src/remux/mp4-remuxer.js
/**
* fMP4 remuxer
*/
import AAC from './aac-helper';
import MP4 from './mp4-generator';
import Event from '../events';
import { ErrorTypes, ErrorDetails } from '../errors';
import { toMsFromMpegTsClock, toMpegTsClockFromTimescale } from '../utils/timescale-conversion';
import { logger } from '../utils/logger';
const MAX_SILENT_FRAME_DURATION_90KHZ = toMpegTsClockFromTimescale(10);
const PTS_DTS_SHIFT_TOLERANCE_90KHZ = toMpegTsClockFromTimescale(0.2);
let chromeVersion = null;
class MP4Remuxer {
constructor (observer, config, typeSupported, vendor) {
this.observer = observer;
this.config = config;
this.typeSupported = typeSupported;
this.ISGenerated = false;
if (chromeVersion === null) {
const result = navigator.userAgent.match(/Chrome\/(\d+)/i);
chromeVersion = result ? parseInt(result[1]) : 0;
}
}
destroy () {
}
resetTimeStamp (defaultTimeStamp) {
this._initPTS = this._initDTS = defaultTimeStamp;
}
resetInitSegment () {
this.ISGenerated = false;
}
getVideoStartPts (videoSamples) {
let rolloverDetected = false;
const startPTS = videoSamples.reduce((minPTS, sample) => {
const delta = sample.pts - minPTS;
if (delta < -4294967296) { // 2^32, see PTSNormalize for reasoning, but we're hitting a rollover here, and we don't want that to impact the timeOffset calculation
rolloverDetected = true;
return PTSNormalize(minPTS, sample.pts);
} else if (delta > 0) {
return minPTS;
} else {
return sample.pts;
}
}, videoSamples[0].pts);
if (rolloverDetected) {
logger.debug('PTS rollover detected');
}
return startPTS;
}
remux (audioTrack, videoTrack, id3Track, textTrack, timeOffset, contiguous, accurateTimeOffset) {
// generate Init Segment if needed
if (!this.ISGenerated) {
this.generateIS(audioTrack, videoTrack, timeOffset);
}
if (this.ISGenerated) {
const nbAudioSamples = audioTrack.samples.length;
const nbVideoSamples = videoTrack.samples.length;
let audioTimeOffset = timeOffset;
let videoTimeOffset = timeOffset;
if (nbAudioSamples && nbVideoSamples) {
// timeOffset is expected to be the offset of the first timestamp of this fragment (first DTS)
// if first audio DTS is not aligned with first video DTS then we need to take that into account
// when providing timeOffset to remuxAudio / remuxVideo. if we don't do that, there might be a permanent / small
// drift between audio and video streams
const startPTS = this.getVideoStartPts(videoTrack.samples);
const tsDelta = PTSNormalize(audioTrack.samples[0].pts, startPTS) - startPTS;
const audiovideoTimestampDelta = tsDelta / videoTrack.inputTimeScale;
audioTimeOffset += Math.max(0, audiovideoTimestampDelta);
videoTimeOffset += Math.max(0, -audiovideoTimestampDelta);
}
// Purposefully remuxing audio before video, so that remuxVideo can use nextAudioPts, which is
// calculated in remuxAudio.
// logger.log('nb AAC samples:' + audioTrack.samples.length);
if (nbAudioSamples) {
// if initSegment was generated without video samples, regenerate it again
if (!audioTrack.timescale) {
logger.warn('regenerate InitSegment as audio detected');
this.generateIS(audioTrack, videoTrack, timeOffset);
}
let audioData = this.remuxAudio(audioTrack, audioTimeOffset, contiguous, accurateTimeOffset, videoTimeOffset);
// logger.log('nb AVC samples:' + videoTrack.samples.length);
if (nbVideoSamples) {
let audioTrackLength;
if (audioData) {
audioTrackLength = audioData.endPTS - audioData.startPTS;
}
// if initSegment was generated without video samples, regenerate it again
if (!videoTrack.timescale) {
logger.warn('regenerate InitSegment as video detected');
this.generateIS(audioTrack, videoTrack, timeOffset);
}
this.remuxVideo(videoTrack, videoTimeOffset, contiguous, audioTrackLength);
}
} else {
// logger.log('nb AVC samples:' + videoTrack.samples.length);
if (nbVideoSamples) {
let videoData = this.remuxVideo(videoTrack, videoTimeOffset, contiguous, 0);
if (videoData && audioTrack.codec) {
this.remuxEmptyAudio(audioTrack, audioTimeOffset, contiguous, videoData);
}
}
}
}
// logger.log('nb ID3 samples:' + audioTrack.samples.length);
if (id3Track.samples.length) {
this.remuxID3(id3Track, timeOffset);
}
// logger.log('nb ID3 samples:' + audioTrack.samples.length);
if (textTrack.samples.length) {
this.remuxText(textTrack, timeOffset);
}
// notify end of parsing
this.observer.trigger(Event.FRAG_PARSED);
}
generateIS (audioTrack, videoTrack, timeOffset) {
let observer = this.observer,
audioSamples = audioTrack.samples,
videoSamples = videoTrack.samples,
typeSupported = this.typeSupported,
container = 'audio/mp4',
tracks = {},
data = { tracks },
computePTSDTS = (this._initPTS === undefined),
initPTS, initDTS;
if (computePTSDTS) {
initPTS = initDTS = Infinity;
}
if (audioTrack.config && audioSamples.length) {
// let's use audio sampling rate as MP4 time scale.
// rationale is that there is a integer nb of audio frames per audio sample (1024 for AAC)
// using audio sampling rate here helps having an integer MP4 frame duration
// this avoids potential rounding issue and AV sync issue
audioTrack.timescale = audioTrack.samplerate;
logger.log(`audio sampling rate : ${audioTrack.samplerate}`);
if (!audioTrack.isAAC) {
if (typeSupported.mpeg) { // Chrome and Safari
container = 'audio/mpeg';
audioTrack.codec = '';
} else if (typeSupported.mp3) { // Firefox
audioTrack.codec = 'mp3';
}
}
tracks.audio = {
container: container,
codec: audioTrack.codec,
initSegment: !audioTrack.isAAC && typeSupported.mpeg ? new Uint8Array() : MP4.initSegment([audioTrack]),
metadata: {
channelCount: audioTrack.channelCount
}
};
if (computePTSDTS) {
// remember first PTS of this demuxing context. for audio, PTS = DTS
initPTS = initDTS = audioSamples[0].pts - Math.round(audioTrack.inputTimeScale * timeOffset);
}
}
if (videoTrack.sps && videoTrack.pps && videoSamples.length) {
// let's use input time scale as MP4 video timescale
// we use input time scale straight away to avoid rounding issues on frame duration / cts computation
const inputTimeScale = videoTrack.inputTimeScale;
videoTrack.timescale = inputTimeScale;
tracks.video = {
container: 'video/mp4',
codec: videoTrack.codec,
initSegment: MP4.initSegment([videoTrack]),
metadata: {
width: videoTrack.width,
height: videoTrack.height
}
};
if (computePTSDTS) {
const startPTS = this.getVideoStartPts(videoSamples);
const startOffset = Math.round(inputTimeScale * timeOffset);
initDTS = Math.min(initDTS, PTSNormalize(videoSamples[0].dts, startPTS) - startOffset);
initPTS = Math.min(initPTS, startPTS - startOffset);
this.observer.trigger(Event.INIT_PTS_FOUND, { initPTS: initPTS, timescale: inputTimeScale });
}
} else if (computePTSDTS && tracks.audio) {
// initPTS found for audio-only stream with main and alt audio
this.observer.trigger(Event.INIT_PTS_FOUND, { initPTS: initPTS, timescale: audioTrack.inputTimeScale });
}
if (Object.keys(tracks).length) {
observer.trigger(Event.FRAG_PARSING_INIT_SEGMENT, data);
this.ISGenerated = true;
if (computePTSDTS) {
this._initPTS = initPTS;
this._initDTS = initDTS;
}
} else {
observer.trigger(Event.ERROR, { type: ErrorTypes.MEDIA_ERROR, details: ErrorDetails.FRAG_PARSING_ERROR, fatal: false, reason: 'no audio/video samples found' });
}
}
remuxVideo (track, timeOffset, contiguous, audioTrackLength) {
const timeScale = track.timescale;
const inputSamples = track.samples;
const outputSamples = [];
const nbSamples = inputSamples.length;
const initPTS = this._initPTS;
let offset = 8;
let mp4SampleDuration;
let mdat;
let moof;
let firstDTS;
let lastDTS;
let minPTS = Number.POSITIVE_INFINITY;
let maxPTS = Number.NEGATIVE_INFINITY;
let ptsDtsShift = 0;
let sortSamples = false;
// if parsed fragment is contiguous with last one, let's use last DTS value as reference
let nextAvcDts = this.nextAvcDts;
if (nbSamples === 0) {
return;
}
if (!contiguous) {
const pts = timeOffset * timeScale;
const cts = inputSamples[0].pts - PTSNormalize(inputSamples[0].dts, inputSamples[0].pts);
// if not contiguous, let's use target timeOffset
nextAvcDts = pts - cts;
}
// PTS is coded on 33bits, and can loop from -2^32 to 2^32
// PTSNormalize will make PTS/DTS value monotonic, we use last known DTS value as reference value
for (let i = 0; i < nbSamples; i++) {
const sample = inputSamples[i];
sample.pts = PTSNormalize(sample.pts - initPTS, nextAvcDts);
sample.dts = PTSNormalize(sample.dts - initPTS, nextAvcDts);
if (sample.dts > sample.pts) {
ptsDtsShift = Math.max(Math.min(ptsDtsShift, sample.pts - sample.dts), -1 * PTS_DTS_SHIFT_TOLERANCE_90KHZ);
}
if (sample.dts < inputSamples[i > 0 ? i - 1 : i].dts) {
sortSamples = true;
}
}
// sort video samples by DTS then PTS then demux id order
if (sortSamples) {
inputSamples.sort(function (a, b) {
const deltadts = a.dts - b.dts;
const deltapts = a.pts - b.pts;
return deltadts || (deltapts || (a.id - b.id));
});
}
// Get first/last DTS
firstDTS = inputSamples[0].dts;
lastDTS = inputSamples[nbSamples - 1].dts;
// on Safari let's signal the same sample duration for all samples
// sample duration (as expected by trun MP4 boxes), should be the delta between sample DTS
// set this constant duration as being the avg delta between consecutive DTS.
const averageSampleDuration = Math.round((lastDTS - firstDTS) / (nbSamples - 1));
// handle broken streams with PTS < DTS, tolerance up 0.2 seconds
if (ptsDtsShift < 0) {
if (ptsDtsShift < averageSampleDuration * -2) {
// Fix for "CNN special report, with CC" in test-streams (including Safari browser)
// With large PTS < DTS errors such as this, we want to correct CTS while maintaining increasing DTS values
logger.warn(`PTS < DTS detected in video samples, offsetting DTS from PTS by ${toMsFromMpegTsClock(-averageSampleDuration, true)} ms`);
let lastDts = ptsDtsShift;
for (let i = 0; i < nbSamples; i++) {
inputSamples[i].dts = lastDts = Math.max(lastDts, inputSamples[i].pts - averageSampleDuration);
inputSamples[i].pts = Math.max(lastDts, inputSamples[i].pts);
}
} else {
// Fix for "Custom IV with bad PTS DTS" in test-streams
// With smaller PTS < DTS errors we can simply move all DTS back. This increases CTS without causing buffer gaps or decode errors in Safari
logger.warn(`PTS < DTS detected in video samples, shifting DTS by ${toMsFromMpegTsClock(ptsDtsShift, true)} ms to overcome this issue`);
for (let i = 0; i < nbSamples; i++) {
inputSamples[i].dts = inputSamples[i].dts + ptsDtsShift;
}
}
firstDTS = inputSamples[0].dts;
lastDTS = inputSamples[nbSamples - 1].dts;
}
// if fragment are contiguous, detect hole/overlapping between fragments
if (contiguous) {
// check timestamp continuity across consecutive fragments (this is to remove inter-fragment gap/hole)
const delta = firstDTS - nextAvcDts;
const foundHole = delta > averageSampleDuration;
const foundOverlap = delta < -1;
if (foundHole || foundOverlap) {
if (foundHole) {
logger.warn(`AVC: ${toMsFromMpegTsClock(delta, true)} ms (${delta}dts) hole between fragments detected, filling it`);
} else {
logger.warn(`AVC: ${toMsFromMpegTsClock(-delta, true)} ms (${delta}dts) overlapping between fragments detected`);
}
firstDTS = nextAvcDts;
const firstPTS = inputSamples[0].pts - delta;
inputSamples[0].dts = firstDTS;
inputSamples[0].pts = firstPTS;
logger.log(`Video: First PTS/DTS adjusted: ${toMsFromMpegTsClock(firstPTS, true)}/${toMsFromMpegTsClock(firstDTS, true)}, delta: ${toMsFromMpegTsClock(delta, true)} ms`);
}
}
if (chromeVersion && chromeVersion < 75) {
firstDTS = Math.max(0, firstDTS);
}
let nbNalu = 0;
let naluLen = 0;
for (let i = 0; i < nbSamples; i++) {
// compute total/avc sample length and nb of NAL units
const sample = inputSamples[i];
const units = sample.units;
const nbUnits = units.length;
let sampleLen = 0;
for (let j = 0; j < nbUnits; j++) {
sampleLen += units[j].data.length;
}
naluLen += sampleLen;
nbNalu += nbUnits;
sample.length = sampleLen;
// normalize PTS/DTS
// ensure sample monotonic DTS
sample.dts = Math.max(sample.dts, firstDTS);
// ensure that computed value is greater or equal than sample DTS
sample.pts = Math.max(sample.pts, sample.dts, 0);
minPTS = Math.min(sample.pts, minPTS);
maxPTS = Math.max(sample.pts, maxPTS);
}
lastDTS = inputSamples[nbSamples - 1].dts;
/* concatenate the video data and construct the mdat in place
(need 8 more bytes to fill length and mpdat type) */
let mdatSize = naluLen + (4 * nbNalu) + 8;
try {
mdat = new Uint8Array(mdatSize);
} catch (err) {
this.observer.trigger(Event.ERROR, { type: ErrorTypes.MUX_ERROR, details: ErrorDetails.REMUX_ALLOC_ERROR, fatal: false, bytes: mdatSize, reason: `fail allocating video mdat ${mdatSize}` });
return;
}
let view = new DataView(mdat.buffer);
view.setUint32(0, mdatSize);
mdat.set(MP4.types.mdat, 4);
for (let i = 0; i < nbSamples; i++) {
const avcSample = inputSamples[i];
const avcSampleUnits = avcSample.units;
let mp4SampleLength = 0;
let compositionTimeOffset;
// convert NALU bitstream to MP4 format (prepend NALU with size field)
for (let j = 0, nbUnits = avcSampleUnits.length; j < nbUnits; j++) {
const unit = avcSampleUnits[j];
const unitData = unit.data;
const unitDataLen = unit.data.byteLength;
view.setUint32(offset, unitDataLen);
offset += 4;
mdat.set(unitData, offset);
offset += unitDataLen;
mp4SampleLength += 4 + unitDataLen;
}
// expected sample duration is the Decoding Timestamp diff of consecutive samples
if (i < nbSamples - 1) {
mp4SampleDuration = inputSamples[i + 1].dts - avcSample.dts;
} else {
const config = this.config;
const lastFrameDuration = avcSample.dts - inputSamples[i > 0 ? i - 1 : i].dts;
if (config.stretchShortVideoTrack) {
// In some cases, a segment's audio track duration may exceed the video track duration.
// Since we've already remuxed audio, and we know how long the audio track is, we look to
// see if the delta to the next segment is longer than maxBufferHole.
// If so, playback would potentially get stuck, so we artificially inflate
// the duration of the last frame to minimize any potential gap between segments.
const maxBufferHole = config.maxBufferHole;
const gapTolerance = Math.floor(maxBufferHole * timeScale);
const deltaToFrameEnd = (audioTrackLength ? minPTS + audioTrackLength * timeScale : this.nextAudioPts) - avcSample.pts;
if (deltaToFrameEnd > gapTolerance) {
// We subtract lastFrameDuration from deltaToFrameEnd to try to prevent any video
// frame overlap. maxBufferHole should be >> lastFrameDuration anyway.
mp4SampleDuration = deltaToFrameEnd - lastFrameDuration;
if (mp4SampleDuration < 0) {
mp4SampleDuration = lastFrameDuration;
}
logger.log(`It is approximately ${toMsFromMpegTsClock(deltaToFrameEnd, false)} ms to the next segment; using duration ${toMsFromMpegTsClock(mp4SampleDuration, false)} ms for the last video frame.`);
} else {
mp4SampleDuration = lastFrameDuration;
}
} else {
mp4SampleDuration = lastFrameDuration;
}
}
compositionTimeOffset = Math.round(avcSample.pts - avcSample.dts);
// console.log('PTS/DTS/initDTS/normPTS/normDTS/relative PTS : ${avcSample.pts}/${avcSample.dts}/${initDTS}/${ptsnorm}/${dtsnorm}/${(avcSample.pts/4294967296).toFixed(3)}');
outputSamples.push({
size: mp4SampleLength,
// constant duration
duration: mp4SampleDuration,
cts: compositionTimeOffset,
flags: {
isLeading: 0,
isDependedOn: 0,
hasRedundancy: 0,
degradPrio: 0,
dependsOn: avcSample.key ? 2 : 1,
isNonSync: avcSample.key ? 0 : 1
}
});
}
// next AVC sample DTS should be equal to last sample DTS + last sample duration (in PES timescale)
this.nextAvcDts = lastDTS + mp4SampleDuration;
const dropped = track.dropped;
track.nbNalu = 0;
track.dropped = 0;
if (outputSamples.length && chromeVersion && chromeVersion < 70) {
const flags = outputSamples[0].flags;
// chrome workaround, mark first sample as being a Random Access Point to avoid sourcebuffer append issue
// https://code.google.com/p/chromium/issues/detail?id=229412
flags.dependsOn = 2;
flags.isNonSync = 0;
}
track.samples = outputSamples;
moof = MP4.moof(track.sequenceNumber++, firstDTS, track);
track.samples = [];
const data = {
data1: moof,
data2: mdat,
startPTS: minPTS / timeScale,
endPTS: (maxPTS + mp4SampleDuration) / timeScale,
startDTS: firstDTS / timeScale,
endDTS: this.nextAvcDts / timeScale,
type: 'video',
hasAudio: false,
hasVideo: true,
nb: outputSamples.length,
dropped: dropped
};
this.observer.trigger(Event.FRAG_PARSING_DATA, data);
return data;
}
remuxAudio (track, timeOffset, contiguous, accurateTimeOffset, videoTimeOffset) {
const inputTimeScale = track.inputTimeScale;
const mp4timeScale = track.timescale;
const scaleFactor = inputTimeScale / mp4timeScale;
const mp4SampleDuration = track.isAAC ? 1024 : 1152;
const inputSampleDuration = mp4SampleDuration * scaleFactor;
const initPTS = this._initPTS;
const rawMPEG = !track.isAAC && this.typeSupported.mpeg;
let mp4Sample;
let fillFrame;
let mdat;
let moof;
let firstPTS;
let lastPTS;
let offset = (rawMPEG ? 0 : 8);
let inputSamples = track.samples;
let outputSamples = [];
let nextAudioPts = this.nextAudioPts;
// for audio samples, also consider consecutive fragments as being contiguous (even if a level switch occurs),
// for sake of clarity:
// consecutive fragments are frags with
// - less than 100ms gaps between new time offset (if accurate) and next expected PTS OR
// - less than 20 audio frames distance
// contiguous fragments are consecutive fragments from same quality level (same level, new SN = old SN + 1)
// this helps ensuring audio continuity
// and this also avoids audio glitches/cut when switching quality, or reporting wrong duration on first audio frame
contiguous |= (inputSamples.length && nextAudioPts &&
((accurateTimeOffset && Math.abs(timeOffset - nextAudioPts / inputTimeScale) < 0.1) ||
Math.abs((inputSamples[0].pts - nextAudioPts - initPTS)) < 20 * inputSampleDuration)
);
// compute normalized PTS
inputSamples.forEach(function (sample) {
sample.pts = sample.dts = PTSNormalize(sample.pts - initPTS, timeOffset * inputTimeScale);
});
// filter out sample with negative PTS that are not playable anyway
// if we don't remove these negative samples, they will shift all audio samples forward.
// leading to audio overlap between current / next fragment
inputSamples = inputSamples.filter((sample) => sample.pts >= 0);
// in case all samples have negative PTS, and have been filtered out, return now
if (inputSamples.length === 0) {
return;
}
if (!contiguous) {
if (videoTimeOffset === 0) {
// Set the start to 0 to match video so that start gaps larger than inputSampleDuration are filled with silence
nextAudioPts = 0;
} else if (accurateTimeOffset) {
// When not seeking, not live, and LevelDetails.PTSKnown, use fragment start as predicted next audio PTS
nextAudioPts = Math.max(0, timeOffset * inputTimeScale);
} else {
// if frags are not contiguous and if we cant trust time offset, let's use first sample PTS as next audio PTS
nextAudioPts = inputSamples[0].pts;
}
}
// If the audio track is missing samples, the frames seem to get "left-shifted" within the
// resulting mp4 segment, causing sync issues and leaving gaps at the end of the audio segment.
// In an effort to prevent this from happening, we inject frames here where there are gaps.
// When possible, we inject a silent frame; when that's not possible, we duplicate the last
// frame.
if (track.isAAC) {
const maxAudioFramesDrift = this.config.maxAudioFramesDrift;
for (let i = 0, nextPts = nextAudioPts; i < inputSamples.length;) {
// First, let's see how far off this frame is from where we expect it to be
const sample = inputSamples[i];
let pts = sample.pts;
let delta = pts - nextPts;
// If we're overlapping by more than a duration, drop this sample
if (delta <= -maxAudioFramesDrift * inputSampleDuration) {
if (contiguous || i > 0) {
logger.warn(`Dropping 1 audio frame @ ${toMsFromMpegTsClock(nextPts, true) / 1000}s due to ${toMsFromMpegTsClock(delta, true)} ms overlap.`);
inputSamples.splice(i, 1);
// Don't touch nextPtsNorm or i
} else {
// When changing qualities we can't trust that audio has been appended up to nextAudioPts
// Warn about the overlap but do not drop samples as that can introduce buffer gaps
logger.warn(`Audio frame @ ${toMsFromMpegTsClock(pts, true) / 1000}s overlaps nextAudioPts by ${toMsFromMpegTsClock(delta, true)} ms.`);
nextPts = pts + inputSampleDuration;
i++;
}
} // eslint-disable-line brace-style
// Insert missing frames if:
// 1: We're more than maxAudioFramesDrift frame away
// 2: Not more than MAX_SILENT_FRAME_DURATION away
else if (delta >= maxAudioFramesDrift * inputSampleDuration && delta < MAX_SILENT_FRAME_DURATION_90KHZ) {
const missing = Math.floor(delta / inputSampleDuration);
// Adjust nextPts so that silent samples are aligned with media pts. This will prevent media samples from
// later being shifted if nextPts is based on timeOffset and delta is not a multiple of inputSampleDuration.
nextPts = pts - missing * inputSampleDuration;
logger.warn(`Injecting ${missing} audio frames @ ${toMsFromMpegTsClock(nextPts, true) / 1000}s due to ${toMsFromMpegTsClock(delta, true)} ms gap.`);
for (let j = 0; j < missing; j++) {
let newStamp = Math.max(nextPts, 0);
fillFrame = AAC.getSilentFrame(track.manifestCodec || track.codec, track.channelCount);
if (!fillFrame) {
logger.log('Unable to get silent frame for given audio codec; duplicating last frame instead.');
fillFrame = sample.unit.subarray();
}
inputSamples.splice(i, 0, { unit: fillFrame, pts: newStamp, dts: newStamp });
nextPts += inputSampleDuration;
i++;
}
// Adjust sample to next expected pts
sample.pts = sample.dts = nextPts;
nextPts += inputSampleDuration;
i++;
} else {
// Otherwise, just adjust pts
if (Math.abs(delta) > (0.1 * inputSampleDuration)) {
// logger.log(`Invalid frame delta ${Math.round(delta + inputSampleDuration)} at PTS ${Math.round(pts / 90)} (should be ${Math.round(inputSampleDuration)}).`);
}
sample.pts = sample.dts = nextPts;
nextPts += inputSampleDuration;
i++;
}
}
}
// compute mdat size, as we eventually filtered/added some samples
let nbSamples = inputSamples.length;
let mdatSize = 0;
while (nbSamples--) {
mdatSize += inputSamples[nbSamples].unit.byteLength;
}
for (let j = 0, nbSamples = inputSamples.length; j < nbSamples; j++) {
let audioSample = inputSamples[j];
let unit = audioSample.unit;
let pts = audioSample.pts;
// logger.log(`Audio/PTS:${toMsFromMpegTsClock(pts, true)}`);
// if not first sample
if (lastPTS !== undefined && mp4Sample) {
mp4Sample.duration = Math.round((pts - lastPTS) / scaleFactor);
} else {
let delta = pts - nextAudioPts;
let numMissingFrames = 0;
// if fragment are contiguous, detect hole/overlapping between fragments
// contiguous fragments are consecutive fragments from same quality level (same level, new SN = old SN + 1)
if (contiguous && track.isAAC) {
// log delta
if (delta) {
if (delta > 0 && delta < MAX_SILENT_FRAME_DURATION_90KHZ) {
// Q: why do we have to round here, shouldn't this always result in an integer if timestamps are correct,
// and if not, shouldn't we actually Math.ceil() instead?
numMissingFrames = Math.round((pts - nextAudioPts) / inputSampleDuration);
logger.log(`${toMsFromMpegTsClock(delta, true)} ms hole between AAC samples detected,filling it`);
if (numMissingFrames > 0) {
fillFrame = AAC.getSilentFrame(track.manifestCodec || track.codec, track.channelCount);
if (!fillFrame) {
fillFrame = unit.subarray();
}
mdatSize += numMissingFrames * fillFrame.length;
}
// if we have frame overlap, overlapping for more than half a frame duraion
} else if (delta < -12) {
// drop overlapping audio frames... browser will deal with it
logger.log(`drop overlapping AAC sample, expected/parsed/delta: ${toMsFromMpegTsClock(nextAudioPts, true)} ms / ${toMsFromMpegTsClock(pts, true)} ms / ${toMsFromMpegTsClock(-delta, true)} ms`);
mdatSize -= unit.byteLength;
continue;
}
// set PTS/DTS to expected PTS/DTS
pts = nextAudioPts;
}
}
// remember first PTS of our audioSamples
firstPTS = pts;
if (mdatSize > 0) {
mdatSize += offset;
try {
mdat = new Uint8Array(mdatSize);
} catch (err) {
this.observer.trigger(Event.ERROR, { type: ErrorTypes.MUX_ERROR, details: ErrorDetails.REMUX_ALLOC_ERROR, fatal: false, bytes: mdatSize, reason: `fail allocating audio mdat ${mdatSize}` });
return;
}
if (!rawMPEG) {
const view = new DataView(mdat.buffer);
view.setUint32(0, mdatSize);
mdat.set(MP4.types.mdat, 4);
}
} else {
// no audio samples
return;
}
for (let i = 0; i < numMissingFrames; i++) {
fillFrame = AAC.getSilentFrame(track.manifestCodec || track.codec, track.channelCount);
if (!fillFrame) {
logger.log('Unable to get silent frame for given audio codec; duplicating this frame instead.');
fillFrame = unit.subarray();
}
mdat.set(fillFrame, offset);
offset += fillFrame.byteLength;
mp4Sample = {
size: fillFrame.byteLength,
cts: 0,
duration: 1024,
flags: {
isLeading: 0,
isDependedOn: 0,
hasRedundancy: 0,
degradPrio: 0,
dependsOn: 1
}
};
outputSamples.push(mp4Sample);
}
}
mdat.set(unit, offset);
let unitLen = unit.byteLength;
offset += unitLen;
// console.log('PTS/DTS/initDTS/normPTS/normDTS/relative PTS : ${audioSample.pts}/${audioSample.dts}/${initDTS}/${ptsnorm}/${dtsnorm}/${(audioSample.pts/4294967296).toFixed(3)}');
mp4Sample = {
size: unitLen,
cts: 0,
duration: 0,
flags: {
isLeading: 0,
isDependedOn: 0,
hasRedundancy: 0,
degradPrio: 0,
dependsOn: 1
}
};
outputSamples.push(mp4Sample);
lastPTS = pts;
}
let lastSampleDuration = 0;
nbSamples = outputSamples.length;
// set last sample duration as being identical to previous sample
if (nbSamples >= 2) {
lastSampleDuration = outputSamples[nbSamples - 2].duration;
mp4Sample.duration = lastSampleDuration;
}
if (nbSamples) {
// next audio sample PTS should be equal to last sample PTS + duration
this.nextAudioPts = nextAudioPts = lastPTS + scaleFactor * lastSampleDuration;
// logger.log('Audio/PTS/PTSend:' + audioSample.pts.toFixed(0) + '/' + this.nextAacDts.toFixed(0));
track.samples = outputSamples;
if (rawMPEG) {
moof = new Uint8Array();
} else {
moof = MP4.moof(track.sequenceNumber++, firstPTS / scaleFactor, track);
}
track.samples = [];
const start = firstPTS / inputTimeScale;
const end = nextAudioPts / inputTimeScale;
const audioData = {
data1: moof,
data2: mdat,
startPTS: start,
endPTS: end,
startDTS: start,
endDTS: end,
type: 'audio',
hasAudio: true,
hasVideo: false,
nb: nbSamples
};
this.observer.trigger(Event.FRAG_PARSING_DATA, audioData);
return audioData;
}
return null;
}
remuxEmptyAudio (track, timeOffset, contiguous, videoData) {
let inputTimeScale = track.inputTimeScale;
let mp4timeScale = track.samplerate ? track.samplerate : inputTimeScale;
let scaleFactor = inputTimeScale / mp4timeScale;
let nextAudioPts = this.nextAudioPts;
// sync with video's timestamp
let startDTS = (nextAudioPts !== undefined ? nextAudioPts : videoData.startDTS * inputTimeScale) + this._initDTS;
let endDTS = videoData.endDTS * inputTimeScale + this._initDTS;
// one sample's duration value
let sampleDuration = 1024;
let frameDuration = scaleFactor * sampleDuration;
// samples count of this segment's duration
let nbSamples = Math.ceil((endDTS - startDTS) / frameDuration);
// silent frame
let silentFrame = AAC.getSilentFrame(track.manifestCodec || track.codec, track.channelCount);
logger.warn('remux empty Audio');
// Can't remux if we can't generate a silent frame...
if (!silentFrame) {
logger.trace('Unable to remuxEmptyAudio since we were unable to get a silent frame for given audio codec!');
return;
}
let samples = [];
for (let i = 0; i < nbSamples; i++) {
let stamp = startDTS + i * frameDuration;
samples.push({ unit: silentFrame, pts: stamp, dts: stamp });
}
track.samples = samples;
this.remuxAudio(track, timeOffset, contiguous);
}
remuxID3 (track, timeOffset) {
const length = track.samples.length;
if (!length) {
return;
}
const inputTimeScale = track.inputTimeScale;
const initPTS = this._initPTS;
const initDTS = this._initDTS;
// consume samples
for (let index = 0; index < length; index++) {
const sample = track.samples[index];
// setting id3 pts, dts to relative time
// using this._initPTS and this._initDTS to calculate relative time
sample.pts = PTSNormalize(sample.pts - initPTS, timeOffset * inputTimeScale) / inputTimeScale;
sample.dts = PTSNormalize(sample.dts - initDTS, timeOffset * inputTimeScale) / inputTimeScale;
}
this.observer.trigger(Event.FRAG_PARSING_METADATA, {
samples: track.samples
});
track.samples = [];
}
remuxText (track, timeOffset) {
const length = track.samples.length;
const inputTimeScale = track.inputTimeScale;
const initPTS = this._initPTS;
// consume samples
if (length) {
for (let index = 0; index < length; index++) {
const sample = track.samples[index];
// setting text pts, dts to relative time
// using this._initPTS and this._initDTS to calculate relative time
sample.pts = PTSNormalize(sample.pts - initPTS, timeOffset * inputTimeScale) / inputTimeScale;
}
track.samples.sort(function (a, b) {
return (a.pts - b.pts);
});
this.observer.trigger(Event.FRAG_PARSING_USERDATA, {
samples: track.samples
});
}
track.samples = [];
}
}
function PTSNormalize (value, reference) {
let offset;
if (reference === undefined) {
return value;
}
if (reference < value) {
// - 2^33
offset = -8589934592;
} else {
// + 2^33
offset = 8589934592;
}
/* PTS is 33bit (from 0 to 2^33 -1)
if diff between value and reference is bigger than half of the amplitude (2^32) then it means that
PTS looping occured. fill the gap */
while (Math.abs(value - reference) > 4294967296) {
value += offset;
}
return value;
}
export default MP4Remuxer;
