From d29f4f33b508a7a753562032fb90e57aef22bcc4 Mon Sep 17 00:00:00 2001
From: Alakh Chandarana <36898190+alakhpc@users.noreply.github.com>
Date: Sun, 11 Jan 2026 04:05:55 -0500
Subject: [PATCH] implement fix

---
 src/matroska/matroska-demuxer.ts | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/src/matroska/matroska-demuxer.ts b/src/matroska/matroska-demuxer.ts
index db421b6..965ccf8 100644
--- a/src/matroska/matroska-demuxer.ts
+++ b/src/matroska/matroska-demuxer.ts
@@ -193,6 +193,7 @@ type InternalTrack = {
 	codecId: string | null;
 	codecPrivate: Uint8Array | null;
 	defaultDuration: number | null;
+	defaultDurationNs: number | null;
 	name: string | null;
 	languageCode: string;
 	decodingInstructions: DecodingInstruction[];
@@ -536,6 +537,13 @@ export class MatroskaDemuxer extends Demuxer {
 			this.currentSegment.timestampFactor = 1e9 / 1e6;
 		}
 
+		// Compute default duration for all tracks now that we have the timestamp factor
+		for (const track of this.currentSegment.tracks) {
+			if (track.defaultDurationNs !== null) {
+				track.defaultDuration = (this.currentSegment.timestampFactor * track.defaultDurationNs) / 1e9;
+			}
+		}
+
 		// Put default tracks first
 		this.currentSegment.tracks.sort((a, b) => Number(b.disposition.default) - Number(a.disposition.default));
 
@@ -996,6 +1004,7 @@ export class MatroskaDemuxer extends Demuxer {
 					codecId: null,
 					codecPrivate: null,
 					defaultDuration: null,
+					defaultDurationNs: null,
 					name: null,
 					languageCode: UNDETERMINED_LANGUAGE,
 					decodingInstructions: [],
@@ -1203,9 +1212,7 @@ export class MatroskaDemuxer extends Demuxer {
 
 			case EBMLId.DefaultDuration: {
 				if (!this.currentTrack) break;
-
-				this.currentTrack.defaultDuration
-					= this.currentTrack.segment.timestampFactor * readUnsignedInt(slice, size) / 1e9;
+				this.currentTrack.defaultDurationNs = readUnsignedInt(slice, size);
 			}; break;
 
 			case EBMLId.Name: {