Add language getter to InputTrack

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;