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FLAC: Add appendOnly option for FlaxMuxer, fix FlacDemuxer reading it (#325)

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* implement in FlacOutputFormatOptions

* implement in flac-muxer.ts

* Fix demuxer: Handle minimumFrameSize = 0, maxiumFrameSize = 0

* add a test

* Update flac-demuxer.ts

* Update flac.test.ts

* clean up comments for minima and maxima

* Add FlacOutputFormatOptions.appendOnly to docs

---------

Co-authored-by: Vanilagy <[email protected]>
This commit is contained in:
Jonny Burger
2026-03-19 13:43:28 +00:00
committed by GitHub
co-authored by Vanilagy
parent 0d50526ff6
commit 31d86331ec
5 changed files with 146 additions and 40 deletions
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src/flac/flac-muxer.ts
+70 -36
View File
@@ -50,6 +50,10 @@ export class FlacMuxer extends Muxer {
this.writer = output._writer;
this.format = format;
if (this.format._options.appendOnly) {
this.writer.ensureMonotonicity = true;
}
}
async start() {
@@ -165,7 +169,9 @@ export class FlacMuxer extends Muxer {
}
writeVorbisCommentAndPictureBlock() {
this.writer.seek(STREAMINFO_SIZE + FLAC_HEADER.byteLength);
if (!this.format._options.appendOnly) {
this.writer.seek(STREAMINFO_SIZE + FLAC_HEADER.byteLength);
}
if (metadataTagsAreEmpty(this.output._metadataTags)) {
this.metadataWritten = true;
return;
@@ -233,6 +239,30 @@ export class FlacMuxer extends Muxer {
descriptionBitstream.skipBits(103 + 64);
const bitsPerSample = descriptionBitstream.readBits(5) + 1;
this.bitsPerSample = bitsPerSample;
if (this.format._options.appendOnly) {
// Write STREAMINFO immediately since we can't seek back later.
this.writeHeader({
// https://www.rfc-editor.org/rfc/rfc9639.html#name-streaminfo
// Per RFC 9639, min/max block sizes can be looser than
// actual values, so we use the full valid range (16–65535).
// "The actual max block size MAY be smaller than what's
// listed, and the actual min (excluding last block) MAY be
// larger. This is because the encoder has to write these
// fields before receiving any input audio data and cannot
// know beforehand what block sizes it will use."
minimumBlockSize: 16,
maximumBlockSize: 65535,
// https://www.rfc-editor.org/rfc/rfc9639.html#name-streaminfo
// "A value of 0 signifies that the value is not known."
minimumFrameSize: 0,
maximumFrameSize: 0,
sampleRate: this.sampleRate,
channels: this.channels,
bitsPerSample: this.bitsPerSample,
totalSamples: 0,
});
}
}
if (!this.metadataWritten) {
@@ -251,8 +281,10 @@ export class FlacMuxer extends Muxer {
readCodedNumber(slice); // num
const blockSize = readBlockSize(slice, blockSizeOrUncommon);
this.blockSizes.push(blockSize);
this.frameSizes.push(packet.data.length);
if (!this.format._options.appendOnly) {
this.blockSizes.push(blockSize);
this.frameSizes.push(packet.data.length);
}
const startPos = this.writer.getPos();
this.writer.write(packet.data);
@@ -274,43 +306,45 @@ export class FlacMuxer extends Muxer {
async finalize(): Promise<void> {
const release = await this.mutex.acquire();
let minimumBlockSize = Infinity;
let maximumBlockSize = 0;
let minimumFrameSize = Infinity;
let maximumFrameSize = 0;
let totalSamples = 0;
for (let i = 0; i < this.blockSizes.length; i++) {
minimumFrameSize = Math.min(minimumFrameSize, this.frameSizes[i]!);
maximumFrameSize = Math.max(maximumFrameSize, this.frameSizes[i]!);
maximumBlockSize = Math.max(maximumBlockSize, this.blockSizes[i]!);
totalSamples += this.blockSizes[i]!;
if (!this.format._options.appendOnly) {
let minimumBlockSize = Infinity;
let maximumBlockSize = 0;
let minimumFrameSize = Infinity;
let maximumFrameSize = 0;
let totalSamples = 0;
for (let i = 0; i < this.blockSizes.length; i++) {
minimumFrameSize = Math.min(minimumFrameSize, this.frameSizes[i]!);
maximumFrameSize = Math.max(maximumFrameSize, this.frameSizes[i]!);
maximumBlockSize = Math.max(maximumBlockSize, this.blockSizes[i]!);
totalSamples += this.blockSizes[i]!;
// Excluding the last frame from block size calculation
// https://www.rfc-editor.org/rfc/rfc9639.html#name-streaminfo
// "The minimum block size (in samples) used in the stream, excluding the last block."
const isLastFrame = i === this.blockSizes.length - 1;
if (isLastFrame) {
continue;
// Excluding the last frame from block size calculation
// https://www.rfc-editor.org/rfc/rfc9639.html#name-streaminfo
// "The minimum block size (in samples) used in the stream, excluding the last block."
const isLastFrame = i === this.blockSizes.length - 1;
if (isLastFrame) {
continue;
}
minimumBlockSize = Math.min(minimumBlockSize, this.blockSizes[i]!);
}
minimumBlockSize = Math.min(minimumBlockSize, this.blockSizes[i]!);
assert(this.sampleRate !== null);
assert(this.channels !== null);
assert(this.bitsPerSample !== null);
this.writer.seek(4);
this.writeHeader({
minimumBlockSize,
maximumBlockSize,
minimumFrameSize,
maximumFrameSize,
sampleRate: this.sampleRate,
channels: this.channels,
bitsPerSample: this.bitsPerSample,
totalSamples,
});
}
assert(this.sampleRate !== null);
assert(this.channels !== null);
assert(this.bitsPerSample !== null);
this.writer.seek(4);
this.writeHeader({
minimumBlockSize,
maximumBlockSize,
minimumFrameSize,
maximumFrameSize,
sampleRate: this.sampleRate,
channels: this.channels,
bitsPerSample: this.bitsPerSample,
totalSamples,
});
release();
}
}