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Implement MP3 muxer

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Vanilagy
2025-01-26 11:45:56 +01:00
parent 7205d9445b
commit d3566305df
11 changed files with 482 additions and 148 deletions
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src/mp3/mp3-demuxer.ts
+6 -8
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@@ -5,7 +5,8 @@ import { InputAudioTrack, InputAudioTrackBacking } from '../input-track';
import { SampleRetrievalOptions } from '../media-sink';
import { assert, binarySearchExact, binarySearchLessOrEqual, last, UNDETERMINED_LANGUAGE } from '../misc';
import { EncodedAudioSample, PLACEHOLDER_DATA } from '../sample';
import { FrameHeader, Mp3Reader } from './mp3-reader';
import { FrameHeader, getXingOffset, INFO, XING } from './mp3-misc';
import { Mp3Reader } from './mp3-reader';
const AUDIO_SAMPLES_PER_FRAME = 1152;
@@ -54,13 +55,10 @@ export class Mp3Demuxer extends Demuxer {
break;
}
const xingOffset = header.mpegVersionId === 3
? (header.channelCount === 1 ? 21 : 36)
: (header.channelCount === 1 ? 13 : 21);
const xingOffset = getXingOffset(header.mpegVersionId, header.channel);
this.reader.pos = header.startPos + xingOffset;
const word = this.reader.readU32();
const isXing = word === 0x58696e67 // 'Xing'
|| word === 0x496e666f; // 'Info'
const isXing = word === XING || word === INFO;
this.reader.pos = header.startPos + header.totalSize - 1; // -1 in case the frame is 1 byte too short
@@ -137,7 +135,7 @@ class Mp3AudioTrackBacking implements InputAudioTrackBacking {
async getNumberOfChannels() {
assert(this.demuxer.firstFrameHeader);
return this.demuxer.firstFrameHeader.channelCount;
return this.demuxer.firstFrameHeader.channel === 3 ? 1 : 2;
}
async getSampleRate() {
@@ -150,7 +148,7 @@ class Mp3AudioTrackBacking implements InputAudioTrackBacking {
return {
codec: 'mp3',
numberOfChannels: this.demuxer.firstFrameHeader.channelCount,
numberOfChannels: this.demuxer.firstFrameHeader.channel === 3 ? 1 : 2,
sampleRate: this.demuxer.firstFrameHeader.sampleRate,
};
}