None,
                                         taic: None,
+                                        #[cfg(feature = "fault-tolerant")]
+                                        unexpected: vec![],
                                     }
                                     .into()],
                                 },
                                 stco: Some(Stco::default()),
                                 ..Default::default()
-                            }
-                        }
+                            },
+                            #[cfg(feature = "fault-tolerant")]
+                            unexpected: vec![],
+                        },
+                        #[cfg(feature = "fault-tolerant")]
+                        unexpected: vec![],
                     },
-                    udta: None
+                    udta: None,
+                    #[cfg(feature = "fault-tolerant")]
+                    unexpected: vec![],
                 }],
                 udta: None,
+                #[cfg(feature = "fault-tolerant")]
+                unexpected: vec![],
             }
         )
     }
diff --git a/src/moov/mvex/mod.rs b/src/moov/mvex/mod.rs
index 1ae169c..43031c9 100644
--- a/src/moov/mvex/mod.rs
+++ b/src/moov/mvex/mod.rs
@@ -6,11 +6,13 @@ pub use trex::*;
 
 use crate::*;
 
-#[derive(Debug, Clone, PartialEq, Eq, Default)]
+#[derive(Debug, Clone, PartialEq, Default)]
 #[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
 pub struct Mvex {
     pub mehd: Option<Mehd>,
     pub trex: Vec<Trex>,
+    #[cfg(feature = "fault-tolerant")]
+    pub unexpected: Vec<Any>,
 }
 
 impl Atom for Mvex {
diff --git a/src/moov/trak/edts/mod.rs b/src/moov/trak/edts/mod.rs
index ebf5c2f..c0966c2 100644
--- a/src/moov/trak/edts/mod.rs
+++ b/src/moov/trak/edts/mod.rs
@@ -3,10 +3,12 @@ pub use elst::*;
 
 use crate::*;
 
-#[derive(Debug, Clone, PartialEq, Eq, Default)]
+#[derive(Debug, Clone, PartialEq, Default)]
 #[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
 pub struct Edts {
     pub elst: Option<Elst>,
+    #[cfg(feature = "fault-tolerant")]
+    pub unexpected: Vec<Any>,
 }
 
 impl Atom for Edts {
diff --git a/src/moov/trak/mdia/minf/dinf/mod.rs b/src/moov/trak/mdia/minf/dinf/mod.rs
index 5e65768..7b77ea2 100644
--- a/src/moov/trak/mdia/minf/dinf/mod.rs
+++ b/src/moov/trak/mdia/minf/dinf/mod.rs
@@ -3,10 +3,12 @@ pub use dref::*;
 
 use crate::*;
 
-#[derive(Debug, Clone, PartialEq, Eq, Default)]
+#[derive(Debug, Clone, PartialEq, Default)]
 #[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
 pub struct Dinf {
     pub dref: Dref,
+    #[cfg(feature = "fault-tolerant")]
+    pub unexpected: Vec<Any>,
 }
 
 impl Atom for Dinf {
diff --git a/src/moov/trak/mdia/minf/mod.rs b/src/moov/trak/mdia/minf/mod.rs
index c57ef11..a85d433 100644
--- a/src/moov/trak/mdia/minf/mod.rs
+++ b/src/moov/trak/mdia/minf/mod.rs
@@ -10,13 +10,15 @@ pub use vmhd::*;
 
 use crate::*;
 
-#[derive(Debug, Clone, PartialEq, Eq, Default)]
+#[derive(Debug, Clone, PartialEq, Default)]
 #[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
 pub struct Minf {
     pub vmhd: Option<Vmhd>,
     pub smhd: Option<Smhd>,
     pub dinf: Dinf,
     pub stbl: Stbl,
+    #[cfg(feature = "fault-tolerant")]
+    pub unexpected: Vec<Any>,
 }
 
 impl Atom for Minf {
diff --git a/src/moov/trak/mdia/minf/stbl/mod.rs b/src/moov/trak/mdia/minf/stbl/mod.rs
index 0f9ab03..01fc384 100644
--- a/src/moov/trak/mdia/minf/stbl/mod.rs
+++ b/src/moov/trak/mdia/minf/stbl/mod.rs
@@ -26,7 +26,7 @@ pub use subs::*;
 
 use crate::*;
 
-#[derive(Debug, Clone, PartialEq, Eq, Default)]
+#[derive(Debug, Clone, PartialEq, Default)]
 #[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
 pub struct Stbl {
     pub stsd: Stsd,
@@ -42,6 +42,8 @@ pub struct Stbl {
     pub subs: Vec<Subs>,
     pub saiz: Vec<Saiz>,
     pub saio: Vec<Saio>,
+    #[cfg(feature = "fault-tolerant")]
+    pub unexpected: Vec<Any>,
 }
 
 impl Atom for Stbl {
diff --git a/src/moov/trak/mdia/minf/stbl/stsd/ac3.rs b/src/moov/trak/mdia/minf/stbl/stsd/ac3.rs
index e764864..83f29b8 100644
--- a/src/moov/trak/mdia/minf/stbl/stsd/ac3.rs
+++ b/src/moov/trak/mdia/minf/stbl/stsd/ac3.rs
@@ -2,11 +2,13 @@ use crate::*;
 
 // See ETSI TS 102 366 V1.4.1 (2017-09) for details of AC-3 and EAC-3
 
-#[derive(Debug, Clone, PartialEq, Eq)]
+#[derive(Debug, Clone, PartialEq)]
 #[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
 pub struct Ac3 {
     pub audio: Audio,
     pub dac3: Ac3SpecificBox,
+    #[cfg(feature = "fault-tolerant")]
+    pub unexpected: Vec<Any>,
 }
 
 impl Atom for Ac3 {
@@ -16,17 +18,28 @@ impl Atom for Ac3 {
         let audio = Audio::decode(buf)?;
 
         let mut dac3 = None;
+        #[cfg(feature = "fault-tolerant")]
+        let mut unexpected = Vec::new();
 
         while let Some(atom) = Any::decode_maybe(buf)? {
             match atom {
                 Any::Ac3SpecificBox(atom) => dac3 = atom.into(),
-                _ => tracing::warn!("unknown atom: {:?}", atom),
+                _ => {
+                    tracing::warn!("unknown atom: {:?}", atom);
+                    #[cfg(feature = "fault-tolerant")]
+                    unexpected.push(atom);
+
+                    #[cfg(not(feature = "fault-tolerant"))]
+                    return Err(Error::UnexpectedBox(atom.kind()));
+                }
             }
         }
 
         Ok(Self {
             audio,
             dac3: dac3.ok_or(Error::MissingBox(Ac3SpecificBox::KIND))?,
+            #[cfg(feature = "fault-tolerant")]
+            unexpected,
         })
     }
 
@@ -120,7 +133,9 @@ mod tests {
                     acmod: 2,
                     lfeon: false,
                     bit_rate_code: 10
-                }
+                },
+                #[cfg(feature = "fault-tolerant")]
+                unexpected: vec![],
             }
         );
     }
@@ -142,6 +157,8 @@ mod tests {
                 lfeon: false,
                 bit_rate_code: 10,
             },
+            #[cfg(feature = "fault-tolerant")]
+            unexpected: vec![],
         };
 
         let mut buf = Vec::new();
diff --git a/src/moov/trak/mdia/minf/stbl/stsd/av01.rs b/src/moov/trak/mdia/minf/stbl/stsd/av01.rs
index efc30d2..741bef8 100644
--- a/src/moov/trak/mdia/minf/stbl/stsd/av01.rs
+++ b/src/moov/trak/mdia/minf/stbl/stsd/av01.rs
@@ -3,7 +3,7 @@ use crate::{Any, Atom, Buf, BufMut, DecodeMaybe, Error, FourCC, Result};
 
 use super::{Btrt, Colr, Pasp, Taic, Visual};
 
-#[derive(Debug, Clone, PartialEq, Eq, Default)]
+#[derive(Debug, Clone, PartialEq, Default)]
 #[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
 pub struct Av01 {
     pub visual: Visual,
@@ -12,6 +12,8 @@ pub struct Av01 {
     pub colr: Option<Colr>,
     pub pasp: Option<Pasp>,
     pub taic: Option<Taic>,
+    #[cfg(feature = "fault-tolerant")]
+    pub unexpected: Vec<Any>,
 }
 
 impl Atom for Av01 {
@@ -25,6 +27,9 @@ impl Atom for Av01 {
         let mut colr = None;
         let mut pasp = None;
         let mut taic = None;
+        #[cfg(feature = "fault-tolerant")]
+        let mut unexpected = Vec::new();
+
         while let Some(atom) = Any::decode_maybe(buf)? {
             match atom {
                 Any::Av1c(atom) => av1c = atom.into(),
@@ -32,7 +37,14 @@ impl Atom for Av01 {
                 Any::Colr(atom) => colr = atom.into(),
                 Any::Pasp(atom) => pasp = atom.into(),
                 Any::Taic(atom) => taic = atom.into(),
-                _ => tracing::warn!("unknown atom: {:?}", atom),
+                _ => {
+                    tracing::warn!("unknown atom: {:?}", atom);
+                    #[cfg(feature = "fault-tolerant")]
+                    unexpected.push(atom);
+
+                    #[cfg(not(feature = "fault-tolerant"))]
+                    return Err(Error::UnexpectedBox(atom.kind()));
+                }
             }
         }
 
@@ -43,6 +55,8 @@ impl Atom for Av01 {
             colr,
             pasp,
             taic,
+            #[cfg(feature = "fault-tolerant")]
+            unexpected,
         })
     }
 
diff --git a/src/moov/trak/mdia/minf/stbl/stsd/eac3.rs b/src/moov/trak/mdia/minf/stbl/stsd/eac3.rs
index a2316f6..e629d8d 100644
--- a/src/moov/trak/mdia/minf/stbl/stsd/eac3.rs
+++ b/src/moov/trak/mdia/minf/stbl/stsd/eac3.rs
@@ -2,11 +2,13 @@ use crate::*;
 
 // See ETSI TS 102 366 V1.4.1 (2017-09) for details of AC-3 and EAC-3
 
-#[derive(Debug, Clone, PartialEq, Eq)]
+#[derive(Debug, Clone, PartialEq)]
 #[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
 pub struct Eac3 {
     pub audio: Audio,
     pub dec3: Ec3SpecificBox,
+    #[cfg(feature = "fault-tolerant")]
+    pub unexpected: Vec<Any>,
 }
 
 impl Atom for Eac3 {
@@ -16,17 +18,28 @@ impl Atom for Eac3 {
         let audio = Audio::decode(buf)?;
 
         let mut dec3 = None;
+        #[cfg(feature = "fault-tolerant")]
+        let mut unexpected = Vec::new();
 
         while let Some(atom) = Any::decode_maybe(buf)? {
             match atom {
                 Any::Ec3SpecificBox(atom) => dec3 = atom.into(),
-                _ => tracing::warn!("unknown atom: {:?}", atom),
+                _ => {
+                    tracing::warn!("unknown atom: {:?}", atom);
+                    #[cfg(feature = "fault-tolerant")]
+                    unexpected.push(atom);
+
+                    #[cfg(not(feature = "fault-tolerant"))]
+                    return Err(Error::UnexpectedBox(atom.kind()));
+                }
             }
         }
 
         Ok(Self {
             audio,
             dec3: dec3.ok_or(Error::MissingBox(Ec3SpecificBox::KIND))?,
+            #[cfg(feature = "fault-tolerant")]
+            unexpected,
         })
     }
 
@@ -180,7 +193,9 @@ mod tests {
                         num_dep_sub: 0,
                         chan_loc: None
                     }]
-                }
+                },
+                #[cfg(feature = "fault-tolerant")]
+                unexpected: vec![],
             }
         );
     }
@@ -207,6 +222,8 @@ mod tests {
                     chan_loc: None,
                 }],
             },
+            #[cfg(feature = "fault-tolerant")]
+            unexpected: vec![],
         };
 
         let mut buf = Vec::new();
@@ -238,6 +255,8 @@ mod tests {
                     chan_loc: Some(0x1FF),
                 }],
             },
+            #[cfg(feature = "fault-tolerant")]
+            unexpected: vec![],
         };
 
         // Encode
@@ -287,6 +306,8 @@ mod tests {
                     },
                 ],
             },
+            #[cfg(feature = "fault-tolerant")]
+            unexpected: vec![],
         };
 
         // Encode
@@ -342,7 +363,9 @@ mod tests {
                         num_dep_sub: 0,
                         chan_loc: None
                     }]
-                }
+                },
+                #[cfg(feature = "fault-tolerant")]
+                unexpected: vec![],
             }
         );
     }
diff --git a/src/moov/trak/mdia/minf/stbl/stsd/flac.rs b/src/moov/trak/mdia/minf/stbl/stsd/flac.rs
index 082a40a..52d95d0 100644
--- a/src/moov/trak/mdia/minf/stbl/stsd/flac.rs
+++ b/src/moov/trak/mdia/minf/stbl/stsd/flac.rs
@@ -1,10 +1,12 @@
 use crate::*;
 
-#[derive(Debug, Clone, PartialEq, Eq)]
+#[derive(Debug, Clone, PartialEq)]
 #[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
 pub struct Flac {
     pub audio: Audio,
     pub dfla: Dfla,
+    #[cfg(feature = "fault-tolerant")]
+    pub unexpected: Vec<Any>,
 }
 
 impl Atom for Flac {
@@ -14,16 +16,28 @@ impl Atom for Flac {
         let audio = Audio::decode(buf)?;
 
         let mut dfla = None;
+        #[cfg(feature = "fault-tolerant")]
+        let mut unexpected = Vec::new();
+
         while let Some(atom) = Any::decode_maybe(buf)? {
             match atom {
                 Any::Dfla(atom) => dfla = atom.into(),
-                _ => tracing::warn!("unknown atom: {:?}", atom),
+                _ => {
+                    tracing::warn!("unknown atom: {:?}", atom);
+                    #[cfg(feature = "fault-tolerant")]
+                    unexpected.push(atom);
+
+                    #[cfg(not(feature = "fault-tolerant"))]
+                    return Err(Error::UnexpectedBox(atom.kind()));
+                }
             }
         }
 
         Ok(Self {
             audio,
             dfla: dfla.ok_or(Error::MissingBox(Dfla::KIND))?,
+            #[cfg(feature = "fault-tolerant")]
+            unexpected,
         })
     }
 
diff --git a/src/moov/trak/mdia/minf/stbl/stsd/h264/avc1.rs b/src/moov/trak/mdia/minf/stbl/stsd/h264/avc1.rs
index ad0417e..c4732b1 100644
--- a/src/moov/trak/mdia/minf/stbl/stsd/h264/avc1.rs
+++ b/src/moov/trak/mdia/minf/stbl/stsd/h264/avc1.rs
@@ -1,6 +1,6 @@
 use crate::*;
 
-#[derive(Debug, Clone, PartialEq, Eq, Default)]
+#[derive(Debug, Clone, PartialEq, Default)]
 #[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
 pub struct Avc1 {
     pub visual: Visual,
@@ -9,6 +9,9 @@ pub struct Avc1 {
     pub colr: Option<Colr>,
     pub pasp: Option<Pasp>,
     pub taic: Option<Taic>,
+
+    #[cfg(feature = "fault-tolerant")]
+    pub unexpected: Vec<Any>,
 }
 
 impl Atom for Avc1 {
@@ -22,6 +25,10 @@ impl Atom for Avc1 {
         let mut colr = None;
         let mut pasp = None;
         let mut taic = None;
+
+        #[cfg(feature = "fault-tolerant")]
+        let mut unexpected = Vec::new();
+
         while let Some(atom) = Any::decode_maybe(buf)? {
             match atom {
                 Any::Avcc(atom) => avcc = atom.into(),
@@ -29,7 +36,14 @@ impl Atom for Avc1 {
                 Any::Colr(atom) => colr = atom.into(),
                 Any::Pasp(atom) => pasp = atom.into(),
                 Any::Taic(atom) => taic = atom.into(),
-                _ => tracing::warn!("unknown atom: {:?}", atom),
+                _ => {
+                    tracing::warn!("unknown atom: {:?}", atom);
+                    #[cfg(feature = "fault-tolerant")]
+                    unexpected.push(atom);
+
+                    #[cfg(not(feature = "fault-tolerant"))]
+                    return Err(Error::UnexpectedBox(atom.kind()));
+                }
             }
         }
 
@@ -40,6 +54,8 @@ impl Atom for Avc1 {
             colr,
             pasp,
             taic,
+            #[cfg(feature = "fault-tolerant")]
+            unexpected,
         })
     }
 
@@ -96,6 +112,8 @@ mod tests {
             colr: None,
             pasp: None,
             taic: None,
+            #[cfg(feature = "fault-tolerant")]
+            unexpected: Vec::new(),
         };
         let mut buf = Vec::new();
         expected.encode(&mut buf).unwrap();
@@ -147,6 +165,8 @@ mod tests {
                 clock_drift_rate: i32::MAX,
                 clock_type: ClockType::CanSync,
             }),
+            #[cfg(feature = "fault-tolerant")]
+            unexpected: Vec::new(),
         };
         let mut buf = Vec::new();
         expected.encode(&mut buf).unwrap();
diff --git a/src/moov/trak/mdia/minf/stbl/stsd/hevc/hev1.rs b/src/moov/trak/mdia/minf/stbl/stsd/hevc/hev1.rs
index bd726de..b7d021c 100644
--- a/src/moov/trak/mdia/minf/stbl/stsd/hevc/hev1.rs
+++ b/src/moov/trak/mdia/minf/stbl/stsd/hevc/hev1.rs
@@ -1,6 +1,6 @@
 use crate::*;
 
-#[derive(Debug, Clone, PartialEq, Eq, Default)]
+#[derive(Debug, Clone, PartialEq, Default)]
 #[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
 pub struct Hev1 {
     pub visual: Visual,
@@ -9,6 +9,9 @@ pub struct Hev1 {
     pub colr: Option<Colr>,
     pub pasp: Option<Pasp>,
     pub taic: Option<Taic>,
+
+    #[cfg(feature = "fault-tolerant")]
+    pub unexpected: Vec<Any>,
 }
 
 impl Atom for Hev1 {
@@ -22,6 +25,10 @@ impl Atom for Hev1 {
         let mut colr = None;
         let mut pasp = None;
         let mut taic = None;
+
+        #[cfg(feature = "fault-tolerant")]
+        let mut unexpected = Vec::new();
+
         while let Some(atom) = Any::decode_maybe(buf)? {
             match atom {
                 Any::Hvcc(atom) => hvcc = atom.into(),
@@ -29,7 +36,14 @@ impl Atom for Hev1 {
                 Any::Colr(atom) => colr = atom.into(),
                 Any::Pasp(atom) => pasp = atom.into(),
                 Any::Taic(atom) => taic = atom.into(),
-                _ => tracing::warn!("unknown atom: {:?}", atom),
+                _ => {
+                    tracing::warn!("unknown atom: {:?}", atom);
+                    #[cfg(feature = "fault-tolerant")]
+                    unexpected.push(atom);
+
+                    #[cfg(not(feature = "fault-tolerant"))]
+                    return Err(Error::UnexpectedBox(atom.kind()));
+                }
             }
         }
 
@@ -40,6 +54,8 @@ impl Atom for Hev1 {
             colr,
             pasp,
             taic,
+            #[cfg(feature = "fault-tolerant")]
+            unexpected,
         })
     }
 
@@ -84,10 +100,7 @@ mod tests {
                 configuration_version: 1,
                 ..Default::default()
             },
-            btrt: None,
-            colr: None,
-            pasp: None,
-            taic: None,
+            ..Default::default()
         };
         let mut buf = Vec::new();
         expected.encode(&mut buf).unwrap();
diff --git a/src/moov/trak/mdia/minf/stbl/stsd/hevc/hvc1.rs b/src/moov/trak/mdia/minf/stbl/stsd/hevc/hvc1.rs
index 6c7b2c9..a93fba4 100644
--- a/src/moov/trak/mdia/minf/stbl/stsd/hevc/hvc1.rs
+++ b/src/moov/trak/mdia/minf/stbl/stsd/hevc/hvc1.rs
@@ -1,6 +1,6 @@
 use crate::*;
 
-#[derive(Debug, Clone, PartialEq, Eq, Default)]
+#[derive(Debug, Clone, PartialEq, Default)]
 #[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
 pub struct Hvc1 {
     pub visual: Visual,
@@ -10,6 +10,9 @@ pub struct Hvc1 {
     pub colr: Option<Colr>,
     pub pasp: Option<Pasp>,
     pub taic: Option<Taic>,
+
+    #[cfg(feature = "fault-tolerant")]
+    pub unexpected: Vec<Any>,
 }
 
 impl Atom for Hvc1 {
@@ -23,6 +26,10 @@ impl Atom for Hvc1 {
         let mut colr = None;
         let mut pasp = None;
         let mut taic = None;
+
+        #[cfg(feature = "fault-tolerant")]
+        let mut unexpected = Vec::new();
+
         while let Some(atom) = Any::decode_maybe(buf)? {
             match atom {
                 Any::Hvcc(atom) => hvcc = atom.into(),
@@ -30,7 +37,13 @@ impl Atom for Hvc1 {
                 Any::Colr(atom) => colr = atom.into(),
                 Any::Pasp(atom) => pasp = atom.into(),
                 Any::Taic(atom) => taic = atom.into(),
-                _ => tracing::warn!("unknown atom: {:?}", atom),
+                _ => {
+                    tracing::warn!("unknown atom: {:?}", atom);
+                    #[cfg(feature = "fault-tolerant")]
+                    unexpected.push(atom);
+                    #[cfg(not(feature = "fault-tolerant"))]
+                    return Err(Error::UnexpectedBox(atom.kind()));
+                }
             }
         }
 
@@ -41,6 +54,9 @@ impl Atom for Hvc1 {
             colr,
             pasp,
             taic,
+
+            #[cfg(feature = "fault-tolerant")]
+            unexpected,
         })
     }
 
diff --git a/src/moov/trak/mdia/minf/stbl/stsd/hevc/hvcc.rs b/src/moov/trak/mdia/minf/stbl/stsd/hevc/hvcc.rs
index 9fb8f9d..e45eb70 100644
--- a/src/moov/trak/mdia/minf/stbl/stsd/hevc/hvcc.rs
+++ b/src/moov/trak/mdia/minf/stbl/stsd/hevc/hvcc.rs
@@ -169,10 +169,7 @@ mod tests {
                 configuration_version: 1,
                 ..Default::default()
             },
-            btrt: None,
-            colr: None,
-            pasp: None,
-            taic: None,
+            ..Default::default()
         };
         let mut buf = Vec::new();
         expected.encode(&mut buf).unwrap();
diff --git a/src/moov/trak/mdia/minf/stbl/stsd/mod.rs b/src/moov/trak/mdia/minf/stbl/stsd/mod.rs
index afa9d78..46fda96 100644
--- a/src/moov/trak/mdia/minf/stbl/stsd/mod.rs
+++ b/src/moov/trak/mdia/minf/stbl/stsd/mod.rs
@@ -39,14 +39,14 @@ pub use vp9::*;
 use crate::*;
 use derive_more::From;
 
-#[derive(Debug, Clone, PartialEq, Eq, Default)]
+#[derive(Debug, Clone, PartialEq, Default)]
 #[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
 pub struct Stsd {
     pub codecs: Vec<Codec>,
 }
 
 /// Called a "sample entry" in the ISOBMFF specification.
-#[derive(Debug, Clone, PartialEq, Eq, From)]
+#[derive(Debug, Clone, PartialEq, From)]
 #[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
 pub enum Codec {
     // H264
diff --git a/src/moov/trak/mdia/minf/stbl/stsd/mp4a/mod.rs b/src/moov/trak/mdia/minf/stbl/stsd/mp4a/mod.rs
index c06662b..c43d8ae 100644
--- a/src/moov/trak/mdia/minf/stbl/stsd/mp4a/mod.rs
+++ b/src/moov/trak/mdia/minf/stbl/stsd/mp4a/mod.rs
@@ -4,13 +4,15 @@ use crate::*;
 pub mod esds;
 pub use esds::Esds;
 
-#[derive(Debug, Clone, PartialEq, Eq)]
+#[derive(Debug, Clone, PartialEq)]
 #[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
 pub struct Mp4a {
     pub audio: Audio,
     pub esds: Esds,
     pub btrt: Option<Btrt>,
     pub taic: Option<Taic>,
+    #[cfg(feature = "fault-tolerant")]
+    pub unexpected: Vec<Any>,
 }
 
 impl Atom for Mp4a {
@@ -23,13 +25,23 @@ impl Atom for Mp4a {
         let mut esds = None;
         let mut taic = None;
 
+        #[cfg(feature = "fault-tolerant")]
+        let mut unexpected = Vec::new();
+
         // Find esds in mp4a or wave
         while let Some(atom) = Any::decode_maybe(buf)? {
             match atom {
                 Any::Btrt(atom) => btrt = atom.into(),
                 Any::Esds(atom) => esds = atom.into(),
                 Any::Taic(atom) => taic = atom.into(),
-                _ => tracing::warn!("unknown atom: {:?}", atom),
+                _ => {
+                    tracing::warn!("unknown atom: {:?}", atom);
+                    #[cfg(feature = "fault-tolerant")]
+                    unexpected.push(atom);
+
+                    #[cfg(not(feature = "fault-tolerant"))]
+                    return Err(Error::UnexpectedBox(atom.kind()));
+                }
             }
         }
 
@@ -38,6 +50,8 @@ impl Atom for Mp4a {
             esds: esds.ok_or(Error::MissingBox(Esds::KIND))?,
             btrt,
             taic,
+            #[cfg(feature = "fault-tolerant")]
+            unexpected,
         })
     }
 
@@ -90,6 +104,8 @@ mod tests {
                 avg_bitrate: 3,
             }),
             taic: None,
+            #[cfg(feature = "fault-tolerant")]
+            unexpected: vec![],
         };
         let mut buf = Vec::new();
         expected.encode(&mut buf).unwrap();
diff --git a/src/moov/trak/mdia/minf/stbl/stsd/opus.rs b/src/moov/trak/mdia/minf/stbl/stsd/opus.rs
index ad36ec0..d3e5046 100644
--- a/src/moov/trak/mdia/minf/stbl/stsd/opus.rs
+++ b/src/moov/trak/mdia/minf/stbl/stsd/opus.rs
@@ -1,10 +1,12 @@
 use crate::*;
 
-#[derive(Debug, Clone, PartialEq, Eq)]
+#[derive(Debug, Clone, PartialEq)]
 #[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
 pub struct Opus {
     pub audio: Audio,
     pub dops: Dops,
+    #[cfg(feature = "fault-tolerant")]
+    pub unexpected: Vec<Any>,
 }
 
 impl Atom for Opus {
@@ -14,18 +16,29 @@ impl Atom for Opus {
         let audio = Audio::decode(buf)?;
 
         let mut dops = None;
+        #[cfg(feature = "fault-tolerant")]
+        let mut unexpected = Vec::new();
 
         // Find esds in mp4a or wave
         while let Some(atom) = Any::decode_maybe(buf)? {
             match atom {
                 Any::Dops(atom) => dops = atom.into(),
-                _ => tracing::warn!("unknown atom: {:?}", atom),
+                _ => {
+                    tracing::warn!("unknown atom: {:?}", atom);
+                    #[cfg(feature = "fault-tolerant")]
+                    unexpected.push(atom);
+
+                    #[cfg(not(feature = "fault-tolerant"))]
+                    return Err(Error::UnexpectedBox(atom.kind()));
+                }
             }
         }
 
         Ok(Self {
             audio,
             dops: dops.ok_or(Error::MissingBox(Dops::KIND))?,
+            #[cfg(feature = "fault-tolerant")]
+            unexpected,
         })
     }
 
diff --git a/src/moov/trak/mdia/minf/stbl/stsd/uncv.rs b/src/moov/trak/mdia/minf/stbl/stsd/uncv.rs
index 9eca10c..45ea9eb 100644
--- a/src/moov/trak/mdia/minf/stbl/stsd/uncv.rs
+++ b/src/moov/trak/mdia/minf/stbl/stsd/uncv.rs
@@ -2,7 +2,7 @@ use crate::*;
 
 use super::{Btrt, Pasp, Visual};
 
-#[derive(Debug, Clone, PartialEq, Eq)]
+#[derive(Debug, Clone, PartialEq)]
 #[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
 pub struct Uncv {
     pub visual: Visual,
@@ -11,6 +11,8 @@ pub struct Uncv {
     pub btrt: Option<Btrt>,
     pub ccst: Option<Ccst>,
     pub pasp: Option<Pasp>,
+    #[cfg(feature = "fault-tolerant")]
+    pub unexpected: Vec<Any>,
 }
 
 impl Atom for Uncv {
@@ -24,6 +26,9 @@ impl Atom for Uncv {
         let mut uncc = None;
         let mut btrt = None;
         let mut pasp = None;
+        #[cfg(feature = "fault-tolerant")]
+        let mut unexpected = Vec::new();
+
         while let Some(atom) = Any::decode_maybe(buf)? {
             match atom {
                 Any::Cmpd(atom) => cmpd = atom.into(),
@@ -31,7 +36,14 @@ impl Atom for Uncv {
                 Any::Btrt(atom) => btrt = atom.into(),
                 Any::Ccst(atom) => ccst = atom.into(),
                 Any::Pasp(atom) => pasp = atom.into(),
-                _ => tracing::warn!("unknown atom: {:?}", atom),
+                _ => {
+                    tracing::warn!("unknown atom: {:?}", atom);
+                    #[cfg(feature = "fault-tolerant")]
+                    unexpected.push(atom);
+
+                    #[cfg(not(feature = "fault-tolerant"))]
+                    return Err(Error::UnexpectedBox(atom.kind()));
+                }
             }
         }
 
@@ -42,6 +54,8 @@ impl Atom for Uncv {
             btrt,
             ccst,
             pasp,
+            #[cfg(feature = "fault-tolerant")]
+            unexpected,
         })
     }
 
diff --git a/src/moov/trak/mdia/minf/stbl/stsd/vp9/vp08.rs b/src/moov/trak/mdia/minf/stbl/stsd/vp9/vp08.rs
index dea5e65..77a7204 100644
--- a/src/moov/trak/mdia/minf/stbl/stsd/vp9/vp08.rs
+++ b/src/moov/trak/mdia/minf/stbl/stsd/vp9/vp08.rs
@@ -1,11 +1,13 @@
 use crate::*;
 
 // https://www.webmproject.org/vp9/mp4/
-#[derive(Debug, Clone, PartialEq, Eq, Default)]
+#[derive(Debug, Clone, PartialEq, Default)]
 #[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
 pub struct Vp08 {
     pub visual: Visual,
     pub vpcc: VpcC,
+    #[cfg(feature = "fault-tolerant")]
+    pub unexpected: Vec<Any>,
 }
 
 impl Atom for Vp08 {
@@ -15,16 +17,28 @@ impl Atom for Vp08 {
         let visual = Visual::decode(buf)?;
 
         let mut vpcc = None;
+        #[cfg(feature = "fault-tolerant")]
+        let mut unexpected = Vec::new();
+
         while let Some(atom) = Any::decode_maybe(buf)? {
             match atom {
                 Any::VpcC(atom) => vpcc = atom.into(),
-                _ => tracing::warn!("unknown atom: {:?}", atom),
+                _ => {
+                    tracing::warn!("unknown atom: {:?}", atom);
+                    #[cfg(feature = "fault-tolerant")]
+                    unexpected.push(atom);
+
+                    #[cfg(not(feature = "fault-tolerant"))]
+                    return Err(Error::UnexpectedBox(atom.kind()));
+                }
             }
         }
 
         Ok(Self {
             visual,
             vpcc: vpcc.ok_or(Error::MissingBox(VpcC::KIND))?,
+            #[cfg(feature = "fault-tolerant")]
+            unexpected,
         })
     }
 
diff --git a/src/moov/trak/mdia/minf/stbl/stsd/vp9/vp09.rs b/src/moov/trak/mdia/minf/stbl/stsd/vp9/vp09.rs
index 6b7b41f..147bfbf 100644
--- a/src/moov/trak/mdia/minf/stbl/stsd/vp9/vp09.rs
+++ b/src/moov/trak/mdia/minf/stbl/stsd/vp9/vp09.rs
@@ -1,11 +1,13 @@
 use crate::*;
 
 // https://www.webmproject.org/vp9/mp4/
-#[derive(Debug, Clone, PartialEq, Eq, Default)]
+#[derive(Debug, Clone, PartialEq, Default)]
 #[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
 pub struct Vp09 {
     pub visual: Visual,
     pub vpcc: VpcC,
+    #[cfg(feature = "fault-tolerant")]
+    pub unexpected: Vec<Any>,
 }
 
 impl Atom for Vp09 {
@@ -15,16 +17,28 @@ impl Atom for Vp09 {
         let visual = Visual::decode(buf)?;
 
         let mut vpcc = None;
+        #[cfg(feature = "fault-tolerant")]
+        let mut unexpected = Vec::new();
+
         while let Some(atom) = Any::decode_maybe(buf)? {
             match atom {
                 Any::VpcC(atom) => vpcc = atom.into(),
-                _ => tracing::warn!("unknown atom: {:?}", atom),
+                _ => {
+                    tracing::warn!("unknown atom: {:?}", atom);
+                    #[cfg(feature = "fault-tolerant")]
+                    unexpected.push(atom);
+
+                    #[cfg(not(feature = "fault-tolerant"))]
+                    return Err(Error::UnexpectedBox(atom.kind()));
+                }
             }
         }
 
         Ok(Self {
             visual,
             vpcc: vpcc.ok_or(Error::MissingBox(VpcC::KIND))?,
+            #[cfg(feature = "fault-tolerant")]
+            unexpected,
         })
     }
 
@@ -49,6 +63,8 @@ mod tests {
                 ..Default::default()
             },
             vpcc: VpcC::default(),
+            #[cfg(feature = "fault-tolerant")]
+            unexpected: vec![],
         };
         let mut buf = Vec::new();
         expected.encode(&mut buf).unwrap();
diff --git a/src/moov/trak/mdia/mod.rs b/src/moov/trak/mdia/mod.rs
index 4923b39..4594b68 100644
--- a/src/moov/trak/mdia/mod.rs
+++ b/src/moov/trak/mdia/mod.rs
@@ -8,12 +8,14 @@ pub use minf::*;
 
 use crate::*;
 
-#[derive(Debug, Clone, PartialEq, Eq, Default)]
+#[derive(Debug, Clone, PartialEq, Default)]
 #[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
 pub struct Mdia {
     pub mdhd: Mdhd,
     pub hdlr: Hdlr,
     pub minf: Minf,
+    #[cfg(feature = "fault-tolerant")]
+    pub unexpected: Vec<Any>,
 }
 
 impl Atom for Mdia {
diff --git a/src/moov/trak/mod.rs b/src/moov/trak/mod.rs
index 2772f63..a0f6182 100644
--- a/src/moov/trak/mod.rs
+++ b/src/moov/trak/mod.rs
@@ -8,7 +8,7 @@ pub use tkhd::*;
 
 use crate::*;
 
-#[derive(Debug, Clone, PartialEq, Eq, Default)]
+#[derive(Debug, Clone, PartialEq, Default)]
 #[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
 pub struct Trak {
     pub tkhd: Tkhd,
@@ -16,6 +16,8 @@ pub struct Trak {
     pub meta: Option<Meta>, // TODO is this suppose to be here?
     pub mdia: Mdia,
     pub udta: Option<Udta>,
+    #[cfg(feature = "fault-tolerant")]
+    pub unexpected: Vec<Any>,
 }
 
 impl Atom for Trak {
diff --git a/src/moov/udta/mod.rs b/src/moov/udta/mod.rs
index 2a550f0..3324b19 100644
--- a/src/moov/udta/mod.rs
+++ b/src/moov/udta/mod.rs
@@ -4,11 +4,13 @@ pub use skip::*;
 
 use crate::*;
 
-#[derive(Debug, Clone, PartialEq, Eq, Default)]
+#[derive(Debug, Clone, PartialEq, Default)]
 #[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
 pub struct Udta {
     pub meta: Option<Meta>,
     pub skip: Option<Skip>,
+    #[cfg(feature = "fault-tolerant")]
+    pub unexpected: Vec<Any>,
 }
 
 impl Atom for Udta {
@@ -30,6 +32,8 @@ mod tests {
         let expected = Udta {
             meta: None,
             skip: None,
+            #[cfg(feature = "fault-tolerant")]
+            unexpected: vec![],
         };
 
         let mut buf = Vec::new();
@@ -51,6 +55,8 @@ mod tests {
                 items: vec![],
             }),
             skip: None,
+            #[cfg(feature = "fault-tolerant")]
+            unexpected: vec![],
         };
 
         let mut buf = Vec::new();
diff --git a/src/test/av1.rs b/src/test/av1.rs
index 7b00be3..e93d336 100644
--- a/src/test/av1.rs
+++ b/src/test/av1.rs
@@ -111,6 +111,8 @@ fn av1() {
     assert_eq!(
         moov,
         Moov {
+            #[cfg(feature = "fault-tolerant")]
+            unexpected: vec![],
             mvhd: Mvhd {
                 creation_time: 0,
                 modification_time: 0,
@@ -133,6 +135,8 @@ fn av1() {
             },
             meta: None,
             mvex: Some(Mvex {
+                #[cfg(feature = "fault-tolerant")]
+                unexpected: vec![],
                 mehd: None,
                 trex: vec![Trex {
                     track_id: 1,
@@ -143,6 +147,8 @@ fn av1() {
                 }]
             }),
             trak: vec![Trak {
+                #[cfg(feature = "fault-tolerant")]
+                unexpected: vec![],
                 tkhd: Tkhd {
                     creation_time: 0,
                     modification_time: 0,
@@ -169,6 +175,8 @@ fn av1() {
                 edts: None,
                 meta: None,
                 mdia: Mdia {
+                    #[cfg(feature = "fault-tolerant")]
+                    unexpected: vec![],
                     mdhd: Mdhd {
                         creation_time: 0,
                         modification_time: 0,
@@ -181,6 +189,8 @@ fn av1() {
                         name: "obu@GPAC2.1-DEV-rev199-g8e29f6e8b-github_master".into()
                     },
                     minf: Minf {
+                        #[cfg(feature = "fault-tolerant")]
+                        unexpected: vec![],
                         vmhd: Some(Vmhd {
                             graphics_mode: 0,
                             op_color: RgbColor {
@@ -191,6 +201,8 @@ fn av1() {
                         }),
                         smhd: None,
                         dinf: Dinf {
+                            #[cfg(feature = "fault-tolerant")]
+                            unexpected: vec![],
                             dref: Dref {
                                 urls: vec![Url {
                                     location: "".into()
@@ -198,6 +210,8 @@ fn av1() {
                             }
                         },
                         stbl: Stbl {
+                            #[cfg(feature = "fault-tolerant")]
+                            unexpected: vec![],
                             stsd: Stsd {
                                 codecs: vec![Av01 {
                                     visual: Visual {
@@ -233,6 +247,8 @@ fn av1() {
                                     colr: None,
                                     pasp: None,
                                     taic: None,
+                                    #[cfg(feature = "fault-tolerant")]
+                                    unexpected: vec![],
                                 }
                                 .into()],
                             },
@@ -254,6 +270,8 @@ fn av1() {
                 udta: None,
             }],
             udta: Some(Udta {
+                #[cfg(feature = "fault-tolerant")]
+                unexpected: vec![],
                 meta: Some(Meta {
                     hdlr: Hdlr {
                         handler: FourCC::new(b"mdir"),
@@ -270,8 +288,12 @@ fn av1() {
     assert_eq!(
         moof,
         Moof {
+            #[cfg(feature = "fault-tolerant")]
+            unexpected: vec![],
             mfhd: Mfhd { sequence_number: 1 },
             traf: vec![Traf {
+                #[cfg(feature = "fault-tolerant")]
+                unexpected: vec![],
                 tfhd: Tfhd {
                     track_id: 1,
                     base_data_offset: None,
diff --git a/src/test/bbb.rs b/src/test/bbb.rs
index ed6382f..437ba3f 100644
--- a/src/test/bbb.rs
+++ b/src/test/bbb.rs
@@ -218,6 +218,8 @@ fn bbb() {
                     ..Default::default()
                 },
                 mdia: Mdia {
+                    #[cfg(feature = "fault-tolerant")]
+                    unexpected: vec![],
                     mdhd: Mdhd {
                         timescale: 24000,
                         language: "und".into(),
@@ -228,12 +230,16 @@ fn bbb() {
                         name: "(C) 2007 Google Inc. v08.13.2007.".into(),
                     },
                     minf: Minf {
+                        #[cfg(feature = "fault-tolerant")]
+                        unexpected: vec![],
                         smhd: None,
                         vmhd: Vmhd {
                             ..Default::default()
                         }
                         .into(),
                         dinf: Dinf {
+                            #[cfg(feature = "fault-tolerant")]
+                            unexpected: vec![],
                             dref: Dref {
                                 urls: vec![Url {
                                     location: "".into(),
@@ -270,6 +276,8 @@ fn bbb() {
                                         v_spacing: 1,
                                     }),
                                     taic: None,
+                                    #[cfg(feature = "fault-tolerant")]
+                                    unexpected: vec![],
                                 }
                                 .into()],
                             },
@@ -298,6 +306,8 @@ fn bbb() {
                     ..Default::default()
                 },
                 mdia: Mdia {
+                    #[cfg(feature = "fault-tolerant")]
+                    unexpected: vec![],
                     mdhd: Mdhd {
                         timescale: 44100,
                         language: "und".into(),
@@ -312,6 +322,8 @@ fn bbb() {
                             ..Default::default()
                         }),
                         dinf: Dinf {
+                            #[cfg(feature = "fault-tolerant")]
+                            unexpected: vec![],
                             dref: Dref {
                                 urls: vec![Url {
                                     location: "".into(),
@@ -347,6 +359,8 @@ fn bbb() {
                                     },
                                     btrt: Some(Btrt { buffer_size_db: 0, max_bitrate: 125587, avg_bitrate: 125587 }),
                                     taic: None,
+                                    #[cfg(feature = "fault-tolerant")]
+                                    unexpected: vec![],
                                 }
                                 .into()],
                             },
@@ -383,8 +397,12 @@ fn bbb() {
     assert_eq!(
         moof,
         Moof {
+            #[cfg(feature = "fault-tolerant")]
+            unexpected: vec![],
             mfhd: Mfhd { sequence_number: 1 },
             traf: vec![Traf {
+                #[cfg(feature = "fault-tolerant")]
+                unexpected: vec![],
                 tfhd: Tfhd {
                     track_id: 1,
                     sample_description_index: 1.into(),
@@ -443,8 +461,12 @@ fn bbb() {
     assert_eq!(
         moof,
         Moof {
+            #[cfg(feature = "fault-tolerant")]
+            unexpected: vec![],
             mfhd: Mfhd { sequence_number: 2 },
             traf: vec![Traf {
+                #[cfg(feature = "fault-tolerant")]
+                unexpected: vec![],
                 tfhd: Tfhd {
                     track_id: 2,
                     sample_description_index: 1.into(),
diff --git a/src/test/esds.rs b/src/test/esds.rs
index 1d294f2..45f77dd 100644
--- a/src/test/esds.rs
+++ b/src/test/esds.rs
@@ -147,6 +147,8 @@ fn esds() {
                     ..Default::default()
                 },
                 mdia: Mdia {
+                    #[cfg(feature = "fault-tolerant")]
+                    unexpected: vec![],
                     mdhd: Mdhd {
                         timescale: 12288,
                         language: "und".into(),
@@ -157,12 +159,16 @@ fn esds() {
                         name: "(C) 2007 Google Inc. v08.13.2007.".into(),
                     },
                     minf: Minf {
+                        #[cfg(feature = "fault-tolerant")]
+                        unexpected: vec![],
                         smhd: None,
                         vmhd: Vmhd {
                             ..Default::default()
                         }
                         .into(),
                         dinf: Dinf {
+                            #[cfg(feature = "fault-tolerant")]
+                            unexpected: vec![],
                             dref: Dref {
                                 urls: vec![Url {
                                     location: "".into(),
@@ -199,6 +205,8 @@ fn esds() {
                                         v_spacing: 1
                                     }),
                                     taic: None,
+                                    #[cfg(feature = "fault-tolerant")]
+                                    unexpected: vec![],
                                 }
                                 .into()],
                             },
@@ -227,6 +235,8 @@ fn esds() {
                     ..Default::default()
                 },
                 mdia: Mdia {
+                    #[cfg(feature = "fault-tolerant")]
+                    unexpected: vec![],
                     mdhd: Mdhd {
                         timescale: 44100,
                         language: "und".into(),
@@ -241,6 +251,8 @@ fn esds() {
                             ..Default::default()
                         }),
                         dinf: Dinf {
+                            #[cfg(feature = "fault-tolerant")]
+                            unexpected: vec![],
                             dref: Dref {
                                 urls: vec![Url {
                                     location: "".into(),
@@ -276,6 +288,8 @@ fn esds() {
                                     },
                                     btrt: Some(Btrt { buffer_size_db: 0, max_bitrate: 128000, avg_bitrate: 128000 }),
                                     taic: None,
+                                    #[cfg(feature = "fault-tolerant")]
+                                    unexpected: vec![],
                                 }
                                 .into()],
                             },
@@ -311,8 +325,12 @@ fn esds() {
     assert_eq!(
         moof,
         Moof {
+            #[cfg(feature = "fault-tolerant")]
+            unexpected: vec![],
             mfhd: Mfhd { sequence_number: 1 },
             traf: vec![Traf {
+                #[cfg(feature = "fault-tolerant")]
+                unexpected: vec![],
                 tfhd: Tfhd {
                     track_id: 1,
                     sample_description_index: 1.into(),
diff --git a/src/test/fault_tolerant.rs b/src/test/fault_tolerant.rs
new file mode 100644
index 0000000..73e6754
--- /dev/null
+++ b/src/test/fault_tolerant.rs
@@ -0,0 +1,226 @@
+use crate::*;
+
+/// Test that fault-tolerant feature works as expected
+/// When enabled: unexpected boxes are collected
+/// When disabled: unexpected boxes cause an error
+#[test]
+fn test_fault_tolerant_behavior() {
+    // Create a buffer with a Moov box containing an unexpected child box
+    // Moov structure: mvhd (required) + an unknown/unexpected box
+    let mut buf = Vec::new();
+
+    // First encode a valid Moov with mvhd
+    let moov = Moov {
+        mvhd: Mvhd {
+            creation_time: 0,
+            modification_time: 0,
+            timescale: 1000,
+            duration: 0,
+            rate: 1.into(),
+            volume: 1.into(),
+            next_track_id: 1,
+            ..Default::default()
+        },
+        meta: None,
+        mvex: None,
+        trak: vec![],
+        udta: None,
+        #[cfg(feature = "fault-tolerant")]
+        unexpected: vec![],
+    };
+
+    // Encode the moov
+    moov.encode(&mut buf).unwrap();
+
+    // Now manually insert an unexpected box into the moov
+    // We'll use 'mdat' which is a known box type but NOT expected inside moov
+    // This should trigger the unexpected box behavior
+    let mut moov_buf = Vec::new();
+
+    // Encode mvhd
+    moov.mvhd.encode(&mut moov_buf).unwrap();
+
+    // Add an mdat box (which is NOT a child of moov)
+    // This should be treated as unexpected
+    let mdat_data = vec![
+        0x00, 0x00, 0x00, 0x10, // size: 16 bytes
+        b'm', b'd', b'a', b't', // type: 'mdat'
+        0x01, 0x02, 0x03, 0x04, // some data
+        0x05, 0x06, 0x07, 0x08,
+    ];
+    moov_buf.extend_from_slice(&mdat_data);
+
+    // Now wrap it in a moov box
+    let mut final_buf = Vec::new();
+    let moov_size = (moov_buf.len() + 8) as u32; // +8 for size and type
+    final_buf.extend_from_slice(&moov_size.to_be_bytes());
+    final_buf.extend_from_slice(b"moov");
+    final_buf.extend_from_slice(&moov_buf);
+
+    // Try to decode the moov
+    let result = Moov::decode(&mut final_buf.as_slice());
+
+    #[cfg(feature = "fault-tolerant")]
+    {
+        // With fault-tolerant feature enabled, it should succeed
+        let decoded = result.expect("should decode successfully with fault-tolerant feature");
+
+        // Check that the unexpected box was collected
+        assert_eq!(decoded.unexpected.len(), 1, "should have 1 unexpected box");
+
+        // Verify the unexpected box
+        match &decoded.unexpected[0] {
+            Any::Mdat(mdat) => {
+                // The mdat box should be collected as unexpected
+                assert_eq!(mdat.data.len(), 8, "mdat data should be 8 bytes");
+            }
+            _ => panic!(
+                "unexpected box should be Any::Mdat variant, got: {:?}",
+                decoded.unexpected[0]
+            ),
+        }
+
+        // Other fields should be decoded correctly
+        assert_eq!(decoded.mvhd.timescale, 1000);
+        assert_eq!(decoded.trak.len(), 0);
+    }
+
+    #[cfg(not(feature = "fault-tolerant"))]
+    {
+        // Without fault-tolerant feature, it should return an error
+        assert!(
+            result.is_err(),
+            "should fail to decode without fault-tolerant feature"
+        );
+
+        // Check that it's specifically an UnexpectedBox error
+        match result.unwrap_err() {
+            Error::UnexpectedBox(kind) => {
+                assert_eq!(
+                    kind,
+                    FourCC::new(b"mdat"),
+                    "error should report 'mdat' as unexpected"
+                );
+            }
+            other => panic!("expected UnexpectedBox error, got: {:?}", other),
+        }
+    }
+}
+
+/// Test that multiple unexpected boxes are collected correctly
+#[test]
+#[cfg(feature = "fault-tolerant")]
+fn test_multiple_unexpected_boxes() {
+    // Create a moov with multiple unexpected boxes
+    let mut moov_buf = Vec::new();
+
+    // Encode mvhd
+    let mvhd = Mvhd {
+        creation_time: 0,
+        modification_time: 0,
+        timescale: 1000,
+        duration: 0,
+        rate: 1.into(),
+        volume: 1.into(),
+        next_track_id: 1,
+        ..Default::default()
+    };
+    mvhd.encode(&mut moov_buf).unwrap();
+
+    // Add first unexpected box (ftyp - not expected in moov)
+    let unexpected1 = vec![
+        0x00, 0x00, 0x00, 0x14, // size: 20 bytes
+        b'f', b't', b'y', b'p', // type: 'ftyp'
+        b'i', b's', b'o', b'm', // major brand
+        0x00, 0x00, 0x02, 0x00, // minor version
+        b'm', b'p', b'4', b'1', // compatible brand
+    ];
+    moov_buf.extend_from_slice(&unexpected1);
+
+    // Add second unexpected box (mdat - not expected in moov)
+    let unexpected2 = vec![
+        0x00, 0x00, 0x00, 0x10, // size: 16 bytes
+        b'm', b'd', b'a', b't', // type: 'mdat'
+        0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08,
+    ];
+    moov_buf.extend_from_slice(&unexpected2);
+
+    // Wrap in moov box
+    let mut final_buf = Vec::new();
+    let moov_size = (moov_buf.len() + 8) as u32;
+    final_buf.extend_from_slice(&moov_size.to_be_bytes());
+    final_buf.extend_from_slice(b"moov");
+    final_buf.extend_from_slice(&moov_buf);
+
+    // Decode
+    let decoded = Moov::decode(&mut final_buf.as_slice())
+        .expect("should decode successfully with multiple unexpected boxes");
+
+    // Verify both unexpected boxes were collected
+    assert_eq!(
+        decoded.unexpected.len(),
+        2,
+        "should have 2 unexpected boxes"
+    );
+
+    match &decoded.unexpected[0] {
+        Any::Ftyp(ftyp) => {
+            assert_eq!(ftyp.major_brand, FourCC::new(b"isom"));
+        }
+        _ => panic!(
+            "first unexpected box should be Any::Ftyp, got: {:?}",
+            decoded.unexpected[0]
+        ),
+    }
+
+    match &decoded.unexpected[1] {
+        Any::Mdat(mdat) => {
+            assert_eq!(mdat.data.len(), 8);
+        }
+        _ => panic!(
+            "second unexpected box should be Any::Mdat, got: {:?}",
+            decoded.unexpected[1]
+        ),
+    }
+}
+
+/// Test that unexpected boxes are not encoded back
+#[test]
+#[cfg(feature = "fault-tolerant")]
+fn test_unexpected_boxes_not_encoded() {
+    // Create a moov with an unexpected box
+    let moov = Moov {
+        mvhd: Mvhd {
+            creation_time: 0,
+            modification_time: 0,
+            timescale: 1000,
+            duration: 0,
+            rate: 1.into(),
+            volume: 1.into(),
+            next_track_id: 1,
+            ..Default::default()
+        },
+        meta: None,
+        mvex: None,
+        trak: vec![],
+        udta: None,
+        unexpected: vec![Any::Mdat(Mdat {
+            data: vec![0x01, 0x02, 0x03, 0x04],
+        })],
+    };
+
+    // Encode the moov
+    let mut buf = Vec::new();
+    moov.encode(&mut buf).unwrap();
+
+    // Decode it back
+    let decoded = Moov::decode(&mut buf.as_slice()).expect("should decode");
+
+    // The unexpected box should NOT be present in the decoded version
+    // because it wasn't encoded
+    assert_eq!(
+        decoded.unexpected.len(),
+        0,
+        "unexpected boxes should not be encoded"
+    );
+}
diff --git a/src/test/flac.rs b/src/test/flac.rs
index b078e9d..2fd56ef 100644
--- a/src/test/flac.rs
+++ b/src/test/flac.rs
@@ -239,6 +239,8 @@ fn flac() {
     assert_eq!(
         moov,
         Moov {
+            #[cfg(feature = "fault-tolerant")]
+            unexpected: vec![],
             mvhd: Mvhd {
                 creation_time: 3840517353,
                 modification_time: 3840517353,
@@ -261,6 +263,8 @@ fn flac() {
             },
             meta: None,
             mvex: Some(Mvex {
+                #[cfg(feature = "fault-tolerant")]
+                unexpected: vec![],
                 mehd: None,
                 trex: vec![Trex {
                     track_id: 1,
@@ -271,6 +275,8 @@ fn flac() {
                 }]
             }),
             trak: vec![Trak {
+                #[cfg(feature = "fault-tolerant")]
+                unexpected: vec![],
                 tkhd: Tkhd {
                     creation_time: 3840517353,
                     modification_time: 3840517353,
@@ -297,6 +303,8 @@ fn flac() {
                 edts: None,
                 meta: None,
                 mdia: Mdia {
+                    #[cfg(feature = "fault-tolerant")]
+                    unexpected: vec![],
                     mdhd: Mdhd {
                         creation_time: 3840517353,
                         modification_time: 3840517353,
@@ -309,9 +317,13 @@ fn flac() {
                         name: "SoundHandler".into(),
                     },
                     minf: Minf {
+                        #[cfg(feature = "fault-tolerant")]
+                        unexpected: vec![],
                         vmhd: None,
                         smhd: Some(Smhd { balance: 0.into() }),
                         dinf: Dinf {
+                            #[cfg(feature = "fault-tolerant")]
+                            unexpected: vec![],
                             dref: Dref {
                                 urls: vec![Url {
                                     location: "".into()
@@ -319,6 +331,8 @@ fn flac() {
                             }
                         },
                         stbl: Stbl {
+                            #[cfg(feature = "fault-tolerant")]
+                            unexpected: vec![],
                             stsd: Stsd {
                                 codecs: vec![Flac {
                                     audio: Audio {
@@ -353,6 +367,8 @@ fn flac() {
                                             },
                                         ],
                                     },
+                                    #[cfg(feature = "fault-tolerant")]
+                                    unexpected: vec![],
                                 }
                                 .into(),]
                             },
diff --git a/src/test/h264.rs b/src/test/h264.rs
index 9f34a17..9f4a2d1 100644
--- a/src/test/h264.rs
+++ b/src/test/h264.rs
@@ -118,6 +118,8 @@ fn avcc_ext() {
 
     let moov = Moov::decode(buf).expect("failed to decode moov");
     let expected = Moov {
+        #[cfg(feature = "fault-tolerant")]
+        unexpected: vec![],
         mvhd: Mvhd {
             creation_time: 0,
             modification_time: 0,
@@ -140,6 +142,8 @@ fn avcc_ext() {
         },
         meta: None,
         mvex: Some(Mvex {
+            #[cfg(feature = "fault-tolerant")]
+            unexpected: vec![],
             mehd: None,
             trex: vec![
                 Trex {
@@ -160,6 +164,8 @@ fn avcc_ext() {
         }),
         trak: vec![
             Trak {
+                #[cfg(feature = "fault-tolerant")]
+                unexpected: vec![],
                 tkhd: Tkhd {
                     creation_time: 0,
                     modification_time: 0,
@@ -186,6 +192,8 @@ fn avcc_ext() {
                 edts: None,
                 meta: None,
                 mdia: Mdia {
+                    #[cfg(feature = "fault-tolerant")]
+                    unexpected: vec![],
                     mdhd: Mdhd {
                         creation_time: 0,
                         modification_time: 0,
@@ -198,6 +206,8 @@ fn avcc_ext() {
                         name: "L-SMASH Video Handler".to_string(),
                     },
                     minf: Minf {
+                        #[cfg(feature = "fault-tolerant")]
+                        unexpected: vec![],
                         vmhd: Some(Vmhd {
                             graphics_mode: 0,
                             op_color: RgbColor {
@@ -208,11 +218,15 @@ fn avcc_ext() {
                         }),
                         smhd: None,
                         dinf: Dinf {
+                            #[cfg(feature = "fault-tolerant")]
+                            unexpected: vec![],
                             dref: Dref {
                                 urls: vec![Url::default()],
                             },
                         },
                         stbl: Stbl {
+                            #[cfg(feature = "fault-tolerant")]
+                            unexpected: vec![],
                             stsd: Stsd {
                                 codecs: vec![Avc1 {
                                     visual: Visual {
@@ -258,7 +272,7 @@ fn avcc_ext() {
                                         h_spacing: 1,
                                         v_spacing: 1,
                                     }),
-                                    taic: None,
+                                    ..Default::default()
                                 }
                                 .into()],
                             },
@@ -280,6 +294,8 @@ fn avcc_ext() {
                 udta: None,
             },
             Trak {
+                #[cfg(feature = "fault-tolerant")]
+                unexpected: vec![],
                 tkhd: Tkhd {
                     creation_time: 0,
                     modification_time: 0,
@@ -306,6 +322,8 @@ fn avcc_ext() {
                 edts: None,
                 meta: None,
                 mdia: Mdia {
+                    #[cfg(feature = "fault-tolerant")]
+                    unexpected: vec![],
                     mdhd: Mdhd {
                         creation_time: 0,
                         modification_time: 0,
@@ -318,14 +336,20 @@ fn avcc_ext() {
                         name: "L-SMASH Audio Handler".into(),
                     },
                     minf: Minf {
+                        #[cfg(feature = "fault-tolerant")]
+                        unexpected: vec![],
                         vmhd: None,
                         smhd: Some(Smhd::default()),
                         dinf: Dinf {
+                            #[cfg(feature = "fault-tolerant")]
+                            unexpected: vec![],
                             dref: Dref {
                                 urls: vec![Url::default()],
                             },
                         },
                         stbl: Stbl {
+                            #[cfg(feature = "fault-tolerant")]
+                            unexpected: vec![],
                             stsd: Stsd {
                                 codecs: vec![Mp4a {
                                     audio: Audio {
@@ -359,6 +383,8 @@ fn avcc_ext() {
                                         avg_bitrate: 160000,
                                     }),
                                     taic: None,
+                                    #[cfg(feature = "fault-tolerant")]
+                                    unexpected: vec![],
                                 }
                                 .into()],
                             },
@@ -381,6 +407,8 @@ fn avcc_ext() {
             },
         ],
         udta: Some(Udta {
+            #[cfg(feature = "fault-tolerant")]
+            unexpected: vec![],
             meta: None,
             skip: Some(Skip {
                 zeroed: Zeroed { size: 81 },
@@ -670,10 +698,14 @@ fn avc_encrypted_segment() {
     assert_eq!(
         moof,
         Moof {
+            #[cfg(feature = "fault-tolerant")]
+            unexpected: vec![],
             mfhd: Mfhd {
                 sequence_number: 4382715
             },
             traf: vec![Traf {
+                #[cfg(feature = "fault-tolerant")]
+                unexpected: vec![],
                 tfhd: Tfhd {
                     track_id: 1,
                     base_data_offset: None,
diff --git a/src/test/heif.rs b/src/test/heif.rs
index 05f1b91..0bd3f28 100644
--- a/src/test/heif.rs
+++ b/src/test/heif.rs
@@ -129,6 +129,8 @@ fn heif() {
                 }
                 .into(),
                 Iprp {
+                    #[cfg(feature = "fault-tolerant")]
+                    unexpected: vec![],
                     ipco: Ipco {
                         properties: vec![
                             any::Any::Hvcc(Hvcc {
@@ -410,6 +412,8 @@ fn avif() {
                 }
                 .into(),
                 Iprp {
+                    #[cfg(feature = "fault-tolerant")]
+                    unexpected: vec![],
                     ipco: Ipco {
                         properties: vec![
                             Any::Ispe(Ispe {
diff --git a/src/test/hevc.rs b/src/test/hevc.rs
index d6bdcdf..4eae917 100644
--- a/src/test/hevc.rs
+++ b/src/test/hevc.rs
@@ -211,51 +211,30 @@ fn hevc() {
         }
     );
 
-    let moov = Moov::decode(buf).expect("failed to decode moov");
-    assert_eq!(
-        moov,
-        Moov {
-            mvhd: Mvhd {
-                creation_time: 0,
-                modification_time: 0,
-                timescale: 1000,
-                duration: 0,
-                rate: 1.into(),
-                volume: 1.into(),
-                matrix: Matrix {
-                    a: 65536,
-                    b: 0,
-                    u: 0,
-                    c: 0,
-                    d: 65536,
-                    v: 0,
-                    x: 0,
-                    y: 0,
-                    w: 1073741824
-                },
-                next_track_id: 2
-            },
-            meta: None,
-            mvex: Some(Mvex {
-                mehd: None,
-                trex: vec![Trex {
-                    track_id: 1,
-                    default_sample_description_index: 1,
-                    default_sample_duration: 0,
-                    default_sample_size: 0,
-                    default_sample_flags: 0
-                }]
-            }),
-            trak: vec![Trak {
-                tkhd: Tkhd {
+    // unexpected box `fiel`
+    #[cfg(not(feature = "fault-tolerant"))]
+    {
+        let Error::UnexpectedBox(fourcc) = Moov::decode(buf).unwrap_err() else {
+            unreachable!()
+        };
+        assert_eq!(fourcc, FourCC::new(b"fiel"));
+    }
+
+    #[cfg(feature = "fault-tolerant")]
+    {
+        let moov = Moov::decode(buf).expect("failed to decode moov");
+        assert_eq!(
+            moov,
+            Moov {
+                #[cfg(feature = "fault-tolerant")]
+                unexpected: vec![],
+                mvhd: Mvhd {
                     creation_time: 0,
                     modification_time: 0,
-                    track_id: 1,
+                    timescale: 1000,
                     duration: 0,
-                    layer: 0,
-                    alternate_group: 0,
-                    enabled: true,
-                    volume: 0.into(),
+                    rate: 1.into(),
+                    volume: 1.into(),
                     matrix: Matrix {
                         a: 65536,
                         b: 0,
@@ -267,335 +246,412 @@ fn hevc() {
                         y: 0,
                         w: 1073741824
                     },
-                    width: 1920.into(),
-                    height: 1080.into()
+                    next_track_id: 2
                 },
-                edts: None,
                 meta: None,
-                mdia: Mdia {
-                    mdhd: Mdhd {
+                mvex: Some(Mvex {
+                    #[cfg(feature = "fault-tolerant")]
+                    unexpected: vec![],
+                    mehd: None,
+                    trex: vec![Trex {
+                        track_id: 1,
+                        default_sample_description_index: 1,
+                        default_sample_duration: 0,
+                        default_sample_size: 0,
+                        default_sample_flags: 0
+                    }]
+                }),
+                trak: vec![Trak {
+                    #[cfg(feature = "fault-tolerant")]
+                    unexpected: vec![],
+                    tkhd: Tkhd {
                         creation_time: 0,
                         modification_time: 0,
-                        timescale: 15360,
+                        track_id: 1,
                         duration: 0,
-                        language: "und".into()
-                    },
-                    hdlr: Hdlr {
-                        handler: b"vide".into(),
-                        name: "VideoHandler".into()
+                        layer: 0,
+                        alternate_group: 0,
+                        enabled: true,
+                        volume: 0.into(),
+                        matrix: Matrix {
+                            a: 65536,
+                            b: 0,
+                            u: 0,
+                            c: 0,
+                            d: 65536,
+                            v: 0,
+                            x: 0,
+                            y: 0,
+                            w: 1073741824
+                        },
+                        width: 1920.into(),
+                        height: 1080.into()
                     },
-                    minf: Minf {
-                        vmhd: Some(Vmhd {
-                            graphics_mode: 0,
-                            op_color: RgbColor {
-                                red: 0,
-                                green: 0,
-                                blue: 0
-                            }
-                        }),
-                        smhd: None,
-                        dinf: Dinf {
-                            dref: Dref {
-                                urls: vec![Url {
-                                    location: "".to_string()
-                                }]
-                            }
+                    edts: None,
+                    meta: None,
+                    mdia: Mdia {
+                        #[cfg(feature = "fault-tolerant")]
+                        unexpected: vec![],
+                        mdhd: Mdhd {
+                            creation_time: 0,
+                            modification_time: 0,
+                            timescale: 15360,
+                            duration: 0,
+                            language: "und".into()
+                        },
+                        hdlr: Hdlr {
+                            handler: b"vide".into(),
+                            name: "VideoHandler".into()
                         },
-                        stbl: Stbl {
-                            stsd: Stsd {
-                                codecs: vec![Hev1 {
-                                    visual: Visual {
-                                        data_reference_index: 1,
-                                        width: 1920,
-                                        height: 1080,
-                                        horizresolution: 72.into(),
-                                        vertresolution: 72.into(),
-                                        frame_count: 1,
-                                        compressor: "".into(),
-                                        depth: 24
-                                    },
-                                    hvcc: Hvcc {
-                                        configuration_version: 1,
-                                        general_profile_space: 0,
-                                        general_tier_flag: true,
-                                        general_profile_idc: 1,
-                                        general_profile_compatibility_flags: [96, 0, 0, 0],
-                                        general_constraint_indicator_flags: [144, 0, 0, 0, 0, 0],
-                                        general_level_idc: 120,
-                                        min_spatial_segmentation_idc: 0,
-                                        parallelism_type: 0,
-                                        chroma_format_idc: 1,
-                                        bit_depth_luma_minus8: 0,
-                                        bit_depth_chroma_minus8: 0,
-                                        avg_frame_rate: 0,
-                                        constant_frame_rate: 0,
-                                        num_temporal_layers: 1,
-                                        temporal_id_nested: true,
-                                        length_size_minus_one: 3,
-                                        arrays: vec![
-                                            HvcCArray {
-                                                completeness: false,
-                                                nal_unit_type: 32,
-                                                nalus: vec![vec![
-                                                    64, 1, 12, 1, 255, 255, 33, 96, 0, 0, 3, 0,
-                                                    144, 0, 0, 3, 0, 0, 3, 0, 120, 149, 152, 9
-                                                ]]
-                                            },
-                                            HvcCArray {
-                                                completeness: false,
-                                                nal_unit_type: 33,
-                                                nalus: vec![vec![
-                                                    66, 1, 1, 33, 96, 0, 0, 3, 0, 144, 0, 0, 3, 0,
-                                                    0, 3, 0, 120, 160, 3, 192, 128, 16, 229, 150,
-                                                    86, 105, 36, 202, 240, 16, 16, 0, 0, 3, 0, 16,
-                                                    0, 0, 3, 1, 224, 128
-                                                ]]
-                                            },
-                                            HvcCArray {
-                                                completeness: false,
-                                                nal_unit_type: 34,
-                                                nalus: vec![vec![68, 1, 193, 114, 180, 98, 64]]
-                                            },
-                                            HvcCArray {
-                                                completeness: false,
-                                                nal_unit_type: 39,
-                                                // It looks scary, but it's just the x265 CLI flags.
-                                                nalus: vec![vec![
-                                                    78, 1, 5, 255, 255, 255, 255, 255, 255, 255,
-                                                    115, 44, 162, 222, 9, 181, 23, 71, 219, 187,
-                                                    85, 164, 254, 127, 194, 252, 78, 120, 50, 54,
-                                                    53, 32, 40, 98, 117, 105, 108, 100, 32, 49, 53,
-                                                    49, 41, 32, 45, 32, 50, 46, 54, 43, 52, 57, 45,
-                                                    55, 50, 49, 57, 51, 55, 54, 100, 101, 52, 50,
-                                                    97, 58, 91, 87, 105, 110, 100, 111, 119, 115,
-                                                    93, 91, 71, 67, 67, 32, 55, 46, 51, 46, 48, 93,
-                                                    91, 54, 52, 32, 98, 105, 116, 93, 32, 56, 98,
-                                                    105, 116, 43, 49, 48, 98, 105, 116, 32, 45, 32,
-                                                    72, 46, 50, 54, 53, 47, 72, 69, 86, 67, 32, 99,
-                                                    111, 100, 101, 99, 32, 45, 32, 67, 111, 112,
-                                                    121, 114, 105, 103, 104, 116, 32, 50, 48, 49,
-                                                    51, 45, 50, 48, 49, 56, 32, 40, 99, 41, 32, 77,
-                                                    117, 108, 116, 105, 99, 111, 114, 101, 119, 97,
-                                                    114, 101, 44, 32, 73, 110, 99, 32, 45, 32, 104,
-                                                    116, 116, 112, 58, 47, 47, 120, 50, 54, 53, 46,
-                                                    111, 114, 103, 32, 45, 32, 111, 112, 116, 105,
-                                                    111, 110, 115, 58, 32, 99, 112, 117, 105, 100,
-                                                    61, 49, 48, 53, 48, 49, 49, 49, 32, 102, 114,
-                                                    97, 109, 101, 45, 116, 104, 114, 101, 97, 100,
-                                                    115, 61, 51, 32, 110, 117, 109, 97, 45, 112,
-                                                    111, 111, 108, 115, 61, 56, 32, 119, 112, 112,
-                                                    32, 110, 111, 45, 112, 109, 111, 100, 101, 32,
-                                                    110, 111, 45, 112, 109, 101, 32, 110, 111, 45,
-                                                    112, 115, 110, 114, 32, 110, 111, 45, 115, 115,
-                                                    105, 109, 32, 108, 111, 103, 45, 108, 101, 118,
-                                                    101, 108, 61, 50, 32, 98, 105, 116, 100, 101,
-                                                    112, 116, 104, 61, 56, 32, 105, 110, 112, 117,
-                                                    116, 45, 99, 115, 112, 61, 49, 32, 102, 112,
-                                                    115, 61, 51, 48, 47, 49, 32, 105, 110, 112,
-                                                    117, 116, 45, 114, 101, 115, 61, 49, 57, 50,
-                                                    48, 120, 49, 48, 56, 48, 32, 105, 110, 116,
-                                                    101, 114, 108, 97, 99, 101, 61, 48, 32, 116,
-                                                    111, 116, 97, 108, 45, 102, 114, 97, 109, 101,
-                                                    115, 61, 48, 32, 108, 101, 118, 101, 108, 45,
-                                                    105, 100, 99, 61, 48, 32, 104, 105, 103, 104,
-                                                    45, 116, 105, 101, 114, 61, 49, 32, 117, 104,
-                                                    100, 45, 98, 100, 61, 48, 32, 114, 101, 102,
-                                                    61, 52, 32, 110, 111, 45, 97, 108, 108, 111,
-                                                    119, 45, 110, 111, 110, 45, 99, 111, 110, 102,
-                                                    111, 114, 109, 97, 110, 99, 101, 32, 110, 111,
-                                                    45, 114, 101, 112, 101, 97, 116, 45, 104, 101,
-                                                    97, 100, 101, 114, 115, 32, 97, 110, 110, 101,
-                                                    120, 98, 32, 110, 111, 45, 97, 117, 100, 32,
-                                                    110, 111, 45, 104, 114, 100, 32, 105, 110, 102,
-                                                    111, 32, 104, 97, 115, 104, 61, 48, 32, 110,
-                                                    111, 45, 116, 101, 109, 112, 111, 114, 97, 108,
-                                                    45, 108, 97, 121, 101, 114, 115, 32, 111, 112,
-                                                    101, 110, 45, 103, 111, 112, 32, 109, 105, 110,
-                                                    45, 107, 101, 121, 105, 110, 116, 61, 50, 53,
-                                                    32, 107, 101, 121, 105, 110, 116, 61, 50, 53,
-                                                    48, 32, 103, 111, 112, 45, 108, 111, 111, 107,
-                                                    97, 104, 101, 97, 100, 61, 48, 32, 98, 102,
-                                                    114, 97, 109, 101, 115, 61, 52, 32, 98, 45, 97,
-                                                    100, 97, 112, 116, 61, 50, 32, 98, 45, 112,
-                                                    121, 114, 97, 109, 105, 100, 32, 98, 102, 114,
-                                                    97, 109, 101, 45, 98, 105, 97, 115, 61, 48, 32,
-                                                    114, 99, 45, 108, 111, 111, 107, 97, 104, 101,
-                                                    97, 100, 61, 50, 53, 32, 108, 111, 111, 107,
-                                                    97, 104, 101, 97, 100, 45, 115, 108, 105, 99,
-                                                    101, 115, 61, 52, 32, 115, 99, 101, 110, 101,
-                                                    99, 117, 116, 61, 52, 48, 32, 114, 97, 100,
-                                                    108, 61, 48, 32, 110, 111, 45, 105, 110, 116,
-                                                    114, 97, 45, 114, 101, 102, 114, 101, 115, 104,
-                                                    32, 99, 116, 117, 61, 54, 52, 32, 109, 105,
-                                                    110, 45, 99, 117, 45, 115, 105, 122, 101, 61,
-                                                    56, 32, 114, 101, 99, 116, 32, 110, 111, 45,
-                                                    97, 109, 112, 32, 109, 97, 120, 45, 116, 117,
-                                                    45, 115, 105, 122, 101, 61, 51, 50, 32, 116,
-                                                    117, 45, 105, 110, 116, 101, 114, 45, 100, 101,
-                                                    112, 116, 104, 61, 49, 32, 116, 117, 45, 105,
-                                                    110, 116, 114, 97, 45, 100, 101, 112, 116, 104,
-                                                    61, 49, 32, 108, 105, 109, 105, 116, 45, 116,
-                                                    117, 61, 48, 32, 114, 100, 111, 113, 45, 108,
-                                                    101, 118, 101, 108, 61, 50, 32, 100, 121, 110,
-                                                    97, 109, 105, 99, 45, 114, 100, 61, 48, 46, 48,
-                                                    48, 32, 110, 111, 45, 115, 115, 105, 109, 45,
-                                                    114, 100, 32, 115, 105, 103, 110, 104, 105,
-                                                    100, 101, 32, 110, 111, 45, 116, 115, 107, 105,
-                                                    112, 32, 110, 114, 45, 105, 110, 116, 114, 97,
-                                                    61, 48, 32, 110, 114, 45, 105, 110, 116, 101,
-                                                    114, 61, 48, 32, 110, 111, 45, 99, 111, 110,
-                                                    115, 116, 114, 97, 105, 110, 101, 100, 45, 105,
-                                                    110, 116, 114, 97, 32, 115, 116, 114, 111, 110,
-                                                    103, 45, 105, 110, 116, 114, 97, 45, 115, 109,
-                                                    111, 111, 116, 104, 105, 110, 103, 32, 109, 97,
-                                                    120, 45, 109, 101, 114, 103, 101, 61, 51, 32,
-                                                    108, 105, 109, 105, 116, 45, 114, 101, 102,
-                                                    115, 61, 51, 32, 108, 105, 109, 105, 116, 45,
-                                                    109, 111, 100, 101, 115, 32, 109, 101, 61, 51,
-                                                    32, 115, 117, 98, 109, 101, 61, 51, 32, 109,
-                                                    101, 114, 97, 110, 103, 101, 61, 53, 55, 32,
-                                                    116, 101, 109, 112, 111, 114, 97, 108, 45, 109,
-                                                    118, 112, 32, 119, 101, 105, 103, 104, 116,
-                                                    112, 32, 110, 111, 45, 119, 101, 105, 103, 104,
-                                                    116, 98, 32, 110, 111, 45, 97, 110, 97, 108,
-                                                    121, 122, 101, 45, 115, 114, 99, 45, 112, 105,
-                                                    99, 115, 32, 100, 101, 98, 108, 111, 99, 107,
-                                                    61, 48, 58, 48, 32, 115, 97, 111, 32, 110, 111,
-                                                    45, 115, 97, 111, 45, 110, 111, 110, 45, 100,
-                                                    101, 98, 108, 111, 99, 107, 32, 114, 100, 61,
-                                                    52, 32, 110, 111, 45, 101, 97, 114, 108, 121,
-                                                    45, 115, 107, 105, 112, 32, 114, 115, 107, 105,
-                                                    112, 32, 110, 111, 45, 102, 97, 115, 116, 45,
-                                                    105, 110, 116, 114, 97, 32, 110, 111, 45, 116,
-                                                    115, 107, 105, 112, 45, 102, 97, 115, 116, 32,
-                                                    110, 111, 45, 99, 117, 45, 108, 111, 115, 115,
-                                                    108, 101, 115, 115, 32, 110, 111, 45, 98, 45,
-                                                    105, 110, 116, 114, 97, 32, 110, 111, 45, 115,
-                                                    112, 108, 105, 116, 114, 100, 45, 115, 107,
-                                                    105, 112, 32, 114, 100, 112, 101, 110, 97, 108,
-                                                    116, 121, 61, 48, 32, 112, 115, 121, 45, 114,
-                                                    100, 61, 50, 46, 48, 48, 32, 112, 115, 121, 45,
-                                                    114, 100, 111, 113, 61, 49, 46, 48, 48, 32,
-                                                    110, 111, 45, 114, 100, 45, 114, 101, 102, 105,
-                                                    110, 101, 32, 110, 111, 45, 108, 111, 115, 115,
-                                                    108, 101, 115, 115, 32, 99, 98, 113, 112, 111,
-                                                    102, 102, 115, 61, 48, 32, 99, 114, 113, 112,
-                                                    111, 102, 102, 115, 61, 48, 32, 114, 99, 61,
-                                                    97, 98, 114, 32, 98, 105, 116, 114, 97, 116,
-                                                    101, 61, 50, 51, 50, 48, 48, 32, 113, 99, 111,
-                                                    109, 112, 61, 48, 46, 54, 48, 32, 113, 112,
-                                                    115, 116, 101, 112, 61, 52, 32, 115, 116, 97,
-                                                    116, 115, 45, 119, 114, 105, 116, 101, 61, 48,
-                                                    32, 115, 116, 97, 116, 115, 45, 114, 101, 97,
-                                                    100, 61, 48, 32, 105, 112, 114, 97, 116, 105,
-                                                    111, 61, 49, 46, 52, 48, 32, 112, 98, 114, 97,
-                                                    116, 105, 111, 61, 49, 46, 51, 48, 32, 97, 113,
-                                                    45, 109, 111, 100, 101, 61, 49, 32, 97, 113,
-                                                    45, 115, 116, 114, 101, 110, 103, 116, 104, 61,
-                                                    49, 46, 48, 48, 32, 99, 117, 116, 114, 101,
-                                                    101, 32, 122, 111, 110, 101, 45, 99, 111, 117,
-                                                    110, 116, 61, 48, 32, 110, 111, 45, 115, 116,
-                                                    114, 105, 99, 116, 45, 99, 98, 114, 32, 113,
-                                                    103, 45, 115, 105, 122, 101, 61, 51, 50, 32,
-                                                    110, 111, 45, 114, 99, 45, 103, 114, 97, 105,
-                                                    110, 32, 113, 112, 109, 97, 120, 61, 54, 57,
-                                                    32, 113, 112, 109, 105, 110, 61, 48, 32, 110,
-                                                    111, 45, 99, 111, 110, 115, 116, 45, 118, 98,
-                                                    118, 32, 115, 97, 114, 61, 49, 32, 111, 118,
-                                                    101, 114, 115, 99, 97, 110, 61, 48, 32, 118,
-                                                    105, 100, 101, 111, 102, 111, 114, 109, 97,
-                                                    116, 61, 53, 32, 114, 97, 110, 103, 101, 61,
-                                                    48, 32, 99, 111, 108, 111, 114, 112, 114, 105,
-                                                    109, 61, 50, 32, 116, 114, 97, 110, 115, 102,
-                                                    101, 114, 61, 50, 32, 99, 111, 108, 111, 114,
-                                                    109, 97, 116, 114, 105, 120, 61, 50, 32, 99,
-                                                    104, 114, 111, 109, 97, 108, 111, 99, 61, 48,
-                                                    32, 100, 105, 115, 112, 108, 97, 121, 45, 119,
-                                                    105, 110, 100, 111, 119, 61, 48, 32, 109, 97,
-                                                    120, 45, 99, 108, 108, 61, 48, 44, 48, 32, 109,
-                                                    105, 110, 45, 108, 117, 109, 97, 61, 48, 32,
-                                                    109, 97, 120, 45, 108, 117, 109, 97, 61, 50,
-                                                    53, 53, 32, 108, 111, 103, 50, 45, 109, 97,
-                                                    120, 45, 112, 111, 99, 45, 108, 115, 98, 61,
-                                                    56, 32, 118, 117, 105, 45, 116, 105, 109, 105,
-                                                    110, 103, 45, 105, 110, 102, 111, 32, 118, 117,
-                                                    105, 45, 104, 114, 100, 45, 105, 110, 102, 111,
-                                                    32, 115, 108, 105, 99, 101, 115, 61, 49, 32,
-                                                    110, 111, 45, 111, 112, 116, 45, 113, 112, 45,
-                                                    112, 112, 115, 32, 110, 111, 45, 111, 112, 116,
-                                                    45, 114, 101, 102, 45, 108, 105, 115, 116, 45,
-                                                    108, 101, 110, 103, 116, 104, 45, 112, 112,
-                                                    115, 32, 110, 111, 45, 109, 117, 108, 116, 105,
-                                                    45, 112, 97, 115, 115, 45, 111, 112, 116, 45,
-                                                    114, 112, 115, 32, 115, 99, 101, 110, 101, 99,
-                                                    117, 116, 45, 98, 105, 97, 115, 61, 48, 46, 48,
-                                                    53, 32, 110, 111, 45, 111, 112, 116, 45, 99,
-                                                    117, 45, 100, 101, 108, 116, 97, 45, 113, 112,
-                                                    32, 110, 111, 45, 97, 113, 45, 109, 111, 116,
-                                                    105, 111, 110, 32, 110, 111, 45, 104, 100, 114,
-                                                    32, 110, 111, 45, 104, 100, 114, 45, 111, 112,
-                                                    116, 32, 110, 111, 45, 100, 104, 100, 114, 49,
-                                                    48, 45, 111, 112, 116, 32, 97, 110, 97, 108,
-                                                    121, 115, 105, 115, 45, 114, 101, 117, 115,
-                                                    101, 45, 108, 101, 118, 101, 108, 61, 53, 32,
-                                                    115, 99, 97, 108, 101, 45, 102, 97, 99, 116,
-                                                    111, 114, 61, 48, 32, 114, 101, 102, 105, 110,
-                                                    101, 45, 105, 110, 116, 114, 97, 61, 48, 32,
-                                                    114, 101, 102, 105, 110, 101, 45, 105, 110,
-                                                    116, 101, 114, 61, 48, 32, 114, 101, 102, 105,
-                                                    110, 101, 45, 109, 118, 61, 48, 32, 110, 111,
-                                                    45, 108, 105, 109, 105, 116, 45, 115, 97, 111,
-                                                    32, 99, 116, 117, 45, 105, 110, 102, 111, 61,
-                                                    48, 32, 110, 111, 45, 108, 111, 119, 112, 97,
-                                                    115, 115, 45, 100, 99, 116, 32, 114, 101, 102,
-                                                    105, 110, 101, 45, 109, 118, 45, 116, 121, 112,
-                                                    101, 61, 48, 32, 99, 111, 112, 121, 45, 112,
-                                                    105, 99, 61, 49, 128
-                                                ]]
-                                            }
-                                        ]
-                                    },
-                                    btrt: Some(Btrt {
-                                        buffer_size_db: 0,
-                                        max_bitrate: 25175730,
-                                        avg_bitrate: 25175730
-                                    }),
-                                    colr: None,
-                                    pasp: Some(Pasp {
-                                        h_spacing: 1,
-                                        v_spacing: 1,
-                                    }),
-                                    taic: None,
+                        minf: Minf {
+                            #[cfg(feature = "fault-tolerant")]
+                            unexpected: vec![],
+                            vmhd: Some(Vmhd {
+                                graphics_mode: 0,
+                                op_color: RgbColor {
+                                    red: 0,
+                                    green: 0,
+                                    blue: 0
+                                }
+                            }),
+                            smhd: None,
+                            dinf: Dinf {
+                                #[cfg(feature = "fault-tolerant")]
+                                unexpected: vec![],
+                                dref: Dref {
+                                    urls: vec![Url {
+                                        location: "".to_string()
+                                    }]
                                 }
-                                .into()],
                             },
-                            stco: Some(Stco { entries: vec![] }),
-                            ..Default::default()
+                            stbl: Stbl {
+                                stsd: Stsd {
+                                    codecs: vec![Hev1 {
+                                        visual: Visual {
+                                            data_reference_index: 1,
+                                            width: 1920,
+                                            height: 1080,
+                                            horizresolution: 72.into(),
+                                            vertresolution: 72.into(),
+                                            frame_count: 1,
+                                            compressor: "".into(),
+                                            depth: 24
+                                        },
+                                        hvcc: Hvcc {
+                                            configuration_version: 1,
+                                            general_profile_space: 0,
+                                            general_tier_flag: true,
+                                            general_profile_idc: 1,
+                                            general_profile_compatibility_flags: [96, 0, 0, 0],
+                                            general_constraint_indicator_flags: [
+                                                144, 0, 0, 0, 0, 0
+                                            ],
+                                            general_level_idc: 120,
+                                            min_spatial_segmentation_idc: 0,
+                                            parallelism_type: 0,
+                                            chroma_format_idc: 1,
+                                            bit_depth_luma_minus8: 0,
+                                            bit_depth_chroma_minus8: 0,
+                                            avg_frame_rate: 0,
+                                            constant_frame_rate: 0,
+                                            num_temporal_layers: 1,
+                                            temporal_id_nested: true,
+                                            length_size_minus_one: 3,
+                                            arrays: vec![
+                                                HvcCArray {
+                                                    completeness: false,
+                                                    nal_unit_type: 32,
+                                                    nalus: vec![vec![
+                                                        64, 1, 12, 1, 255, 255, 33, 96, 0, 0, 3, 0,
+                                                        144, 0, 0, 3, 0, 0, 3, 0, 120, 149, 152, 9
+                                                    ]]
+                                                },
+                                                HvcCArray {
+                                                    completeness: false,
+                                                    nal_unit_type: 33,
+                                                    nalus: vec![vec![
+                                                        66, 1, 1, 33, 96, 0, 0, 3, 0, 144, 0, 0, 3,
+                                                        0, 0, 3, 0, 120, 160, 3, 192, 128, 16, 229,
+                                                        150, 86, 105, 36, 202, 240, 16, 16, 0, 0,
+                                                        3, 0, 16, 0, 0, 3, 1, 224, 128
+                                                    ]]
+                                                },
+                                                HvcCArray {
+                                                    completeness: false,
+                                                    nal_unit_type: 34,
+                                                    nalus: vec![vec![68, 1, 193, 114, 180, 98, 64]]
+                                                },
+                                                HvcCArray {
+                                                    completeness: false,
+                                                    nal_unit_type: 39,
+                                                    // It looks scary, but it's just the x265 CLI flags.
+                                                    nalus: vec![vec![
+                                                        78, 1, 5, 255, 255, 255, 255, 255, 255,
+                                                        255, 115, 44, 162, 222, 9, 181, 23, 71,
+                                                        219, 187, 85, 164, 254, 127, 194, 252, 78,
+                                                        120, 50, 54, 53, 32, 40, 98, 117, 105, 108,
+                                                        100, 32, 49, 53, 49, 41, 32, 45, 32, 50,
+                                                        46, 54, 43, 52, 57, 45, 55, 50, 49, 57, 51,
+                                                        55, 54, 100, 101, 52, 50, 97, 58, 91, 87,
+                                                        105, 110, 100, 111, 119, 115, 93, 91, 71,
+                                                        67, 67, 32, 55, 46, 51, 46, 48, 93, 91, 54,
+                                                        52, 32, 98, 105, 116, 93, 32, 56, 98, 105,
+                                                        116, 43, 49, 48, 98, 105, 116, 32, 45, 32,
+                                                        72, 46, 50, 54, 53, 47, 72, 69, 86, 67, 32,
+                                                        99, 111, 100, 101, 99, 32, 45, 32, 67, 111,
+                                                        112, 121, 114, 105, 103, 104, 116, 32, 50,
+                                                        48, 49, 51, 45, 50, 48, 49, 56, 32, 40, 99,
+                                                        41, 32, 77, 117, 108, 116, 105, 99, 111,
+                                                        114, 101, 119, 97, 114, 101, 44, 32, 73,
+                                                        110, 99, 32, 45, 32, 104, 116, 116, 112,
+                                                        58, 47, 47, 120, 50, 54, 53, 46, 111, 114,
+                                                        103, 32, 45, 32, 111, 112, 116, 105, 111,
+                                                        110, 115, 58, 32, 99, 112, 117, 105, 100,
+                                                        61, 49, 48, 53, 48, 49, 49, 49, 32, 102,
+                                                        114, 97, 109, 101, 45, 116, 104, 114, 101,
+                                                        97, 100, 115, 61, 51, 32, 110, 117, 109,
+                                                        97, 45, 112, 111, 111, 108, 115, 61, 56,
+                                                        32, 119, 112, 112, 32, 110, 111, 45, 112,
+                                                        109, 111, 100, 101, 32, 110, 111, 45, 112,
+                                                        109, 101, 32, 110, 111, 45, 112, 115, 110,
+                                                        114, 32, 110, 111, 45, 115, 115, 105, 109,
+                                                        32, 108, 111, 103, 45, 108, 101, 118, 101,
+                                                        108, 61, 50, 32, 98, 105, 116, 100, 101,
+                                                        112, 116, 104, 61, 56, 32, 105, 110, 112,
+                                                        117, 116, 45, 99, 115, 112, 61, 49, 32,
+                                                        102, 112, 115, 61, 51, 48, 47, 49, 32, 105,
+                                                        110, 112, 117, 116, 45, 114, 101, 115, 61,
+                                                        49, 57, 50, 48, 120, 49, 48, 56, 48, 32,
+                                                        105, 110, 116, 101, 114, 108, 97, 99, 101,
+                                                        61, 48, 32, 116, 111, 116, 97, 108, 45,
+                                                        102, 114, 97, 109, 101, 115, 61, 48, 32,
+                                                        108, 101, 118, 101, 108, 45, 105, 100, 99,
+                                                        61, 48, 32, 104, 105, 103, 104, 45, 116,
+                                                        105, 101, 114, 61, 49, 32, 117, 104, 100,
+                                                        45, 98, 100, 61, 48, 32, 114, 101, 102, 61,
+                                                        52, 32, 110, 111, 45, 97, 108, 108, 111,
+                                                        119, 45, 110, 111, 110, 45, 99, 111, 110,
+                                                        102, 111, 114, 109, 97, 110, 99, 101, 32,
+                                                        110, 111, 45, 114, 101, 112, 101, 97, 116,
+                                                        45, 104, 101, 97, 100, 101, 114, 115, 32,
+                                                        97, 110, 110, 101, 120, 98, 32, 110, 111,
+                                                        45, 97, 117, 100, 32, 110, 111, 45, 104,
+                                                        114, 100, 32, 105, 110, 102, 111, 32, 104,
+                                                        97, 115, 104, 61, 48, 32, 110, 111, 45,
+                                                        116, 101, 109, 112, 111, 114, 97, 108, 45,
+                                                        108, 97, 121, 101, 114, 115, 32, 111, 112,
+                                                        101, 110, 45, 103, 111, 112, 32, 109, 105,
+                                                        110, 45, 107, 101, 121, 105, 110, 116, 61,
+                                                        50, 53, 32, 107, 101, 121, 105, 110, 116,
+                                                        61, 50, 53, 48, 32, 103, 111, 112, 45, 108,
+                                                        111, 111, 107, 97, 104, 101, 97, 100, 61,
+                                                        48, 32, 98, 102, 114, 97, 109, 101, 115,
+                                                        61, 52, 32, 98, 45, 97, 100, 97, 112, 116,
+                                                        61, 50, 32, 98, 45, 112, 121, 114, 97, 109,
+                                                        105, 100, 32, 98, 102, 114, 97, 109, 101,
+                                                        45, 98, 105, 97, 115, 61, 48, 32, 114, 99,
+                                                        45, 108, 111, 111, 107, 97, 104, 101, 97,
+                                                        100, 61, 50, 53, 32, 108, 111, 111, 107,
+                                                        97, 104, 101, 97, 100, 45, 115, 108, 105,
+                                                        99, 101, 115, 61, 52, 32, 115, 99, 101,
+                                                        110, 101, 99, 117, 116, 61, 52, 48, 32,
+                                                        114, 97, 100, 108, 61, 48, 32, 110, 111,
+                                                        45, 105, 110, 116, 114, 97, 45, 114, 101,
+                                                        102, 114, 101, 115, 104, 32, 99, 116, 117,
+                                                        61, 54, 52, 32, 109, 105, 110, 45, 99, 117,
+                                                        45, 115, 105, 122, 101, 61, 56, 32, 114,
+                                                        101, 99, 116, 32, 110, 111, 45, 97, 109,
+                                                        112, 32, 109, 97, 120, 45, 116, 117, 45,
+                                                        115, 105, 122, 101, 61, 51, 50, 32, 116,
+                                                        117, 45, 105, 110, 116, 101, 114, 45, 100,
+                                                        101, 112, 116, 104, 61, 49, 32, 116, 117,
+                                                        45, 105, 110, 116, 114, 97, 45, 100, 101,
+                                                        112, 116, 104, 61, 49, 32, 108, 105, 109,
+                                                        105, 116, 45, 116, 117, 61, 48, 32, 114,
+                                                        100, 111, 113, 45, 108, 101, 118, 101, 108,
+                                                        61, 50, 32, 100, 121, 110, 97, 109, 105,
+                                                        99, 45, 114, 100, 61, 48, 46, 48, 48, 32,
+                                                        110, 111, 45, 115, 115, 105, 109, 45, 114,
+                                                        100, 32, 115, 105, 103, 110, 104, 105, 100,
+                                                        101, 32, 110, 111, 45, 116, 115, 107, 105,
+                                                        112, 32, 110, 114, 45, 105, 110, 116, 114,
+                                                        97, 61, 48, 32, 110, 114, 45, 105, 110,
+                                                        116, 101, 114, 61, 48, 32, 110, 111, 45,
+                                                        99, 111, 110, 115, 116, 114, 97, 105, 110,
+                                                        101, 100, 45, 105, 110, 116, 114, 97, 32,
+                                                        115, 116, 114, 111, 110, 103, 45, 105, 110,
+                                                        116, 114, 97, 45, 115, 109, 111, 111, 116,
+                                                        104, 105, 110, 103, 32, 109, 97, 120, 45,
+                                                        109, 101, 114, 103, 101, 61, 51, 32, 108,
+                                                        105, 109, 105, 116, 45, 114, 101, 102, 115,
+                                                        61, 51, 32, 108, 105, 109, 105, 116, 45,
+                                                        109, 111, 100, 101, 115, 32, 109, 101, 61,
+                                                        51, 32, 115, 117, 98, 109, 101, 61, 51, 32,
+                                                        109, 101, 114, 97, 110, 103, 101, 61, 53,
+                                                        55, 32, 116, 101, 109, 112, 111, 114, 97,
+                                                        108, 45, 109, 118, 112, 32, 119, 101, 105,
+                                                        103, 104, 116, 112, 32, 110, 111, 45, 119,
+                                                        101, 105, 103, 104, 116, 98, 32, 110, 111,
+                                                        45, 97, 110, 97, 108, 121, 122, 101, 45,
+                                                        115, 114, 99, 45, 112, 105, 99, 115, 32,
+                                                        100, 101, 98, 108, 111, 99, 107, 61, 48,
+                                                        58, 48, 32, 115, 97, 111, 32, 110, 111, 45,
+                                                        115, 97, 111, 45, 110, 111, 110, 45, 100,
+                                                        101, 98, 108, 111, 99, 107, 32, 114, 100,
+                                                        61, 52, 32, 110, 111, 45, 101, 97, 114,
+                                                        108, 121, 45, 115, 107, 105, 112, 32, 114,
+                                                        115, 107, 105, 112, 32, 110, 111, 45, 102,
+                                                        97, 115, 116, 45, 105, 110, 116, 114, 97,
+                                                        32, 110, 111, 45, 116, 115, 107, 105, 112,
+                                                        45, 102, 97, 115, 116, 32, 110, 111, 45,
+                                                        99, 117, 45, 108, 111, 115, 115, 108, 101,
+                                                        115, 115, 32, 110, 111, 45, 98, 45, 105,
+                                                        110, 116, 114, 97, 32, 110, 111, 45, 115,
+                                                        112, 108, 105, 116, 114, 100, 45, 115, 107,
+                                                        105, 112, 32, 114, 100, 112, 101, 110, 97,
+                                                        108, 116, 121, 61, 48, 32, 112, 115, 121,
+                                                        45, 114, 100, 61, 50, 46, 48, 48, 32, 112,
+                                                        115, 121, 45, 114, 100, 111, 113, 61, 49,
+                                                        46, 48, 48, 32, 110, 111, 45, 114, 100, 45,
+                                                        114, 101, 102, 105, 110, 101, 32, 110, 111,
+                                                        45, 108, 111, 115, 115, 108, 101, 115, 115,
+                                                        32, 99, 98, 113, 112, 111, 102, 102, 115,
+                                                        61, 48, 32, 99, 114, 113, 112, 111, 102,
+                                                        102, 115, 61, 48, 32, 114, 99, 61, 97, 98,
+                                                        114, 32, 98, 105, 116, 114, 97, 116, 101,
+                                                        61, 50, 51, 50, 48, 48, 32, 113, 99, 111,
+                                                        109, 112, 61, 48, 46, 54, 48, 32, 113, 112,
+                                                        115, 116, 101, 112, 61, 52, 32, 115, 116,
+                                                        97, 116, 115, 45, 119, 114, 105, 116, 101,
+                                                        61, 48, 32, 115, 116, 97, 116, 115, 45,
+                                                        114, 101, 97, 100, 61, 48, 32, 105, 112,
+                                                        114, 97, 116, 105, 111, 61, 49, 46, 52, 48,
+                                                        32, 112, 98, 114, 97, 116, 105, 111, 61,
+                                                        49, 46, 51, 48, 32, 97, 113, 45, 109, 111,
+                                                        100, 101, 61, 49, 32, 97, 113, 45, 115,
+                                                        116, 114, 101, 110, 103, 116, 104, 61, 49,
+                                                        46, 48, 48, 32, 99, 117, 116, 114, 101,
+                                                        101, 32, 122, 111, 110, 101, 45, 99, 111,
+                                                        117, 110, 116, 61, 48, 32, 110, 111, 45,
+                                                        115, 116, 114, 105, 99, 116, 45, 99, 98,
+                                                        114, 32, 113, 103, 45, 115, 105, 122, 101,
+                                                        61, 51, 50, 32, 110, 111, 45, 114, 99, 45,
+                                                        103, 114, 97, 105, 110, 32, 113, 112, 109,
+                                                        97, 120, 61, 54, 57, 32, 113, 112, 109,
+                                                        105, 110, 61, 48, 32, 110, 111, 45, 99,
+                                                        111, 110, 115, 116, 45, 118, 98, 118, 32,
+                                                        115, 97, 114, 61, 49, 32, 111, 118, 101,
+                                                        114, 115, 99, 97, 110, 61, 48, 32, 118,
+                                                        105, 100, 101, 111, 102, 111, 114, 109, 97,
+                                                        116, 61, 53, 32, 114, 97, 110, 103, 101,
+                                                        61, 48, 32, 99, 111, 108, 111, 114, 112,
+                                                        114, 105, 109, 61, 50, 32, 116, 114, 97,
+                                                        110, 115, 102, 101, 114, 61, 50, 32, 99,
+                                                        111, 108, 111, 114, 109, 97, 116, 114, 105,
+                                                        120, 61, 50, 32, 99, 104, 114, 111, 109,
+                                                        97, 108, 111, 99, 61, 48, 32, 100, 105,
+                                                        115, 112, 108, 97, 121, 45, 119, 105, 110,
+                                                        100, 111, 119, 61, 48, 32, 109, 97, 120,
+                                                        45, 99, 108, 108, 61, 48, 44, 48, 32, 109,
+                                                        105, 110, 45, 108, 117, 109, 97, 61, 48,
+                                                        32, 109, 97, 120, 45, 108, 117, 109, 97,
+                                                        61, 50, 53, 53, 32, 108, 111, 103, 50, 45,
+                                                        109, 97, 120, 45, 112, 111, 99, 45, 108,
+                                                        115, 98, 61, 56, 32, 118, 117, 105, 45,
+                                                        116, 105, 109, 105, 110, 103, 45, 105, 110,
+                                                        102, 111, 32, 118, 117, 105, 45, 104, 114,
+                                                        100, 45, 105, 110, 102, 111, 32, 115, 108,
+                                                        105, 99, 101, 115, 61, 49, 32, 110, 111,
+                                                        45, 111, 112, 116, 45, 113, 112, 45, 112,
+                                                        112, 115, 32, 110, 111, 45, 111, 112, 116,
+                                                        45, 114, 101, 102, 45, 108, 105, 115, 116,
+                                                        45, 108, 101, 110, 103, 116, 104, 45, 112,
+                                                        112, 115, 32, 110, 111, 45, 109, 117, 108,
+                                                        116, 105, 45, 112, 97, 115, 115, 45, 111,
+                                                        112, 116, 45, 114, 112, 115, 32, 115, 99,
+                                                        101, 110, 101, 99, 117, 116, 45, 98, 105,
+                                                        97, 115, 61, 48, 46, 48, 53, 32, 110, 111,
+                                                        45, 111, 112, 116, 45, 99, 117, 45, 100,
+                                                        101, 108, 116, 97, 45, 113, 112, 32, 110,
+                                                        111, 45, 97, 113, 45, 109, 111, 116, 105,
+                                                        111, 110, 32, 110, 111, 45, 104, 100, 114,
+                                                        32, 110, 111, 45, 104, 100, 114, 45, 111,
+                                                        112, 116, 32, 110, 111, 45, 100, 104, 100,
+                                                        114, 49, 48, 45, 111, 112, 116, 32, 97,
+                                                        110, 97, 108, 121, 115, 105, 115, 45, 114,
+                                                        101, 117, 115, 101, 45, 108, 101, 118, 101,
+                                                        108, 61, 53, 32, 115, 99, 97, 108, 101, 45,
+                                                        102, 97, 99, 116, 111, 114, 61, 48, 32,
+                                                        114, 101, 102, 105, 110, 101, 45, 105, 110,
+                                                        116, 114, 97, 61, 48, 32, 114, 101, 102,
+                                                        105, 110, 101, 45, 105, 110, 116, 101, 114,
+                                                        61, 48, 32, 114, 101, 102, 105, 110, 101,
+                                                        45, 109, 118, 61, 48, 32, 110, 111, 45,
+                                                        108, 105, 109, 105, 116, 45, 115, 97, 111,
+                                                        32, 99, 116, 117, 45, 105, 110, 102, 111,
+                                                        61, 48, 32, 110, 111, 45, 108, 111, 119,
+                                                        112, 97, 115, 115, 45, 100, 99, 116, 32,
+                                                        114, 101, 102, 105, 110, 101, 45, 109, 118,
+                                                        45, 116, 121, 112, 101, 61, 48, 32, 99,
+                                                        111, 112, 121, 45, 112, 105, 99, 61, 49,
+                                                        128
+                                                    ]]
+                                                }
+                                            ]
+                                        },
+                                        btrt: Some(Btrt {
+                                            buffer_size_db: 0,
+                                            max_bitrate: 25175730,
+                                            avg_bitrate: 25175730
+                                        }),
+                                        pasp: Some(Pasp {
+                                            h_spacing: 1,
+                                            v_spacing: 1,
+                                        }),
+                                        colr: None,
+                                        taic: None,
+                                        #[cfg(feature = "fault-tolerant")]
+                                        unexpected: vec![Any::Unknown(
+                                            FourCC::new(b"fiel"),
+                                            vec![1, 0]
+                                        )],
+                                    }
+                                    .into()],
+                                },
+                                stco: Some(Stco { entries: vec![] }),
+                                ..Default::default()
+                            }
                         }
-                    }
-                },
-                udta: None,
-            }],
-            udta: Some(Udta {
-                meta: Some(Meta {
-                    hdlr: Hdlr {
-                        handler: FourCC::new(b"mdir"),
-                        name: "".into()
                     },
-                    items: vec![Ilst::default().into(),],
-                }),
-                skip: None,
-            })
-        }
-    );
-
-    // Make sure the hev1 atom encodes/decodes to the exact same content.
-    let hev1 = &moov.trak[0].mdia.minf.stbl.stsd.codecs[0];
-    hev1.assert_encode_decode();
+                    udta: None,
+                }],
+                udta: Some(Udta {
+                    #[cfg(feature = "fault-tolerant")]
+                    unexpected: vec![],
+                    meta: Some(Meta {
+                        hdlr: Hdlr {
+                            handler: FourCC::new(b"mdir"),
+                            name: "".into()
+                        },
+                        items: vec![Ilst::default().into(),],
+                    }),
+                    skip: None,
+                })
+            }
+        );
 
-    let mut buf = Vec::new();
-    ftyp.encode(&mut buf).expect("failed to encode ftyp");
-    moov.encode(&mut buf).expect("failed to encode moov");
+        // Make sure the hev1 atom encodes/decodes to the exact same content.
+        // Note: We need to clear unexpected atoms because they are not encoded back
+        let mut hev1_for_test = moov.trak[0].mdia.minf.stbl.stsd.codecs[0].clone();
+        if let Codec::Hev1(ref mut hev1) = hev1_for_test {
+            hev1.unexpected.clear();
+        }
+        hev1_for_test.assert_encode_decode();
 
-    // assert_eq!(buf, ENCODED);
+        // Encode to verify encoding succeeds. Output will differ from ENCODED because
+        // unexpected boxes (like the `fiel` box) are not encoded back.
+        let mut buf = Vec::new();
+        ftyp.encode(&mut buf).expect("failed to encode ftyp");
+        moov.encode(&mut buf).expect("failed to encode moov");
+    }
 }
diff --git a/src/test/mod.rs b/src/test/mod.rs
index 09e6e0c..4b59f69 100644
--- a/src/test/mod.rs
+++ b/src/test/mod.rs
@@ -1,6 +1,7 @@
 mod av1;
 mod bbb;
 mod esds;
+mod fault_tolerant;
 mod flac;
 mod h264;
 mod heif;
diff --git a/src/test/uncompressed.rs b/src/test/uncompressed.rs
index adbd22e..3416e82 100644
--- a/src/test/uncompressed.rs
+++ b/src/test/uncompressed.rs
@@ -89,6 +89,8 @@ fn uncompressed() {
     assert_eq!(
         moov,
         Moov {
+            #[cfg(feature = "fault-tolerant")]
+            unexpected: vec![],
             mvhd: Mvhd {
                 creation_time: 3827291266,
                 modification_time: 3827291266,
@@ -112,6 +114,8 @@ fn uncompressed() {
             meta: None,
             mvex: None,
             trak: [Trak {
+                #[cfg(feature = "fault-tolerant")]
+                unexpected: vec![],
                 tkhd: Tkhd {
                     creation_time: 3827291266,
                     modification_time: 3827291266,
@@ -138,6 +142,8 @@ fn uncompressed() {
                 edts: None,
                 meta: None,
                 mdia: Mdia {
+                    #[cfg(feature = "fault-tolerant")]
+                    unexpected: vec![],
                     mdhd: Mdhd {
                         creation_time: 3827291266,
                         modification_time: 3827291266,
@@ -150,6 +156,8 @@ fn uncompressed() {
                         name: "GPAC ISO Video Handler".into(),
                     },
                     minf: Minf {
+                        #[cfg(feature = "fault-tolerant")]
+                        unexpected: vec![],
                         vmhd: Some(Vmhd {
                             graphics_mode: 0,
                             op_color: RgbColor {
@@ -160,6 +168,8 @@ fn uncompressed() {
                         }),
                         smhd: None,
                         dinf: Dinf {
+                            #[cfg(feature = "fault-tolerant")]
+                            unexpected: vec![],
                             dref: Dref {
                                 urls: vec![Url {
                                     location: "".into()
@@ -167,6 +177,8 @@ fn uncompressed() {
                             }
                         },
                         stbl: Stbl {
+                            #[cfg(feature = "fault-tolerant")]
+                            unexpected: vec![],
                             stsd: Stsd {
                                 codecs: vec![Codec::Uncv(Uncv {
                                     visual: Visual {
@@ -237,7 +249,9 @@ fn uncompressed() {
                                         avg_bitrate: 48
                                     }),
                                     ccst: None,
-                                    pasp: None
+                                    pasp: None,
+                                    #[cfg(feature = "fault-tolerant")]
+                                    unexpected: vec![],
                                 })],
                             },
                             stts: Stts {
@@ -283,6 +297,8 @@ fn uncompressed() {
             }]
             .into(),
             udta: Some(Udta {
+                #[cfg(feature = "fault-tolerant")]
+                unexpected: vec![],
                 meta: Some(Meta {
                     hdlr: Hdlr {
                         handler: FourCC::new(b"mdir"),
diff --git a/src/test/vp9.rs b/src/test/vp9.rs
index e42a137..24ed242 100644
--- a/src/test/vp9.rs
+++ b/src/test/vp9.rs
@@ -156,6 +156,8 @@ fn vp9() {
     assert_eq!(
         moov,
         Moov {
+            #[cfg(feature = "fault-tolerant")]
+            unexpected: vec![],
             mvhd: Mvhd {
                 creation_time: 3576083626,
                 modification_time: 3576083626,
@@ -193,6 +195,8 @@ fn vp9() {
                 )]
             }),
             mvex: Some(Mvex {
+                #[cfg(feature = "fault-tolerant")]
+                unexpected: vec![],
                 mehd: Some(Mehd {
                     fragment_duration: 2736000
                 }),
@@ -205,6 +209,8 @@ fn vp9() {
                 }]
             }),
             trak: vec![Trak {
+                #[cfg(feature = "fault-tolerant")]
+                unexpected: vec![],
                 tkhd: Tkhd {
                     creation_time: 3576083626,
                     modification_time: 3576083626,
@@ -231,6 +237,8 @@ fn vp9() {
                 edts: None,
                 meta: None,
                 mdia: Mdia {
+                    #[cfg(feature = "fault-tolerant")]
+                    unexpected: vec![],
                     mdhd: Mdhd {
                         creation_time: 3576083626,
                         modification_time: 3576083626,
@@ -243,6 +251,8 @@ fn vp9() {
                         name: "VideoHandler".to_string()
                     },
                     minf: Minf {
+                        #[cfg(feature = "fault-tolerant")]
+                        unexpected: vec![],
                         vmhd: Some(Vmhd {
                             graphics_mode: 0,
                             op_color: RgbColor {
@@ -253,6 +263,8 @@ fn vp9() {
                         }),
                         smhd: None,
                         dinf: Dinf {
+                            #[cfg(feature = "fault-tolerant")]
+                            unexpected: vec![],
                             dref: Dref {
                                 urls: vec![Url {
                                     location: "".to_string()
@@ -260,6 +272,8 @@ fn vp9() {
                             }
                         },
                         stbl: Stbl {
+                            #[cfg(feature = "fault-tolerant")]
+                            unexpected: vec![],
                             stsd: Stsd {
                                 codecs: vec![Vp09 {
                                     visual: Visual {
@@ -282,7 +296,9 @@ fn vp9() {
                                         transfer_characteristics: 2,
                                         matrix_coefficients: 2,
                                         codec_initialization_data: vec![]
-                                    }
+                                    },
+                                    #[cfg(feature = "fault-tolerant")]
+                                    unexpected: vec![],
                                 }
                                 .into()],
                             },