mediabunny
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Pure TypeScript media toolkit for reading, writing, and converting media files, directly in the browser.
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JavaScript
/*!
* Copyright (c) 2025-present, Vanilagy and contributors
*
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at https://mozilla.org/MPL/2.0/.
*/
import { Bitstream, COLOR_PRIMARIES_MAP, MATRIX_COEFFICIENTS_MAP, TRANSFER_CHARACTERISTICS_MAP, UNDETERMINED_LANGUAGE, assert, colorSpaceIsComplete, normalizeRotation, promiseWithResolvers, roundToMultiple, textEncoder, toUint8Array, writeBits, } from '../misc.js';
import { CODEC_STRING_MAP, EBMLFloat32, EBMLFloat64, EBMLId, EBMLSignedInt, EBMLWriter, } from './ebml.js';
import { buildMatroskaMimeType } from './matroska-misc.js';
import { WebMOutputFormat } from '../output-format.js';
import { formatSubtitleTimestamp, inlineTimestampRegex, parseSubtitleTimestamp, } from '../subtitles.js';
import { OPUS_INTERNAL_SAMPLE_RATE, PCM_AUDIO_CODECS, generateAv1CodecConfigurationFromCodecString, generateVp9CodecConfigurationFromCodecString, parsePcmCodec, validateAudioChunkMetadata, validateSubtitleMetadata, validateVideoChunkMetadata, } from '../codec.js';
import { Muxer } from '../muxer.js';
import { parseOpusIdentificationHeader } from '../codec-data.js';
const MIN_CLUSTER_TIMESTAMP_MS = -(2 ** 15);
const MAX_CLUSTER_TIMESTAMP_MS = 2 ** 15 - 1;
const APP_NAME = 'https://github.com/Vanilagy/mediabunny';
const SEGMENT_SIZE_BYTES = 6;
const CLUSTER_SIZE_BYTES = 5;
const TRACK_TYPE_MAP = {
video: 1,
audio: 2,
subtitle: 17,
};
export class MatroskaMuxer extends Muxer {
constructor(output, format) {
super(output);
this.trackDatas = [];
this.allTracksKnown = promiseWithResolvers();
this.segment = null;
this.segmentInfo = null;
this.seekHead = null;
this.tracksElement = null;
this.segmentDuration = null;
this.cues = null;
this.currentCluster = null;
this.currentClusterStartMsTimestamp = null;
this.currentClusterMaxMsTimestamp = null;
this.trackDatasInCurrentCluster = new Map();
this.duration = 0;
this.writer = output._writer;
this.format = format;
this.ebmlWriter = new EBMLWriter(this.writer);
if (this.format._options.appendOnly) {
this.writer.ensureMonotonicity = true;
}
}
async start() {
const release = await this.mutex.acquire();
this.writeEBMLHeader();
if (!this.format._options.appendOnly) {
this.createSeekHead();
}
this.createSegmentInfo();
this.createCues();
await this.writer.flush();
release();
}
writeEBMLHeader() {
if (this.format._options.onEbmlHeader) {
this.writer.startTrackingWrites();
}
const ebmlHeader = { id: EBMLId.EBML, data: [
{ id: EBMLId.EBMLVersion, data: 1 },
{ id: EBMLId.EBMLReadVersion, data: 1 },
{ id: EBMLId.EBMLMaxIDLength, data: 4 },
{ id: EBMLId.EBMLMaxSizeLength, data: 8 },
{ id: EBMLId.DocType, data: this.format instanceof WebMOutputFormat ? 'webm' : 'matroska' },
{ id: EBMLId.DocTypeVersion, data: 2 },
{ id: EBMLId.DocTypeReadVersion, data: 2 },
] };
this.ebmlWriter.writeEBML(ebmlHeader);
if (this.format._options.onEbmlHeader) {
const { data, start } = this.writer.stopTrackingWrites(); // start should be 0
this.format._options.onEbmlHeader(data, start);
}
}
/**
* Creates a SeekHead element which is positioned near the start of the file and allows the media player to seek to
* relevant sections more easily. Since we don't know the positions of those sections yet, we'll set them later.
*/
createSeekHead() {
const kaxCues = new Uint8Array([0x1c, 0x53, 0xbb, 0x6b]);
const kaxInfo = new Uint8Array([0x15, 0x49, 0xa9, 0x66]);
const kaxTracks = new Uint8Array([0x16, 0x54, 0xae, 0x6b]);
const seekHead = { id: EBMLId.SeekHead, data: [
{ id: EBMLId.Seek, data: [
{ id: EBMLId.SeekID, data: kaxCues },
{ id: EBMLId.SeekPosition, size: 5, data: 0 },
] },
{ id: EBMLId.Seek, data: [
{ id: EBMLId.SeekID, data: kaxInfo },
{ id: EBMLId.SeekPosition, size: 5, data: 0 },
] },
{ id: EBMLId.Seek, data: [
{ id: EBMLId.SeekID, data: kaxTracks },
{ id: EBMLId.SeekPosition, size: 5, data: 0 },
] },
] };
this.seekHead = seekHead;
}
createSegmentInfo() {
const segmentDuration = { id: EBMLId.Duration, data: new EBMLFloat64(0) };
this.segmentDuration = segmentDuration;
const segmentInfo = { id: EBMLId.Info, data: [
{ id: EBMLId.TimestampScale, data: 1e6 },
{ id: EBMLId.MuxingApp, data: APP_NAME },
{ id: EBMLId.WritingApp, data: APP_NAME },
!this.format._options.appendOnly ? segmentDuration : null,
] };
this.segmentInfo = segmentInfo;
}
createTracks() {
const tracksElement = { id: EBMLId.Tracks, data: [] };
this.tracksElement = tracksElement;
for (const trackData of this.trackDatas) {
const codecId = CODEC_STRING_MAP[trackData.track.source._codec];
assert(codecId);
let seekPreRollNs = 0;
if (trackData.type === 'audio' && trackData.track.source._codec === 'opus') {
seekPreRollNs = 1e6 * 80; // In "Matroska ticks" (nanoseconds)
const description = trackData.info.decoderConfig.description;
if (description) {
const bytes = toUint8Array(description);
const header = parseOpusIdentificationHeader(bytes);
// Use the preSkip value from the header
seekPreRollNs = Math.round(1e9 * (header.preSkip / OPUS_INTERNAL_SAMPLE_RATE));
}
}
tracksElement.data.push({ id: EBMLId.TrackEntry, data: [
{ id: EBMLId.TrackNumber, data: trackData.track.id },
{ id: EBMLId.TrackUID, data: trackData.track.id },
{ id: EBMLId.TrackType, data: TRACK_TYPE_MAP[trackData.type] },
{ id: EBMLId.FlagLacing, data: 0 },
{ id: EBMLId.Language, data: trackData.track.metadata.languageCode ?? UNDETERMINED_LANGUAGE },
{ id: EBMLId.CodecID, data: codecId },
{ id: EBMLId.CodecDelay, data: 0 },
{ id: EBMLId.SeekPreRoll, data: seekPreRollNs },
(trackData.type === 'video' ? this.videoSpecificTrackInfo(trackData) : null),
(trackData.type === 'audio' ? this.audioSpecificTrackInfo(trackData) : null),
(trackData.type === 'subtitle' ? this.subtitleSpecificTrackInfo(trackData) : null),
] });
}
}
videoSpecificTrackInfo(trackData) {
const { frameRate, rotation } = trackData.track.metadata;
const elements = [
(trackData.info.decoderConfig.description
? {
id: EBMLId.CodecPrivate,
data: toUint8Array(trackData.info.decoderConfig.description),
}
: null),
(frameRate
? {
id: EBMLId.DefaultDuration,
data: 1e9 / frameRate,
}
: null),
];
// Convert from clockwise to counter-clockwise
const flippedRotation = rotation ? normalizeRotation(-rotation) : 0;
const colorSpace = trackData.info.decoderConfig.colorSpace;
const videoElement = { id: EBMLId.Video, data: [
{ id: EBMLId.PixelWidth, data: trackData.info.width },
{ id: EBMLId.PixelHeight, data: trackData.info.height },
(colorSpaceIsComplete(colorSpace)
? {
id: EBMLId.Colour,
data: [
{
id: EBMLId.MatrixCoefficients,
data: MATRIX_COEFFICIENTS_MAP[colorSpace.matrix],
},
{
id: EBMLId.TransferCharacteristics,
data: TRANSFER_CHARACTERISTICS_MAP[colorSpace.transfer],
},
{
id: EBMLId.Primaries,
data: COLOR_PRIMARIES_MAP[colorSpace.primaries],
},
{
id: EBMLId.Range,
data: colorSpace.fullRange ? 2 : 1,
},
],
}
: null),
(flippedRotation
? {
id: EBMLId.Projection,
data: [
{
id: EBMLId.ProjectionType,
data: 0, // rectangular
},
{
id: EBMLId.ProjectionPoseRoll,
data: new EBMLFloat32((flippedRotation + 180) % 360 - 180), // [0, 270] -> [-180, 90]
},
],
}
: null),
] };
elements.push(videoElement);
return elements;
}
audioSpecificTrackInfo(trackData) {
const pcmInfo = PCM_AUDIO_CODECS.includes(trackData.track.source._codec)
? parsePcmCodec(trackData.track.source._codec)
: null;
return [
(trackData.info.decoderConfig.description
? {
id: EBMLId.CodecPrivate,
data: toUint8Array(trackData.info.decoderConfig.description),
}
: null),
{ id: EBMLId.Audio, data: [
{ id: EBMLId.SamplingFrequency, data: new EBMLFloat32(trackData.info.sampleRate) },
{ id: EBMLId.Channels, data: trackData.info.numberOfChannels },
pcmInfo ? { id: EBMLId.BitDepth, data: 8 * pcmInfo.sampleSize } : null,
] },
];
}
subtitleSpecificTrackInfo(trackData) {
return [
{ id: EBMLId.CodecPrivate, data: textEncoder.encode(trackData.info.config.description) },
];
}
createSegment() {
const segment = {
id: EBMLId.Segment,
size: this.format._options.appendOnly ? -1 : SEGMENT_SIZE_BYTES,
data: [
!this.format._options.appendOnly ? this.seekHead : null,
this.segmentInfo,
this.tracksElement,
],
};
this.segment = segment;
if (this.format._options.onSegmentHeader) {
this.writer.startTrackingWrites();
}
this.ebmlWriter.writeEBML(segment);
if (this.format._options.onSegmentHeader) {
const { data, start } = this.writer.stopTrackingWrites();
this.format._options.onSegmentHeader(data, start);
}
}
createCues() {
this.cues = { id: EBMLId.Cues, data: [] };
}
get segmentDataOffset() {
assert(this.segment);
return this.ebmlWriter.dataOffsets.get(this.segment);
}
allTracksAreKnown() {
for (const track of this.output._tracks) {
if (!track.source._closed && !this.trackDatas.some(x => x.track === track)) {
return false; // We haven't seen a sample from this open track yet
}
}
return true;
}
async getMimeType() {
await this.allTracksKnown.promise;
const codecStrings = this.trackDatas.map((trackData) => {
if (trackData.type === 'video') {
return trackData.info.decoderConfig.codec;
}
else if (trackData.type === 'audio') {
return trackData.info.decoderConfig.codec;
}
else {
const map = {
webvtt: 'wvtt',
};
return map[trackData.track.source._codec];
}
});
return buildMatroskaMimeType({
isWebM: this.format instanceof WebMOutputFormat,
hasVideo: this.trackDatas.some(x => x.type === 'video'),
hasAudio: this.trackDatas.some(x => x.type === 'audio'),
codecStrings,
});
}
getVideoTrackData(track, meta) {
const existingTrackData = this.trackDatas.find(x => x.track === track);
if (existingTrackData) {
return existingTrackData;
}
validateVideoChunkMetadata(meta);
assert(meta);
assert(meta.decoderConfig);
assert(meta.decoderConfig.codedWidth !== undefined);
assert(meta.decoderConfig.codedHeight !== undefined);
const newTrackData = {
track,
type: 'video',
info: {
width: meta.decoderConfig.codedWidth,
height: meta.decoderConfig.codedHeight,
decoderConfig: meta.decoderConfig,
},
chunkQueue: [],
lastWrittenMsTimestamp: null,
};
if (track.source._codec === 'vp9') {
// https://www.webmproject.org/docs/container specifies that VP9 "SHOULD" make use of the CodecPrivate
// field. Since WebCodecs makes no use of the description field for VP9, we need to derive it ourselves:
newTrackData.info.decoderConfig = {
...newTrackData.info.decoderConfig,
description: new Uint8Array(generateVp9CodecConfigurationFromCodecString(newTrackData.info.decoderConfig.codec)),
};
}
else if (track.source._codec === 'av1') {
// Per https://github.com/ietf-wg-cellar/matroska-specification/blob/master/codec/av1.md, AV1 requires
// CodecPrivate to be set, but WebCodecs makes no use of the description field for AV1. Thus, let's derive
// it ourselves:
newTrackData.info.decoderConfig = {
...newTrackData.info.decoderConfig,
description: new Uint8Array(generateAv1CodecConfigurationFromCodecString(newTrackData.info.decoderConfig.codec)),
};
}
this.trackDatas.push(newTrackData);
this.trackDatas.sort((a, b) => a.track.id - b.track.id);
if (this.allTracksAreKnown()) {
this.allTracksKnown.resolve();
}
return newTrackData;
}
getAudioTrackData(track, meta) {
const existingTrackData = this.trackDatas.find(x => x.track === track);
if (existingTrackData) {
return existingTrackData;
}
validateAudioChunkMetadata(meta);
assert(meta);
assert(meta.decoderConfig);
const newTrackData = {
track,
type: 'audio',
info: {
numberOfChannels: meta.decoderConfig.numberOfChannels,
sampleRate: meta.decoderConfig.sampleRate,
decoderConfig: meta.decoderConfig,
},
chunkQueue: [],
lastWrittenMsTimestamp: null,
};
this.trackDatas.push(newTrackData);
this.trackDatas.sort((a, b) => a.track.id - b.track.id);
if (this.allTracksAreKnown()) {
this.allTracksKnown.resolve();
}
return newTrackData;
}
getSubtitleTrackData(track, meta) {
const existingTrackData = this.trackDatas.find(x => x.track === track);
if (existingTrackData) {
return existingTrackData;
}
validateSubtitleMetadata(meta);
assert(meta);
assert(meta.config);
const newTrackData = {
track,
type: 'subtitle',
info: {
config: meta.config,
},
chunkQueue: [],
lastWrittenMsTimestamp: null,
};
this.trackDatas.push(newTrackData);
this.trackDatas.sort((a, b) => a.track.id - b.track.id);
if (this.allTracksAreKnown()) {
this.allTracksKnown.resolve();
}
return newTrackData;
}
async addEncodedVideoPacket(track, packet, meta) {
const release = await this.mutex.acquire();
try {
const trackData = this.getVideoTrackData(track, meta);
const isKeyFrame = packet.type === 'key';
let timestamp = this.validateAndNormalizeTimestamp(trackData.track, packet.timestamp, isKeyFrame);
let duration = packet.duration;
if (track.metadata.frameRate !== undefined) {
// Constrain the time values to the frame rate
timestamp = roundToMultiple(timestamp, 1 / track.metadata.frameRate);
duration = roundToMultiple(duration, 1 / track.metadata.frameRate);
}
const videoChunk = this.createInternalChunk(packet.data, timestamp, duration, packet.type);
if (track.source._codec === 'vp9')
this.fixVP9ColorSpace(trackData, videoChunk);
trackData.chunkQueue.push(videoChunk);
await this.interleaveChunks();
}
finally {
release();
}
}
async addEncodedAudioPacket(track, packet, meta) {
const release = await this.mutex.acquire();
try {
const trackData = this.getAudioTrackData(track, meta);
const isKeyFrame = packet.type === 'key';
const timestamp = this.validateAndNormalizeTimestamp(trackData.track, packet.timestamp, isKeyFrame);
const audioChunk = this.createInternalChunk(packet.data, timestamp, packet.duration, packet.type);
trackData.chunkQueue.push(audioChunk);
await this.interleaveChunks();
}
finally {
release();
}
}
async addSubtitleCue(track, cue, meta) {
const release = await this.mutex.acquire();
try {
const trackData = this.getSubtitleTrackData(track, meta);
const timestamp = this.validateAndNormalizeTimestamp(trackData.track, cue.timestamp, true);
let bodyText = cue.text;
const timestampMs = Math.round(timestamp * 1000);
// Replace in-body timestamps so that they're relative to the cue start time
inlineTimestampRegex.lastIndex = 0;
bodyText = bodyText.replace(inlineTimestampRegex, (match) => {
const time = parseSubtitleTimestamp(match.slice(1, -1));
const offsetTime = time - timestampMs;
return `<${formatSubtitleTimestamp(offsetTime)}>`;
});
const body = textEncoder.encode(bodyText);
const additions = `${cue.settings ?? ''}\n${cue.identifier ?? ''}\n${cue.notes ?? ''}`;
const subtitleChunk = this.createInternalChunk(body, timestamp, cue.duration, 'key', additions.trim() ? textEncoder.encode(additions) : null);
trackData.chunkQueue.push(subtitleChunk);
await this.interleaveChunks();
}
finally {
release();
}
}
async interleaveChunks(isFinalCall = false) {
if (!isFinalCall) {
if (!this.allTracksAreKnown()) {
return; // We can't interleave yet as we don't yet know how many tracks we'll truly have
}
}
outer: while (true) {
let trackWithMinTimestamp = null;
let minTimestamp = Infinity;
for (const trackData of this.trackDatas) {
if (!isFinalCall && trackData.chunkQueue.length === 0 && !trackData.track.source._closed) {
break outer;
}
if (trackData.chunkQueue.length > 0 && trackData.chunkQueue[0].timestamp < minTimestamp) {
trackWithMinTimestamp = trackData;
minTimestamp = trackData.chunkQueue[0].timestamp;
}
}
if (!trackWithMinTimestamp) {
break;
}
const chunk = trackWithMinTimestamp.chunkQueue.shift();
this.writeBlock(trackWithMinTimestamp, chunk);
}
if (!isFinalCall) {
await this.writer.flush();
}
}
/**
* Due to [a bug in Chromium](https://bugs.chromium.org/p/chromium/issues/detail?id=1377842), VP9 streams often
* lack color space information. This method patches in that information.
*/
fixVP9ColorSpace(trackData, chunk) {
// http://downloads.webmproject.org/docs/vp9/vp9-bitstream_superframe-and-uncompressed-header_v1.0.pdf
if (chunk.type !== 'key')
return;
if (!trackData.info.decoderConfig.colorSpace || !trackData.info.decoderConfig.colorSpace.matrix)
return;
const bitstream = new Bitstream(chunk.data);
bitstream.skipBits(2);
const profileLowBit = bitstream.readBits(1);
const profileHighBit = bitstream.readBits(1);
const profile = (profileHighBit << 1) + profileLowBit;
if (profile === 3)
bitstream.skipBits(1);
const showExistingFrame = bitstream.readBits(1);
if (showExistingFrame)
return;
const frameType = bitstream.readBits(1);
if (frameType !== 0)
return; // Just to be sure
bitstream.skipBits(2);
const syncCode = bitstream.readBits(24);
if (syncCode !== 0x498342)
return;
if (profile >= 2)
bitstream.skipBits(1);
const colorSpaceID = {
rgb: 7,
bt709: 2,
bt470bg: 1,
smpte170m: 3,
}[trackData.info.decoderConfig.colorSpace.matrix];
// The bitstream position is now at the start of the color space bits.
// We can use the global writeBits function here as requested.
writeBits(chunk.data, bitstream.pos, bitstream.pos + 3, colorSpaceID);
}
/** Converts a read-only external chunk into an internal one for easier use. */
createInternalChunk(data, timestamp, duration, type, additions = null) {
const internalChunk = {
data,
type,
timestamp,
duration,
additions,
};
return internalChunk;
}
/** Writes a block containing media data to the file. */
writeBlock(trackData, chunk) {
// Due to the interlacing algorithm, this code will be run once we've seen one chunk from every media track.
if (!this.segment) {
this.createTracks();
this.createSegment();
}
const msTimestamp = Math.round(1000 * chunk.timestamp);
// We wanna only finalize this cluster (and begin a new one) if we know that each track will be able to
// start the new one with a key frame.
const keyFrameQueuedEverywhere = this.trackDatas.every((otherTrackData) => {
if (trackData === otherTrackData) {
return chunk.type === 'key';
}
const firstQueuedSample = otherTrackData.chunkQueue[0];
if (firstQueuedSample) {
return firstQueuedSample.type === 'key';
}
return otherTrackData.track.source._closed;
});
let shouldCreateNewCluster = false;
if (!this.currentCluster) {
shouldCreateNewCluster = true;
}
else {
assert(this.currentClusterStartMsTimestamp !== null);
assert(this.currentClusterMaxMsTimestamp !== null);
const relativeTimestamp = msTimestamp - this.currentClusterStartMsTimestamp;
shouldCreateNewCluster = (keyFrameQueuedEverywhere
// This check is required because that means there is already a block with this timestamp in the
// CURRENT chunk, meaning that starting the next cluster at the same timestamp is forbidden (since
// the already-written block would belong into it instead).
&& msTimestamp > this.currentClusterMaxMsTimestamp
&& relativeTimestamp >= 1000 * (this.format._options.minimumClusterDuration ?? 1))
// The cluster would exceed its maximum allowed length. This puts us in an unfortunate position and forces
// us to begin the next cluster with a delta frame. Although this is undesirable, it is not forbidden by the
// spec and is supported by players.
|| relativeTimestamp > MAX_CLUSTER_TIMESTAMP_MS;
}
if (shouldCreateNewCluster) {
this.createNewCluster(msTimestamp);
}
const relativeTimestamp = msTimestamp - this.currentClusterStartMsTimestamp;
if (relativeTimestamp < MIN_CLUSTER_TIMESTAMP_MS) {
// The block lies too far in the past, it's not representable within this cluster
return;
}
const prelude = new Uint8Array(4);
const view = new DataView(prelude.buffer);
// 0x80 to indicate it's the last byte of a multi-byte number
view.setUint8(0, 0x80 | trackData.track.id);
view.setInt16(1, relativeTimestamp, false);
const msDuration = Math.round(1000 * chunk.duration);
if (msDuration === 0 && !chunk.additions) {
// No duration or additions, we can write out a SimpleBlock
view.setUint8(3, Number(chunk.type === 'key') << 7); // Flags (keyframe flag only present for SimpleBlock)
const simpleBlock = { id: EBMLId.SimpleBlock, data: [
prelude,
chunk.data,
] };
this.ebmlWriter.writeEBML(simpleBlock);
}
else {
const blockGroup = { id: EBMLId.BlockGroup, data: [
{ id: EBMLId.Block, data: [
prelude,
chunk.data,
] },
chunk.type === 'delta'
? {
id: EBMLId.ReferenceBlock,
data: new EBMLSignedInt(trackData.lastWrittenMsTimestamp - msTimestamp),
}
: null,
chunk.additions
? { id: EBMLId.BlockAdditions, data: [
{ id: EBMLId.BlockMore, data: [
{ id: EBMLId.BlockAdditional, data: chunk.additions },
{ id: EBMLId.BlockAddID, data: 1 },
] },
] }
: null,
msDuration > 0 ? { id: EBMLId.BlockDuration, data: msDuration } : null,
] };
this.ebmlWriter.writeEBML(blockGroup);
}
this.duration = Math.max(this.duration, msTimestamp + msDuration);
trackData.lastWrittenMsTimestamp = msTimestamp;
if (!this.trackDatasInCurrentCluster.has(trackData)) {
this.trackDatasInCurrentCluster.set(trackData, {
firstMsTimestamp: msTimestamp,
});
}
this.currentClusterMaxMsTimestamp = Math.max(this.currentClusterMaxMsTimestamp, msTimestamp);
}
/** Creates a new Cluster element to contain media chunks. */
createNewCluster(msTimestamp) {
if (this.currentCluster) {
this.finalizeCurrentCluster();
}
if (this.format._options.onCluster) {
this.writer.startTrackingWrites();
}
this.currentCluster = {
id: EBMLId.Cluster,
size: this.format._options.appendOnly ? -1 : CLUSTER_SIZE_BYTES,
data: [
{ id: EBMLId.Timestamp, data: msTimestamp },
],
};
this.ebmlWriter.writeEBML(this.currentCluster);
this.currentClusterStartMsTimestamp = msTimestamp;
this.currentClusterMaxMsTimestamp = msTimestamp;
this.trackDatasInCurrentCluster.clear();
}
finalizeCurrentCluster() {
assert(this.currentCluster);
if (!this.format._options.appendOnly) {
const clusterSize = this.writer.getPos() - this.ebmlWriter.dataOffsets.get(this.currentCluster);
const endPos = this.writer.getPos();
// Write the size now that we know it
this.writer.seek(this.ebmlWriter.offsets.get(this.currentCluster) + 4);
this.ebmlWriter.writeVarInt(clusterSize, CLUSTER_SIZE_BYTES);
this.writer.seek(endPos);
}
if (this.format._options.onCluster) {
assert(this.currentClusterStartMsTimestamp !== null);
const { data, start } = this.writer.stopTrackingWrites();
this.format._options.onCluster(data, start, this.currentClusterStartMsTimestamp / 1000);
}
const clusterOffsetFromSegment = this.ebmlWriter.offsets.get(this.currentCluster) - this.segmentDataOffset;
// Group tracks by their first timestamp and create a CuePoint for each unique timestamp
const groupedByTimestamp = new Map();
for (const [trackData, { firstMsTimestamp }] of this.trackDatasInCurrentCluster) {
if (!groupedByTimestamp.has(firstMsTimestamp)) {
groupedByTimestamp.set(firstMsTimestamp, []);
}
groupedByTimestamp.get(firstMsTimestamp).push(trackData);
}
const groupedAndSortedByTimestamp = [...groupedByTimestamp.entries()].sort((a, b) => a[0] - b[0]);
// Add CuePoints to the Cues element for better seeking
for (const [msTimestamp, trackDatas] of groupedAndSortedByTimestamp) {
assert(this.cues);
this.cues.data.push({ id: EBMLId.CuePoint, data: [
{ id: EBMLId.CueTime, data: msTimestamp },
// Create CueTrackPositions for each track that starts at this timestamp
...trackDatas.map((trackData) => {
return { id: EBMLId.CueTrackPositions, data: [
{ id: EBMLId.CueTrack, data: trackData.track.id },
{ id: EBMLId.CueClusterPosition, data: clusterOffsetFromSegment },
] };
}),
] });
}
}
// eslint-disable-next-line @typescript-eslint/no-misused-promises
async onTrackClose() {
const release = await this.mutex.acquire();
if (this.allTracksAreKnown()) {
this.allTracksKnown.resolve();
}
// Since a track is now closed, we may be able to write out chunks that were previously waiting
await this.interleaveChunks();
release();
}
/** Finalizes the file, making it ready for use. Must be called after all media chunks have been added. */
async finalize() {
const release = await this.mutex.acquire();
this.allTracksKnown.resolve();
if (!this.segment) {
this.createTracks();
this.createSegment();
}
// Flush any remaining queued chunks to the file
await this.interleaveChunks(true);
if (this.currentCluster) {
this.finalizeCurrentCluster();
}
assert(this.cues);
this.ebmlWriter.writeEBML(this.cues);
if (!this.format._options.appendOnly) {
const endPos = this.writer.getPos();
// Write the Segment size
const segmentSize = this.writer.getPos() - this.segmentDataOffset;
this.writer.seek(this.ebmlWriter.offsets.get(this.segment) + 4);
this.ebmlWriter.writeVarInt(segmentSize, SEGMENT_SIZE_BYTES);
// Write the duration of the media to the Segment
this.segmentDuration.data = new EBMLFloat64(this.duration);
this.writer.seek(this.ebmlWriter.offsets.get(this.segmentDuration));
this.ebmlWriter.writeEBML(this.segmentDuration);
// Fill in SeekHead position data and write it again
this.seekHead.data[0].data[1].data
= this.ebmlWriter.offsets.get(this.cues) - this.segmentDataOffset;
this.seekHead.data[1].data[1].data
= this.ebmlWriter.offsets.get(this.segmentInfo) - this.segmentDataOffset;
this.seekHead.data[2].data[1].data
= this.ebmlWriter.offsets.get(this.tracksElement) - this.segmentDataOffset;
this.writer.seek(this.ebmlWriter.offsets.get(this.seekHead));
this.ebmlWriter.writeEBML(this.seekHead);
this.writer.seek(endPos);
}
release();
}
}