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Make MP3 next frame location more strict for better recovery (fixes #382), fix Date timezone for ID3 tags

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This commit is contained in:
Vanilagy
2026-05-22 11:31:26 +02:00
parent 149a2b4571
commit 85a80972a0
9 changed files with 70 additions and 26 deletions
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packages/mp3-encoder/src/index.ts
+2 -2
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@@ -7,7 +7,7 @@
*/
import { CustomAudioEncoder, AudioCodec, AudioSample, EncodedPacket, registerEncoder } from 'mediabunny';
import { FRAME_HEADER_SIZE, readMp3FrameHeader, SAMPLING_RATES } from '../../../shared/mp3-misc';
import { MP3_FRAME_HEADER_SIZE, readMp3FrameHeader, SAMPLING_RATES } from '../../../shared/mp3-misc';
import type { WorkerCommand, WorkerResponse, WorkerResponseData } from './shared';
// @ts-expect-error An esbuild plugin handles this, TypeScript doesn't need to understand
import createWorker from './encode.worker';
@@ -160,7 +160,7 @@ class Mp3Encoder extends CustomAudioEncoder {
this.currentBufferOffset = requiredBufferSize;
let pos = 0;
while (pos <= this.currentBufferOffset - FRAME_HEADER_SIZE) {
while (pos <= this.currentBufferOffset - MP3_FRAME_HEADER_SIZE) {
const word = new DataView(this.buffer.buffer).getUint32(pos, false);
const header = readMp3FrameHeader(word, null).header;
if (!header) {
shared/mp3-misc.ts
+7 -2
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@@ -6,7 +6,7 @@
* file, You can obtain one at https://mozilla.org/MPL/2.0/.
*/
export const FRAME_HEADER_SIZE = 4;
export const MP3_FRAME_HEADER_SIZE = 4;
export const SAMPLING_RATES = [44100, 48000, 32000];
export const KILOBIT_RATES = [
// lowSamplingFrequency === 0
@@ -122,7 +122,8 @@ export const readMp3FrameHeader = (word: number, remainingBytes: number | null):
const layer = (secondByte >> 1) & 0x3;
const bitrateIndex = (thirdByte >> 4) & 0xf;
const frequencyIndex = ((thirdByte >> 2) & 0x3) % 3;
const frequencyIndex = ((thirdByte >> 2) & 0x3) % 3; // FFmpeg effectively does % 3 (but in a roundabout way)
const padding = (thirdByte >> 1) & 0x1;
const channel = (fourthByte >> 6) & 0x3;
@@ -212,3 +213,7 @@ export enum XingFlags {
FileSize = 1 << 1,
Toc = 1 << 2,
}
export const getMp3ChannelCount = (channel: number) => {
return channel === 3 ? 1 : 2;
};
src/id3.ts
+2 -2
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@@ -93,7 +93,7 @@ export const parseId3V1Tag = (slice: FileSlice, tags: MetadataTags) => {
const yearText = readId3V1String(slice, 4);
const year = Number.parseInt(yearText, 10);
if (Number.isInteger(year) && year > 0) {
tags.date ??= new Date(year, 0, 1);
tags.date ??= new Date(String(year)); // String so that it parses as UTC
}
const commentBytes = readBytes(slice, 30);
@@ -339,7 +339,7 @@ export const parseId3V2Tag = (slice: FileSlice, header: Id3V2Header, tags: Metad
const year = Number.parseInt(yearText, 10);
if (Number.isInteger(year)) {
tags.date ??= new Date(year, 0, 1);
tags.date ??= new Date(String(year)); // String so that it parses as UTC
}
}; break;
src/input-format.ts
+2 -2
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@@ -22,7 +22,7 @@ import {
} from './matroska/ebml';
import { MatroskaDemuxer } from './matroska/matroska-demuxer';
import { Mp3Demuxer } from './mp3/mp3-demuxer';
import { FRAME_HEADER_SIZE, getXingOffset, INFO, XING } from '../shared/mp3-misc';
import { MP3_FRAME_HEADER_SIZE, getXingOffset, INFO, XING } from '../shared/mp3-misc';
import { ID3_V2_HEADER_SIZE, readId3V2Header } from './id3';
import { readNextMp3FrameHeader } from './mp3/mp3-reader';
import { OggDemuxer } from './ogg/ogg-demuxer';
@@ -330,7 +330,7 @@ export class Mp3InputFormat extends InputFormat {
// Fine, we found one frame header, but we're still not entirely sure this is MP3. Let's check if we can find
// another header right after it:
const secondResult = await readNextMp3FrameHeader(input._reader, currentPos, currentPos + FRAME_HEADER_SIZE);
const secondResult = await readNextMp3FrameHeader(input._reader, currentPos, currentPos + MP3_FRAME_HEADER_SIZE);
if (!secondResult) {
return false;
}
src/mp3/mp3-demuxer.ts
+9 -10
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@@ -28,6 +28,7 @@ import {
XING,
XingFlags,
computeAverageMp3FrameSize,
getMp3ChannelCount,
} from '../../shared/mp3-misc';
import {
ID3_V1_TAG_SIZE,
@@ -108,7 +109,12 @@ export class Mp3Demuxer extends Demuxer {
}
}
const result = await readNextMp3FrameHeader(this.reader, this.lastLoadedPos, this.reader.fileSize);
const result = await readNextMp3FrameHeader(
this.reader,
this.lastLoadedPos,
this.reader.fileSize,
this.firstFrameHeader,
);
if (!result) {
this.lastSampleLoaded = true;
return;
@@ -157,13 +163,6 @@ export class Mp3Demuxer extends Demuxer {
this.firstFrameHeaderPos = result.startPos;
}
if (header.sampleRate !== this.firstFrameHeader.sampleRate) {
console.warn(
`MP3 changed sample rate mid-file: ${this.firstFrameHeader.sampleRate} Hz to ${header.sampleRate} Hz.`
+ ` Might be a bug, so please report this file.`,
);
}
const sampleDuration = header.audioSamplesInFrame / this.firstFrameHeader.sampleRate;
const sample: Sample = {
timestamp: this.nextTimestampInSamples / this.firstFrameHeader.sampleRate,
@@ -332,7 +331,7 @@ class Mp3AudioTrackBacking implements InputAudioTrackBacking {
getNumberOfChannels() {
assert(this.demuxer.firstFrameHeader);
return this.demuxer.firstFrameHeader.channel === 3 ? 1 : 2;
return getMp3ChannelCount(this.demuxer.firstFrameHeader.channel);
}
getSampleRate() {
@@ -351,7 +350,7 @@ class Mp3AudioTrackBacking implements InputAudioTrackBacking {
return {
codec: 'mp3',
numberOfChannels: this.demuxer.firstFrameHeader.channel === 3 ? 1 : 2,
numberOfChannels: getMp3ChannelCount(this.demuxer.firstFrameHeader.channel),
sampleRate: this.demuxer.firstFrameHeader.sampleRate,
};
}
src/mp3/mp3-reader.ts
+21 -6
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@@ -6,10 +6,15 @@
* file, You can obtain one at https://mozilla.org/MPL/2.0/.
*/
import { FRAME_HEADER_SIZE, Mp3FrameHeader, readMp3FrameHeader } from '../../shared/mp3-misc';
import { MP3_FRAME_HEADER_SIZE, getMp3ChannelCount, Mp3FrameHeader, readMp3FrameHeader } from '../../shared/mp3-misc';
import { Reader, readU32Be } from '../reader';
export const readNextMp3FrameHeader = async (reader: Reader, startPos: number, until: number | null): Promise<{
export const readNextMp3FrameHeader = async (
reader: Reader,
startPos: number,
until: number | null,
ref: Mp3FrameHeader | null = null,
): Promise<{
header: Mp3FrameHeader;
startPos: number;
} | null> => {
@@ -21,11 +26,11 @@ export const readNextMp3FrameHeader = async (reader: Reader, startPos: number, u
? Math.min(CHUNK_SIZE, until - currentPos)
: CHUNK_SIZE;
let slice = reader.requestSliceRange(currentPos, FRAME_HEADER_SIZE, maxLength);
let slice = reader.requestSliceRange(currentPos, MP3_FRAME_HEADER_SIZE, maxLength);
if (slice instanceof Promise) slice = await slice;
if (!slice || slice.length < FRAME_HEADER_SIZE) break;
if (!slice || slice.length < MP3_FRAME_HEADER_SIZE) break;
while (slice.remainingLength >= FRAME_HEADER_SIZE) {
while (slice.remainingLength >= MP3_FRAME_HEADER_SIZE) {
const posBeforeRead = slice.filePos;
const word = readU32Be(slice);
const remainingBytes = reader.fileSize !== null
@@ -33,7 +38,17 @@ export const readNextMp3FrameHeader = async (reader: Reader, startPos: number, u
: null;
const result = readMp3FrameHeader(word, remainingBytes);
if (result.header) {
if (
result.header
&& (!ref || (
// This condition helps us recover malformed streams
// https://stackoverflow.com/a/20884944
result.header.sampleRate === ref.sampleRate
&& result.header.mpegVersionId === ref.mpegVersionId
&& result.header.layer === ref.layer
&& getMp3ChannelCount(result.header.channel) === getMp3ChannelCount(ref.channel)
))
) {
return { header: result.header, startPos: currentPos };
}
src/mpeg-ts/mpeg-ts-demuxer.ts
+6 -2
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@@ -63,7 +63,11 @@ import {
TRANSFER_CHARACTERISTICS_MAP_INVERSE,
UNDETERMINED_LANGUAGE,
} from '../misc';
import { FRAME_HEADER_SIZE as MP3_FRAME_HEADER_SIZE, readMp3FrameHeader } from '../../shared/mp3-misc';
import {
MP3_FRAME_HEADER_SIZE,
getMp3ChannelCount,
readMp3FrameHeader,
} from '../../shared/mp3-misc';
import { EncodedPacket, PacketType, PLACEHOLDER_DATA } from '../packet';
import { FileSlice, readBytes, Reader, readU16Be, readU32Be, readU8 } from '../reader';
import { buildMpegTsMimeType, MpegTsStreamType, TIMESCALE, TS_PACKET_SIZE } from './mpeg-ts-misc';
@@ -629,7 +633,7 @@ export class MpegTsDemuxer extends Demuxer {
);
}
elementaryStream.info.numberOfChannels = result.header.channel === 3 ? 1 : 2;
elementaryStream.info.numberOfChannels = getMp3ChannelCount(result.header.channel);
elementaryStream.info.sampleRate = result.header.sampleRate;
} else if (elementaryStream.info.codec === 'ac3') {
const frameInfo = parseAc3SyncFrame(context.suppliedPacket.data);
test/browser/mp3.test.ts
+21
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@@ -0,0 +1,21 @@
import { test } from 'vitest';
import { Input } from '../../src/input.js';
import { UrlSource } from '../../src/source.js';
import { ALL_FORMATS } from '../../src/input-format.js';
import { assert } from '../../src/misc.js';
import { AudioSampleSink } from '../../src/media-sink.js';
// "joined" in the sense that it was two separate MP3s that were spliced together (I think)
test('Can decode malformed joined MP3', async () => {
using input = new Input({
source: new UrlSource('/malformed-join.mp3'),
formats: ALL_FORMATS,
});
const audioTrack = await input.getPrimaryAudioTrack();
assert(audioTrack);
const sink = new AudioSampleSink(audioTrack);
// eslint-disable-next-line @typescript-eslint/no-unused-vars
for await (using sample of sink.samples());
});
test/public/malformed-join.mp3
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