diff --git a/DASH/IOP/impl/validateSegment.php b/DASH/IOP/impl/validateSegment.php
index 0b3c656a..14c7aee2 100644
--- a/DASH/IOP/impl/validateSegment.php
+++ b/DASH/IOP/impl/validateSegment.php
@@ -12,6 +12,6 @@
 if (!$xml) {
     return;
 }
-
-$this->validateSegmentCommon($xml);
-$this->validateSegmentOnDemand($xml);
+// TODO: we should probably romove these checks for files existance. 
+$this->validateSegmentCommon($representation);
+$this->validateSegmentOnDemand($representation);
diff --git a/DASH/IOP/impl/validateSegmentCommon.php b/DASH/IOP/impl/validateSegmentCommon.php
index 596f10de..691110e6 100644
--- a/DASH/IOP/impl/validateSegmentCommon.php
+++ b/DASH/IOP/impl/validateSegmentCommon.php
@@ -2,15 +2,17 @@
 
 global $mpdHandler, $logger;
 
+/** @var DASHIF\RepresentationInterface $representation */
+
 $selectedPeriod = $mpdHandler->getSelectedPeriod();
 $selectedAdaptation = $mpdHandler->getSelectedAdaptationSet();
 $selectedRepresentation = $mpdHandler->getSelectedRepresentation();
 
 $period = $mpdHandler->getFeatures()['Period'][$selectedPeriod];
-$adaptation_set = $period['AdaptationSet'][$selectedAdaptationSet];
-$representation = $adaptation_set['Representation'][$selectedRepresentation];
-$codecs = ($representation['codecs']) ? $representation['codecs'] : $adaptation_set['codecs'];
-$mimeType = ($representation['mimeType']) ? $representation['mimeType'] : $adaptation_set['mimeType'];
+$adaptation_set = $period['AdaptationSet'][$selectedAdaptation];
+$repinfo = $adaptation_set['Representation'][$selectedRepresentation];
+$codecs = ($repinfo['codecs']) ? $repinfo['codecs'] : $adaptation_set['codecs'];
+$mimeType = ($repinfo['mimeType']) ? $repinfo['mimeType'] : $adaptation_set['mimeType'];
 $bitstreamSwitching = ($adaptation_set['bitstreamSwitching']) ?
   $adaptation_set['bitstreamSwitching'] : $period['bitstreamSwitching'];
 
@@ -38,25 +40,25 @@
         "Representation $selectedRepresentation (codecs $codecs)."
     );
 
-    $codecBoxes = $xml->getElementsByTagName('avcC');
+    $codecBoxes = $representation->getAVCCBoxes();
     $logger->test(
         "DASH-IF IOP 4.3",
         "Section 6.2.5.2",
         "For AVC video data, if the @bitstreamswitching flag is set to true, all Representations SHALL include " .
         "Initialization Segment containing 'avcC' box",
-        $codecBoxes->length > 0,
+        $codecBoxes && count($codecBoxes) > 0,
         "FAIL",
-        $codecBoxes->length . " 'avcC' boxes found for Period $selectedPeriod Adaptation Set $selectedAdaptation " .
+        count($codecBoxes) . " 'avcC' boxes found for Period $selectedPeriod Adaptation Set $selectedAdaptation " .
         "Representation $selectedRepresentation.",
         "No 'avcC' boxes found for Period $selectedPeriod Adaptation Set $selectedAdaptation " .
         "Representation $selectedRepresentation."
     );
-    if ($codecBoxes->length > 0) {
+    if ($codecBoxes && count($codecBoxes) > 0) {
         $spsFound = false;
         $ppsFound = false;
-        $nalBoxes = $codec_box->item(0)->getElementsByTagName('NALUnit');
+        $nalBoxes = $codecBoxes[0]->NALUnits;
         foreach ($nalBoxes as $nalBox) {
-            $unitType = $nalBox->getAttribute('nal_unit_type');
+            $unitType = $nalBox->type;
             if (hexdec($unitType) == 7) {
                 $spsFound = true;
             }
@@ -93,26 +95,26 @@
         "Representation $selectedRepresentation (codecs $codecs)."
     );
 
-    $codecBoxes = $xml->getElementsByTagName('hvcC');
+    $codecBoxes = $representation->getHVCCBoxes();
     $logger->test(
         "DASH-IF IOP 4.3",
         "Section 6.2.5.2",
         "For HEVC video data, if the @bitstreamswitching flag is set to true, all Representations SHALL include " .
         "Initialization Segment containing 'hvcC' box",
-        $codecBoxes->length > 0,
+        $codecBoxes && count($codecBoxes) > 0,
         "FAIL",
-        $codecBoxes->length . " 'hvcC' boxes found for Period $selectedPeriod Adaptation Set $selectedAdaptation " .
+        count($codecBoxes) . " 'hvcC' boxes found for Period $selectedPeriod Adaptation Set $selectedAdaptation " .
         "Representation $selectedRepresentation.",
         "No 'hvcC' boxes found for Period $selectedPeriod Adaptation Set $selectedAdaptation " .
         "Representation $selectedRepresentation."
     );
-    if ($codecBoxes->length > 0) {
-        $vps_found = false;
-        $sps_found = false;
-        $pps_found = false;
-        $nalBoxes = $codecBoxes->item(0)->getElementsByTagName('NALUnit');
+    if ($codecBoxes && count($codecBoxes) > 0) {
+        $vpsFound = false;
+        $spsFound = false;
+        $ppsFound = false;
+        $nalBoxes = $codecBoxes[0]->NALUnits;
         foreach ($nalBoxes as $nalBox) {
-            $unitType = $nalBox->getAttribute('nal_unit_type');
+            $unitType = $nalBox->type;
             if ($unitType == 32) {
                 $vpsFound = true;
             }
@@ -140,7 +142,7 @@
 }
 
 if ($isAvc || $isHevc) {
-    $elstBoxes = $xml->getElementsByTagName('elst');
+    $elstBoxes = $representation->getELSTBoxes();
     $representationProfiles = $mpdHandler->getProfiles[$selectedPeriod][$selectedAdaptation][$selectedRepresentation];
     if (
         !(strpos($representationProfiles, 'http://dashif.org/guidelines/dash-if-ondemand') !== false ||
@@ -151,7 +153,7 @@
             "DASH-IF IOP 4.3",
             "Section 6.2.5.2",
             "Edit lists SHALL NOT be present in video Adaptation Sets unless they are offered in On-Demand profile",
-            $elstBoxes->length == 0,
+            !$elstBoxes || count($elstBoxes) == 0,
             "FAIL",
             "No edit lists found for Period $selectedPeriod Adaptation Set $selectedAdaptation " .
             "Representation $selectedRepresentation",
@@ -160,15 +162,15 @@
         );
     }
 
-    $trunElements = $xml->getElementsByTagName('trun');
-    $tfdtElements = $xml->getElementsByTagName('tfdt');
+    $trunElements = $representation->getTRUNBoxes();
+    $tfdtElements = $representation->getTFDTBoxes();
     $firstSampleCompTime = '';
     $firstSampleDecTime = '';
-    if ($trunElements->length > 0) {
-        $firstSampleCompTime = $xml_trun[0]->getAttribute('earliestCompositionTime');
+    if ($trunElements && count($trunElements) > 0) {
+        $firstSampleCompTime = $trunElements[0]->earliestCompositionTime;
     }
-    if ($tfdtElements->length > 0) {
-        $firstSampleDecTime = $tfdt[0]->getAttribute('baseMediaDecodeTime');
+    if ($tfdtElements && count($tfdtElements) > 0) {
+        $firstSampleDecTime = $tfdtElements[0]->baseMediaDecodeTime;
     }
 
     $logger->test(
diff --git a/DASH/IOP/impl/validateSegmentOnDemand.php b/DASH/IOP/impl/validateSegmentOnDemand.php
index 8b37d9f0..00dd72fc 100644
--- a/DASH/IOP/impl/validateSegmentOnDemand.php
+++ b/DASH/IOP/impl/validateSegmentOnDemand.php
@@ -15,17 +15,17 @@
     return;
 }
 
-$sidxBoxes = $xml->getElementsByTagName('sidx');
+$sidxBoxes = $representation->getSIDXBoxes();
 
 $logger->test(
     "DASH-IF IOP 4.3",
     "Section 3.10.3.2",
     "Only a single 'sidx' SHALL be present",
-    $sidxBoxes->length == 1,
+    $sidxBoxes && count($sidxBoxes) == 1,
     "FAIL",
     "Exactly one 'sidx' box found for Period $selectedPeriod Adaptation Set $selectedAdaptation " .
     "Representation $selectedRepresentation",
-    $sidxBoxes->length . " 'sidx' boxes found for Period $selectedPeriod Adaptation Set $selectedAdaptation " .
+    ($sidxBoxes ? count($sidxBoxes) : 0) . " 'sidx' boxes found for Period $selectedPeriod Adaptation Set $selectedAdaptation " .
     "Representation $selectedRepresentation"
 );
 
diff --git a/DASH/IOP/module.php b/DASH/IOP/module.php
index fe4fa850..35759cdc 100644
--- a/DASH/IOP/module.php
+++ b/DASH/IOP/module.php
@@ -66,22 +66,32 @@ private function validateMPDMixedOnDemand()
     public function hookRepresentation()
     {
         parent::hookRepresentation();
-        $this->validateSegment();
+        global $validatorWrapper, $mpdHandler;
+        $thisRepresentation = [
+            $mpdHandler->getSelectedPeriod(),
+            $mpdHandler->getSelectedAdaptationSet(),
+            $mpdHandler->getSelectedRepresentation()
+        ];
+        $validatorWrapper->analyzeSingle(
+            $thisRepresentation,
+            $this,
+            'validateSegment'
+        );
     }
 
-    private function validateSegment()
+    public function validateSegment($representation)
     {
-        include 'impl/validateSegment.php';
+        return include 'impl/validateSegment.php';
     }
 
-    private function validateSegmentCommon($xml)
+    public function validateSegmentCommon($representation)
     {
-        include 'impl/validateSegmentCommon.php';
+        return include 'impl/validateSegmentCommon.php';
     }
 
-    private function validateSegmentOnDemand($xml)
+    public function validateSegmentOnDemand($representation)
     {
-        include 'impl/validateSegmentOnDemand.php';
+        return include 'impl/validateSegmentOnDemand.php';
     }
 
     public function hookAdaptationSet()
diff --git a/Utils/RepresentationInterface.php b/Utils/RepresentationInterface.php
index 95f88186..573b1b9f 100644
--- a/Utils/RepresentationInterface.php
+++ b/Utils/RepresentationInterface.php
@@ -153,4 +153,35 @@ public function hasBox($boxName)
     {
         return false;
     }
+
+    public function getAVCCBoxes(): array|null
+    {
+        return null;
+    }
+
+    public function getHVCCBoxes(): array|null
+    {
+        return null;
+    }
+
+    public function getELSTBoxes(): array|null
+    {
+        return null;
+    }
+
+    public function getTRUNBoxes(): array|null
+    {
+        return null;
+    }
+
+    public function getTFDTBoxes(): array|null
+    {
+        return null;
+    }
+        
+    public function getSIDXBoxes(): array|null
+    {
+        return null;
+    }
+
 }
diff --git a/Utils/boxes/avccbox.php b/Utils/boxes/avccbox.php
new file mode 100644
index 00000000..eed47f63
--- /dev/null
+++ b/Utils/boxes/avccbox.php
@@ -0,0 +1,12 @@
+<?php
+
+namespace DASHIF\Boxes;
+
+class AVCCBox
+{
+    public function __construct()
+    {
+        $this->NALUnits = array(); // array of NALUnit objects
+    }
+    public $NALUnits;
+}
\ No newline at end of file
diff --git a/Utils/boxes/elstbox.php b/Utils/boxes/elstbox.php
new file mode 100644
index 00000000..e49d6e98
--- /dev/null
+++ b/Utils/boxes/elstbox.php
@@ -0,0 +1,11 @@
+<?php
+
+namespace DASHIF\Boxes;
+
+class ELSTBox
+{
+    public function __construct()
+    {
+        // No fields needed for current logic (just presence/count)
+    }
+}
\ No newline at end of file
diff --git a/Utils/boxes/hvccbox.php b/Utils/boxes/hvccbox.php
new file mode 100644
index 00000000..fecec39f
--- /dev/null
+++ b/Utils/boxes/hvccbox.php
@@ -0,0 +1,12 @@
+<?php
+
+namespace DASHIF\Boxes;
+
+class HVCCBox
+{
+    public function __construct()
+    {
+        $this->NALUnits = array(); // array of NALUnit objects
+    }
+    public $NALUnits;
+}
\ No newline at end of file
diff --git a/Utils/boxes/nalunitbox.php b/Utils/boxes/nalunitbox.php
new file mode 100644
index 00000000..eb325635
--- /dev/null
+++ b/Utils/boxes/nalunitbox.php
@@ -0,0 +1,12 @@
+<?php
+
+namespace DASHIF\Boxes;
+
+class NALUnit
+{
+    public function __construct()
+    {
+        $this->type = null; 
+    }
+    public $type;
+}
\ No newline at end of file
diff --git a/Utils/boxes/sidxbox.php b/Utils/boxes/sidxbox.php
new file mode 100644
index 00000000..9450eac4
--- /dev/null
+++ b/Utils/boxes/sidxbox.php
@@ -0,0 +1,11 @@
+<?php
+
+namespace DASHIF\Boxes;
+
+class SIDXBox
+{
+    public function __construct()
+    {
+        // No fields needed for current logic (just presence/count)
+    }
+}
\ No newline at end of file
diff --git a/Utils/boxes/tdtftbox.php b/Utils/boxes/tdtftbox.php
new file mode 100644
index 00000000..6f91a03c
--- /dev/null
+++ b/Utils/boxes/tdtftbox.php
@@ -0,0 +1,12 @@
+<?php
+
+namespace DASHIF\Boxes;
+
+class TFDTBox
+{
+    public function __construct()
+    {
+        $this->baseMediaDecodeTime = null; 
+    }
+    public $baseMediaDecodeTime;
+}
\ No newline at end of file
diff --git a/Utils/boxes/trunbox.php b/Utils/boxes/trunbox.php
new file mode 100644
index 00000000..945d3a26
--- /dev/null
+++ b/Utils/boxes/trunbox.php
@@ -0,0 +1,12 @@
+<?php
+
+namespace DASHIF\Boxes;
+
+class TRUNBox
+{
+    public function __construct()
+    {
+        $this->earliestCompositionTime = null; 
+    }
+    public $earliestCompositionTime;
+}
\ No newline at end of file
diff --git a/Utils/validators/isoSegmentRepresentation.php b/Utils/validators/isoSegmentRepresentation.php
index 228d9e36..49715c04 100644
--- a/Utils/validators/isoSegmentRepresentation.php
+++ b/Utils/validators/isoSegmentRepresentation.php
@@ -325,4 +325,96 @@ public function getFragmentDurations(): array|null
         }
         return $res;
     }
+    public function getAVCCBoxes(): array|null
+    {
+        $res = array();
+        if ($this->payload) {
+            $avcCNodes = $this->payload->getElementsByTagName('avcC');
+            foreach ($avcCNodes as $node) {
+                $box = new Boxes\AVCCBox();
+                $nalUnits = $node->getElementsByTagName('NALUnit');
+                foreach ($nalUnits as $nalNode) {
+                    $nal = new Boxes\NALUnit();
+                    $nal->type = $nalNode->getAttribute('nal_unit_type');
+                    $box->NALUnits[] = $nal;
+                }
+                $res[] = $box;
+            }
+        }
+        return $res;
+    }
+
+    public function getHVCCBoxes(): array|null
+    {
+        $res = array();
+        if ($this->payload) {
+            $hvccNodes = $this->payload->getElementsByTagName('hvcC');
+            foreach ($hvccNodes as $node) {
+                $box = new Boxes\HVCCBox();
+                $nalUnits = $node->getElementsByTagName('NALUnit');
+                foreach ($nalUnits as $nalNode) {
+                    $nal = new Boxes\NALUnit();
+                    $nal->type = $nalNode->getAttribute('nal_unit_type');
+                    $box->NALUnits[] = $nal;
+                }
+                $res[] = $box;
+            }
+        }
+        return $res;
+    }
+
+    public function getELSTBoxes(): array|null
+    {
+        $res = array();
+        if ($this->payload) {
+            $elstNodes = $this->payload->getElementsByTagName('elst');
+            foreach ($elstNodes as $node) {
+                $box = new Boxes\ELSTBox();
+                $res[] = $box;
+            }
+        }
+        return $res;
+    }
+
+    public function getTRUNBoxes(): array|null
+    {
+        $res = array();
+        if ($this->payload) {
+            $trunNodes = $this->payload->getElementsByTagName('trun');
+            foreach ($trunNodes as $node) {
+                $box = new Boxes\TRUNBox();
+                $box->earliestCompositionTime = $node->getAttribute('earliestCompositionTime');
+                $res[] = $box;
+            }
+        }
+        return $res;
+    }
+
+    public function getTFDTBoxes(): array|null
+    {
+        $res = array();
+        if ($this->payload) {
+            $tfdtNodes = $this->payload->getElementsByTagName('tfdt');
+            foreach ($tfdtNodes as $node) {
+                $box = new Boxes\TFDTBox();
+                $box->baseMediaDecodeTime = $node->getAttribute('baseMediaDecodeTime');
+                $res[] = $box;
+            }
+        }
+        return $res;
+    }
+
+    public function getSIDXBoxes(): array|null
+    {
+        $res = array();
+        if ($this->payload) {
+            $sidxNodes = $this->payload->getElementsByTagName('sidx');
+            foreach ($sidxNodes as $node) {
+                $box = new \DASHIF\Boxes\SIDXBox();
+                // Add attribute extraction here
+                $res[] = $box;
+            }
+        }
+        return $res;
+    }
 }