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Improve ISOBMFF demuxer to support fragments without a key frame

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This commit is contained in:
Vanilagy
2025-07-11 10:57:24 +02:00
parent 514a533445
commit 14ad80df5d
2 changed files with 52 additions and 31 deletions
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src/isobmff/isobmff-demuxer.ts
+45 -19
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@@ -75,6 +75,7 @@ type InternalTrack = {
fragmentLookupTable: FragmentLookupTableEntry[] | null;
currentFragmentState: FragmentTrackState | null;
fragments: Fragment[];
fragmentsWithKeyFrame: Fragment[];
/** The segment durations of all edit list entries leading up to the main one (from which the offset is taken.) */
editListPreviousSegmentDurations: number;
/** The media time offset of the main edit list entry (with media time !== -1) */
@@ -168,6 +169,7 @@ type FragmentTrackState = {
type FragmentTrackData = {
startTimestamp: number;
endTimestamp: number;
firstKeyFrameTimestamp: number | null;
samples: FragmentTrackSample[];
presentationTimestamps: {
presentationTimestamp: number;
@@ -608,6 +610,7 @@ export class IsobmffDemuxer extends Demuxer {
fragmentLookupTable: null,
currentFragmentState: null,
fragments: [],
fragmentsWithKeyFrame: [],
editListPreviousSegmentDurations: 0,
editListOffset: 0,
} satisfies InternalTrack as InternalTrack;
@@ -1665,6 +1668,16 @@ export class IsobmffDemuxer extends Demuxer {
);
this.currentTrack.fragments.splice(insertionIndex + 1, 0, this.currentFragment);
const hasKeyFrame = trackData.firstKeyFrameTimestamp !== null;
if (hasKeyFrame) {
const insertionIndex = binarySearchLessOrEqual(
this.currentTrack.fragmentsWithKeyFrame,
this.currentFragment.moofOffset,
x => x.moofOffset,
);
this.currentTrack.fragmentsWithKeyFrame.splice(insertionIndex + 1, 0, this.currentFragment);
}
const { currentFragmentState } = this.currentTrack;
assert(currentFragmentState);
@@ -1801,6 +1814,7 @@ export class IsobmffDemuxer extends Demuxer {
const trackData: FragmentTrackData = {
startTimestamp: 0,
endTimestamp: 0,
firstKeyFrameTimestamp: null,
samples: [],
presentationTimestamps: [],
startTimestampIsFinal: false,
@@ -1862,13 +1876,19 @@ export class IsobmffDemuxer extends Demuxer {
.map((x, i) => ({ presentationTimestamp: x.presentationTimestamp, sampleIndex: i }))
.sort((a, b) => a.presentationTimestamp - b.presentationTimestamp);
// Update sample durations based on presentation order
for (let i = 0; i < trackData.presentationTimestamps.length - 1; i++) {
const current = trackData.presentationTimestamps[i]!;
const next = trackData.presentationTimestamps[i + 1]!;
for (let i = 0; i < trackData.presentationTimestamps.length; i++) {
const currentEntry = trackData.presentationTimestamps[i]!;
const currentSample = trackData.samples[currentEntry.sampleIndex]!;
const duration = next.presentationTimestamp - current.presentationTimestamp;
trackData.samples[current.sampleIndex]!.duration = duration;
if (trackData.firstKeyFrameTimestamp === null && currentSample.isKeyFrame) {
trackData.firstKeyFrameTimestamp = currentSample.presentationTimestamp;
}
if (i < trackData.presentationTimestamps.length - 1) {
// Update sample durations based on presentation order
const nextEntry = trackData.presentationTimestamps[i + 1]!;
currentSample.duration = nextEntry.presentationTimestamp - currentEntry.presentationTimestamp;
}
}
const firstSample = trackData.samples[trackData.presentationTimestamps[0]!.sampleIndex]!;
@@ -2105,13 +2125,13 @@ abstract class IsobmffTrackBacking implements InputTrackBacking {
correctSampleFound: true,
};
} else {
// Walk the list of fragments until we find the next fragment for this track
// Walk the list of fragments until we find the next fragment for this track with a key frame
let currentFragment = locationInFragment.fragment;
while (currentFragment.nextFragment) {
currentFragment = currentFragment.nextFragment;
const trackData = currentFragment.trackData.get(this.internalTrack.id);
if (trackData) {
if (trackData && trackData.firstKeyFrameTimestamp !== null) {
const fragmentIndex = binarySearchExact(
this.internalTrack.fragments,
currentFragment.moofOffset,
@@ -2120,9 +2140,7 @@ abstract class IsobmffTrackBacking implements InputTrackBacking {
assert(fragmentIndex !== -1);
const keyFrameIndex = trackData.samples.findIndex(x => x.isKeyFrame);
if (keyFrameIndex === -1) {
throw new Error('Not supported: Fragment does not contain key sample.');
}
assert(keyFrameIndex !== -1); // There must be one
return {
fragmentIndex,
@@ -2262,26 +2280,34 @@ abstract class IsobmffTrackBacking implements InputTrackBacking {
}
private findKeySampleInFragmentsForTimestamp(timestampInTimescale: number) {
const fragmentIndex = binarySearchLessOrEqual(
const indexInKeyFrameFragments = binarySearchLessOrEqual(
// This array is technically not sorted by start timestamp, but for any reasonable file, it basically is.
this.internalTrack.fragments,
this.internalTrack.fragmentsWithKeyFrame,
timestampInTimescale,
x => x.trackData.get(this.internalTrack.id)!.startTimestamp,
);
let fragmentIndex = -1;
let sampleIndex = -1;
let correctSampleFound = false;
if (fragmentIndex !== -1) {
const fragment = this.internalTrack.fragments[fragmentIndex]!;
if (indexInKeyFrameFragments !== -1) {
const fragment = this.internalTrack.fragmentsWithKeyFrame[indexInKeyFrameFragments]!;
// Now, let's find the actual index of the fragment in the list of ALL fragments, not just key frame ones
fragmentIndex = binarySearchExact(
this.internalTrack.fragments,
fragment.moofOffset,
x => x.moofOffset,
);
assert(fragmentIndex !== -1);
const trackData = fragment.trackData.get(this.internalTrack.id)!;
const index = findLastIndex(trackData.presentationTimestamps, (x) => {
const sample = trackData.samples[x.sampleIndex]!;
return sample.isKeyFrame && x.presentationTimestamp <= timestampInTimescale;
});
if (index === -1) {
throw new Error('Not supported: Fragment does not begin with a key sample.');
}
assert(index !== -1); // It's a key frame fragment, so there must be a key frame
const entry = trackData.presentationTimestamps[index]!;
sampleIndex = entry.sampleIndex;