arcodange/mediabunny
1
0
Fork 0
mirror of https://github.com/arcodange-org/mediabunny.git synced 2026-09-27 19:03:46 +02:00
Code Issues Packages Projects Releases Wiki Activity

Fix CTS=0 in fragmented fMP4 with multiple tracks (#317)

Browse Source 
* Fix CTS=0 in fragmented fMP4 with multiple tracks

When muxing fragmented MP4 with both video and audio tracks,
compositionTimeOffset (CTS) was zero for all video samples, causing
B-frame content to display in decode order instead of presentation
order (visible judder).

Root cause: During finalize(), interleaveSamples(true) triggers
finalizeFragment() via the cross-track keyframe check in
addSampleToTrack. This writes the trun box before processTimestamps
has computed correct decodeTimestamp values, so CTS = PTS - DTS = 0.

Fix: Call processTimestamps() for all tracks at the start of
finalizeFragment(). This is safe because processTimestamps is a no-op
when the timestampProcessingQueue is empty.

Video-only fragmented muxing was unaffected because the single-track
case never triggers the cross-track keyframe check during
interleaveSamples.

Co-Authored-By: Claude Opus 4.6 <[email protected]>

* Fix the problem at the actual root

* Oopsie doopsie

---------

Co-authored-by: Claude Opus 4.6 <[email protected]>
Co-authored-by: Vanilagy <[email protected]>
This commit is contained in:
Kyle Graehl
2026-03-06 09:56:53 +00:00
committed by GitHub
co-authored by Claude Opus 4.6 Vanilagy
parent 472dc113e3
commit 6a11a1302c
4 changed files with 55 additions and 13 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/isobmff/isobmff-muxer.ts
+7 -9
View File
@@ -1245,11 +1245,13 @@ export class IsobmffMuxer extends Muxer {
override async onTrackClose(track: OutputTrack) {
const release = await this.mutex.acquire();
if (track.type === 'subtitle' && track.source._codec === 'webvtt') {
const trackData = this.trackDatas.find(x => x.track === track) as IsobmffSubtitleTrackData;
if (trackData) {
const trackData = this.trackDatas.find(x => x.track === track);
if (trackData) {
if (trackData.type === 'subtitle' && track.source._codec === 'webvtt') {
await this.processWebVTTCues(trackData, Infinity);
}
this.processTimestamps(trackData);
}
if (this.allTracksAreKnown()) {
@@ -1274,19 +1276,15 @@ export class IsobmffMuxer extends Muxer {
if (trackData.type === 'subtitle' && trackData.track.source._codec === 'webvtt') {
await this.processWebVTTCues(trackData, Infinity);
}
this.processTimestamps(trackData);
}
if (this.isFragmented) {
await this.interleaveSamples(true);
for (const trackData of this.trackDatas) {
this.processTimestamps(trackData);
}
await this.finalizeFragment(false); // Don't flush the last fragment as we will flush it with the mfra box
} else {
for (const trackData of this.trackDatas) {
this.processTimestamps(trackData);
await this.finalizeCurrentChunk(trackData);
}
}