Add language getter to InputTrack

dev/demux.html

@@ -43,6 +43,8 @@
 		const videoTrack = await input.getPrimaryVideoTrack();
 		const sink = new Metamuxer.VideoFrameSink(videoTrack);
 
+		console.log(await videoTrack.getLanguageCode());
+
 		for await (const thing of sink.framesAtTimestamps([0.2, 1, 2, 423])) {
 			console.log(thing)
 		}

src/input-track.ts

@@ -7,6 +7,7 @@ export interface InputTrackBacking {
 	getCodec(): Promise<MediaCodec | null>;
 	getFirstTimestamp(): Promise<number>;
 	computeDuration(): Promise<number>;
+	getLanguageCode(): Promise<string>;
 }
 
 /** @public */
@@ -39,6 +40,10 @@ export abstract class InputTrack {
 	computeDuration() {
 		return this._backing.computeDuration();
 	}
+
+	getLanguageCode() {
+		return this._backing.getLanguageCode();
+	}
 }
 
 export interface InputVideoTrackBacking extends InputTrackBacking {

src/isobmff/isobmff-boxes.ts

@@ -11,6 +11,7 @@ import {
 	colorSpaceIsComplete,
 	IDENTITY_MATRIX,
 	rotationMatrix,
+	UNDETERMINED_LANGUAGE,
 } from '../misc';
 import {
 	AudioCodec,
@@ -429,7 +430,7 @@ export const mdhd = (
 	const u32OrU64 = needsU64 ? u64 : u32;
 
 	let language = 0;
-	for (const character of (trackData.track.metadata.languageCode ?? 'und')) {
+	for (const character of (trackData.track.metadata.languageCode ?? UNDETERMINED_LANGUAGE)) {
 		language <<= 5;
 		language += character.charCodeAt(0) - 0x60;
 	}

src/isobmff/isobmff-demuxer.ts

@@ -34,6 +34,7 @@ import {
 	last,
 	AsyncMutex,
 	findLastIndex,
+	UNDETERMINED_LANGUAGE,
 } from '../misc';
 import { Reader } from '../reader';
 import { EncodedAudioSample, EncodedVideoSample, PLACEHOLDER_DATA, SampleType } from '../sample';
@@ -47,6 +48,7 @@ type InternalTrack = {
 	durationInMovieTimescale: number;
 	durationInMediaTimescale: number;
 	rotation: Rotation;
+	languageCode: string;
 	sampleTableByteOffset: number;
 	sampleTable: SampleTable | null;
 	fragmentLookupTable: FragmentLookupTableEntry[] | null;
@@ -557,6 +559,7 @@ export class IsobmffDemuxer extends Demuxer {
 					durationInMovieTimescale: -1,
 					durationInMediaTimescale: -1,
 					rotation: 0,
+					languageCode: UNDETERMINED_LANGUAGE,
 					sampleTableByteOffset: -1,
 					sampleTable: null,
 					fragmentLookupTable: null,
@@ -642,6 +645,17 @@ export class IsobmffDemuxer extends Demuxer {
 					track.timescale = this.isobmffReader.readU32();
 					track.durationInMediaTimescale = this.isobmffReader.readU64();
 				}
+
+				let language = this.isobmffReader.readU16();
+
+				if (language > 0) {
+					track.languageCode = '';
+
+					for (let i = 0; i < 3; i++) {
+						track.languageCode = String.fromCharCode(0x60 + (language & 0b11111)) + track.languageCode;
+						language >>= 5;
+					}
+				}
 			}; break;
 
 			case 'hdlr': {
@@ -1689,6 +1703,10 @@ abstract class IsobmffTrackBacking<
 		return (lastSample?.timestamp ?? 0) + (lastSample?.duration ?? 0);
 	}
 
+	async getLanguageCode() {
+		return this.internalTrack.languageCode;
+	}
+
 	async getFirstTimestamp() {
 		const firstSample = await this.getFirstSample({ metadataOnly: true });
 		return firstSample?.timestamp ?? 0;

src/matroska/matroska-demuxer.ts

@@ -30,6 +30,7 @@ import {
 	MATRIX_COEFFICIENTS_MAP_INVERSE,
 	Rotation,
 	TRANSFER_CHARACTERISTICS_MAP_INVERSE,
+	UNDETERMINED_LANGUAGE,
 } from '../misc';
 import { Reader } from '../reader';
 import { EncodedAudioSample, EncodedVideoSample, PLACEHOLDER_DATA, SampleType } from '../sample';
@@ -107,6 +108,7 @@ type InternalTrack = {
 	inputTrack: InputTrack | null;
 	codecId: string | null;
 	codecPrivate: Uint8Array | null;
+	languageCode: string;
 	info:
 		| null
 		| {
@@ -583,6 +585,7 @@ export class MatroskaDemuxer extends Demuxer {
 					inputTrack: null,
 					codecId: null,
 					codecPrivate: null,
+					languageCode: UNDETERMINED_LANGUAGE,
 					info: null,
 				};
 
@@ -733,6 +736,12 @@ export class MatroskaDemuxer extends Demuxer {
 				this.currentTrack.codecPrivate = reader.readBytes(size);
 			}; break;
 
+			case EBMLId.Language: {
+				if (!this.currentTrack) break;
+
+				this.currentTrack.languageCode = reader.readString(size);
+			}; break;
+
 			case EBMLId.Video: {
 				if (this.currentTrack?.info?.type !== 'video') break;
 
@@ -967,6 +976,10 @@ abstract class MatroskaTrackBacking<
 		return (lastSample?.timestamp ?? 0) + (lastSample?.duration ?? 0);
 	}
 
+	async getLanguageCode() {
+		return this.internalTrack.languageCode;
+	}
+
 	async getFirstTimestamp() {
 		const firstSample = await this.getFirstSample({ metadataOnly: true });
 		return firstSample?.timestamp ?? 0;

src/matroska/matroska-muxer.ts

@@ -2,6 +2,7 @@ import {
 	COLOR_PRIMARIES_MAP,
 	MATRIX_COEFFICIENTS_MAP,
 	TRANSFER_CHARACTERISTICS_MAP,
+	UNDETERMINED_LANGUAGE,
 	assert,
 	colorSpaceIsComplete,
 	readBits,
@@ -241,7 +242,7 @@ export class MatroskaMuxer extends Muxer {
 				{ 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.Language, data: trackData.track.metadata.languageCode ?? UNDETERMINED_LANGUAGE },
 				{ id: EBMLId.CodecID, data: codecId },
 				{ id: EBMLId.CodecDelay, data: 0 },
 				{ id: EBMLId.SeekPreRoll, data: seekPreRollNs },

src/misc.ts

@@ -329,3 +329,5 @@ export const mapAsyncGenerator = <T, U>(
 export const clamp = (value: number, min: number, max: number) => {
 	return Math.max(min, Math.min(max, value));
 };
+
+export const UNDETERMINED_LANGUAGE = 'und';

src/wave/wave-demuxer.ts

@@ -3,7 +3,7 @@ import { Demuxer } from '../demuxer';
 import { Input } from '../input';
 import { InputAudioTrack, InputAudioTrackBacking } from '../input-track';
 import { SampleRetrievalOptions } from '../media-sink';
-import { assert } from '../misc';
+import { assert, UNDETERMINED_LANGUAGE } from '../misc';
 import { Reader } from '../reader';
 import { EncodedAudioSample, PLACEHOLDER_DATA } from '../sample';
 import { RiffReader } from './riff-reader';
@@ -215,6 +215,10 @@ class WaveAudioTrackBacking implements InputAudioTrackBacking {
 		return this.demuxer.audioInfo.sampleRate;
 	}
 
+	async getLanguageCode() {
+		return UNDETERMINED_LANGUAGE;
+	}
+
 	async getFirstTimestamp() {
 		return 0;
 	}