Subtitle asset loading problem

[JamesTharakan]

The subtitle in vtt format is packaged with shakaPackager, below is the generated mpd segment. When loading in livesim2 we are getting the below error message.

   <AdaptationSet id="2" contentType="text" lang="en" segmentAlignment="true">
      <Role schemeIdUri="urn:mpeg:dash:role:2011" value="subtitle"/>
      <Representation id="2" bandwidth="990" codecs="stpp" mimeType="application/mp4">
      </Representation>
        <SegmentTemplate timescale="1000" initialization="subtitles_1/text_init.mp4" media="subtitles_1/$Number$.m4s" startNumber="1">
        </SegmentTemplate>	  
    </AdaptationSet>

level=WARN msg="Asset loading problem. Skipping" asset=11/manifest.mpd err="getRep: addRegExpAndInit: decode init: decode box moov: decode box trak: decode box mdia: decode box minf: decode box stbl: decode box stsd: child stpp size mismatch in stsd: 44 - 43"

[tobbee]

Hi @JamesTharakan,

livesim2 does not yet support wvtt subtitles. Issue #46 is about adding support for sources with wvtt segments. However, your content is not VTT but STPP (TTML) according to the manifest.

stpp should be supported. I suspect this is an issue about a zero-byte end character in a utf8list in the stpp box as decoded by mp4ff. Could you upload the init segment of the asset as an attachment? Ideally with a non-mp4 file extension like ".init" to avoid having Github convert the link into a player link.

[JamesTharakan]

Update the text_init.mp4

[JamesTharakan]

$ MP4Box -info 1.m4s
[iso file] Movie fragment but no moov (yet) - possibly broken parsing!
File is a segment - 1 movie fragments - Brand mp41 (version 0):
Fragment #1 size 377 (moof 104) {TKID 1 TFDT 0}

---

$ MP4Box -info text_init.mp4
Movie Info - 1 track - TimeScale 1000
Duration 00:00:00.000
Fragmented: yes - duration 02:09:52.000
0 fragments - 0 SegmentIndexes
Progressive (moov before mdat)
Major Brand mp41 - version 0 - compatible brands: iso8 isom mp41 dash cmfc
Created: GMT Fri Jul 26 06:24:55 2024

Movie Meta type: "ID32" - 0 resource item(s)

Track 1 Info - ID 1 - TimeScale 1000
Media Duration 00:00:00.000
Track flags: Enabled In Movie In Preview
Media Language: English (eng)
Media Samples: 0
Fragmented track: 0 samples - Media Duration 00:00:00.000
Fragment sample defaults: duration 8000 size 0 stsd 1 sync 1 padding 0 degradation_priority 0
Media Type: subt:stpp
XML Subtitle Stream - namespace http://www.w3.org/ns/ttml
Size 0 x 0 - Translation X=0 Y=0 - Layer 0
RFC6381 Codec Parameters: stpp.ttml
All samples are sync
Max sample duration: 0 / 1000

---

$ mp4dump 1.m4s
[styp] size=8+28
[sidx] size=12+32
reference_ID = 1
timescale = 1000
earliest_presentation_time = 0
first_offset = 0
[moof] size=8+96
[mfhd] size=12+4
sequence number = 1
[traf] size=8+72
[tfhd] size=12+20, flags=2003a
track ID = 1
sample description index = 1
default sample duration = 8000
default sample size = 185
default sample flags = 0
[tfdt] size=12+8, version=1
base media decode time = 0
[trun] size=12+8, flags=1
sample count = 1
data offset

---

$ mp4info 1.m4s
No movie found in the file

[tobbee]

I looked at the file with mp4ff-info and it works fine. The root problem with stpp size mismatch goes back to Eyevinn/mp4ff#228

It was solved in v0.43 of mp4ff which was included in livesim2 v1.3.0. Which version of livesim2 do you use?

[JamesTharakan]

Thanks, once I took the latest version, problem is solved.