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Add setting track language code, add proper AV1 CodecPrivate for Matroska muxer

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Vanilagy
2025-01-15 20:00:29 +01:00
parent 9af3e6eb66
commit 2bec661985
7 changed files with 120 additions and 59 deletions
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src/matroska/matroska-muxer.ts
+32
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@@ -32,6 +32,7 @@ import {
import {
PCM_CODECS,
PcmAudioCodec,
generateAv1CodecConfigurationFromCodecString,
parsePcmCodec,
validateAudioChunkMetadata,
validateSubtitleMetadata,
@@ -220,11 +221,30 @@ export class MatroskaMuxer extends Muxer {
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 view = ArrayBuffer.isView(description)
? new DataView(description.buffer, description.byteOffset, description.byteLength)
: new DataView(description);
// Read the value from the Opus Identification Header
seekPreRollNs = Math.round(1e9 * (view.getUint16(10, true) / 48000));
}
}
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 ?? 'und' },
{ 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),
@@ -381,6 +401,18 @@ export class MatroskaMuxer extends Muxer {
lastWrittenMsTimestamp: null,
};
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);