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Fix initPTS change between variants (timescale or basetime change) (#…
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…5235)

Fixes #5195
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@robwalch
robwalch committed Feb 20, 2023
1 parent a46f585 commit 94e15a2
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Showing 2 changed files with 63 additions and 19 deletions.
57 changes: 42 additions & 15 deletions src/remux/mp4-remuxer.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -147,7 +147,12 @@ export default class MP4Remuxer implements Remuxer {

if (canRemuxAvc) {
if (!this.ISGenerated) {
initSegment = this.generateIS(audioTrack, videoTrack, timeOffset);
initSegment = this.generateIS(
audioTrack,
videoTrack,
timeOffset,
accurateTimeOffset
);
}

const isVideoContiguous = this.isVideoContiguous;
Expand Down Expand Up @@ -199,7 +204,12 @@ export default class MP4Remuxer implements Remuxer {
logger.warn(
'[mp4-remuxer]: regenerate InitSegment as audio detected'
);
initSegment = this.generateIS(audioTrack, videoTrack, timeOffset);
initSegment = this.generateIS(
audioTrack,
videoTrack,
timeOffset,
accurateTimeOffset
);
}
audio = this.remuxAudio(
audioTrack,
Expand All @@ -219,7 +229,12 @@ export default class MP4Remuxer implements Remuxer {
logger.warn(
'[mp4-remuxer]: regenerate InitSegment as video detected'
);
initSegment = this.generateIS(audioTrack, videoTrack, timeOffset);
initSegment = this.generateIS(
audioTrack,
videoTrack,
timeOffset,
accurateTimeOffset
);
}
video = this.remuxVideo(
videoTrack,
Expand Down Expand Up @@ -277,13 +292,15 @@ export default class MP4Remuxer implements Remuxer {
generateIS(
audioTrack: DemuxedAudioTrack,
videoTrack: DemuxedAvcTrack,
timeOffset
timeOffset: number,
accurateTimeOffset: boolean
): InitSegmentData | undefined {
const audioSamples = audioTrack.samples;
const videoSamples = videoTrack.samples;
const typeSupported = this.typeSupported;
const tracks: TrackSet = {};
const computePTSDTS = !this._initPTS;
const _initPTS = this._initPTS;
let computePTSDTS = !_initPTS || accurateTimeOffset;
let container = 'audio/mp4';
let initPTS: number | undefined;
let initDTS: number | undefined;
Expand Down Expand Up @@ -325,9 +342,13 @@ export default class MP4Remuxer implements Remuxer {
};
if (computePTSDTS) {
timescale = audioTrack.inputTimeScale;
// remember first PTS of this demuxing context. for audio, PTS = DTS
initPTS = initDTS =
audioSamples[0].pts - Math.round(timescale * timeOffset);
if (!_initPTS || timescale !== _initPTS.timescale) {
// remember first PTS of this demuxing context. for audio, PTS = DTS
initPTS = initDTS =
audioSamples[0].pts - Math.round(timescale * timeOffset);
} else {
computePTSDTS = false;
}
}
}

Expand All @@ -347,13 +368,17 @@ export default class MP4Remuxer implements Remuxer {
};
if (computePTSDTS) {
timescale = videoTrack.inputTimeScale;
const startPTS = this.getVideoStartPts(videoSamples);
const startOffset = Math.round(timescale * timeOffset);
initDTS = Math.min(
initDTS as number,
normalizePts(videoSamples[0].dts, startPTS) - startOffset
);
initPTS = Math.min(initPTS as number, startPTS - startOffset);
if (!_initPTS || timescale !== _initPTS.timescale) {
const startPTS = this.getVideoStartPts(videoSamples);
const startOffset = Math.round(timescale * timeOffset);
initDTS = Math.min(
initDTS as number,
normalizePts(videoSamples[0].dts, startPTS) - startOffset
);
initPTS = Math.min(initPTS as number, startPTS - startOffset);
} else {
computePTSDTS = false;
}
}
}

Expand All @@ -368,6 +393,8 @@ export default class MP4Remuxer implements Remuxer {
baseTime: initDTS as number,
timescale: timescale as number,
};
} else {
initPTS = timescale = undefined;
}

return {
Expand Down
25 changes: 21 additions & 4 deletions src/remux/passthrough-remuxer.ts
View file
Original file line number Diff line number Diff line change
Expand Up @@ -122,7 +122,8 @@ class PassThroughRemuxer implements Remuxer {
videoTrack: PassthroughTrack,
id3Track: DemuxedMetadataTrack,
textTrack: DemuxedUserdataTrack,
timeOffset: number
timeOffset: number,
accurateTimeOffset: boolean
): RemuxerResult {
let { initPTS, lastEndTime } = this;
const result: RemuxerResult = {
Expand Down Expand Up @@ -167,7 +168,10 @@ class PassThroughRemuxer implements Remuxer {
}

const startDTS = getStartDTS(initData, data);
if (!initPTS) {
if (
isInvalidInitPts(initPTS, startDTS, timeOffset) ||
(initSegment.timescale !== initPTS.timescale && accurateTimeOffset)
) {
initSegment.initPTS = startDTS - timeOffset;
this.initPTS = initPTS = {
baseTime: initSegment.initPTS,
Expand All @@ -177,10 +181,10 @@ class PassThroughRemuxer implements Remuxer {

const duration = getDuration(data, initData);
const startTime = audioTrack
? startDTS - initPTS.baseTime
? startDTS - initPTS.baseTime / initPTS.timescale
: (lastEndTime as number);
const endTime = startTime + duration;
offsetStartDTS(initData, data, initPTS.baseTime);
offsetStartDTS(initData, data, initPTS.baseTime / initPTS.timescale);

if (duration > 0) {
this.lastEndTime = endTime;
Expand Down Expand Up @@ -236,6 +240,19 @@ class PassThroughRemuxer implements Remuxer {
}
}

function isInvalidInitPts(
initPTS: RationalTimestamp | null,
startDTS: number,
timeOffset: number
): initPTS is null {
if (initPTS === null) {
return true;
}
// InitPTS is invalid when it would cause start time to be negative, or distance from time offset to be more than 1 second
const startTime = startDTS - initPTS.baseTime / initPTS.timescale;
return startTime < 0 && Math.abs(startTime - timeOffset) > 1;
}

function getParsedTrackCodec(
track: InitDataTrack | undefined,
type: ElementaryStreamTypes.AUDIO | ElementaryStreamTypes.VIDEO
Expand Down

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