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fix: use lamejs Mp3Encoder API for proper module initialization

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Switched from low-level Lame API to Mp3Encoder class which:
- Properly initializes all required modules (Lame, BitStream, etc.)
- Handles module dependencies via setModules() calls
- Provides a simpler encodeBuffer/flush API
- Resolves "init_bit_stream_w is not defined" error

Updated TypeScript declarations to export Mp3Encoder and WavHeader
from lamejs/src/js/index.js

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>
This commit is contained in:
Sebastian Krüger
2025-11-19 08:19:48 +01:00
parent 51114330ea
commit c3e295f695
2 changed files with 23 additions and 63 deletions
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46
lib/audio/export.ts
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@@ -136,12 +136,8 @@ export async function audioBufferToMp3(
audioBuffer: AudioBuffer,
options: ExportOptions = { format: 'mp3', bitrate: 192 }
): Promise<ArrayBuffer> {
// Import lamejs modules directly
const [{ default: MPEGMode }, { default: Lame }, { default: BitStream }] = await Promise.all([
import('lamejs/src/js/MPEGMode'),
import('lamejs/src/js/Lame'),
import('lamejs/src/js/BitStream'),
]);
// Import Mp3Encoder from lamejs
const { Mp3Encoder } = await import('lamejs/src/js/index.js');
const { bitrate = 192, normalize } = options;
const numberOfChannels = Math.min(audioBuffer.numberOfChannels, 2); // MP3 supports max 2 channels
@@ -171,51 +167,31 @@ export async function audioBufferToMp3(
rightPcm[i] = Math.max(-32768, Math.min(32767, (right[i] / peak) * 32767));
}
// Create encoder using lamejs modules
const lame = new Lame();
const gfp = lame.lame_init();
gfp.num_channels = numberOfChannels;
gfp.in_samplerate = sampleRate;
gfp.brate = bitrate;
gfp.mode = numberOfChannels === 1 ? MPEGMode.MONO : MPEGMode.STEREO;
gfp.quality = 3; // 0=best (very slow), 9=worst (fast)
gfp.write_id3tag_automatic = 0;
lame.lame_init_params(gfp);
// Create MP3 encoder
const mp3encoder = new Mp3Encoder(numberOfChannels, sampleRate, bitrate);
const mp3Data: Int8Array[] = [];
const mp3buf = new Int8Array(samples * 1.25 + 7200); // Estimate output size
const sampleBlockSize = 1152; // Standard MP3 frame size
// Encode in blocks
for (let i = 0; i < samples; i += sampleBlockSize) {
const leftChunk = leftPcm.subarray(i, Math.min(i + sampleBlockSize, samples));
const rightChunk = numberOfChannels > 1
? rightPcm.subarray(i, Math.min(i + sampleBlockSize, samples))
: leftChunk;
const bytesEncoded = lame.lame_encode_buffer(
gfp,
leftChunk,
rightChunk,
leftChunk.length,
mp3buf,
0
);
if (bytesEncoded > 0) {
mp3Data.push(new Int8Array(mp3buf.subarray(0, bytesEncoded)));
const mp3buf = mp3encoder.encodeBuffer(leftChunk, rightChunk);
if (mp3buf.length > 0) {
mp3Data.push(mp3buf);
}
}
// Flush remaining data
const flushBytes = lame.lame_encode_flush(gfp, mp3buf, 0);
if (flushBytes > 0) {
mp3Data.push(new Int8Array(mp3buf.subarray(0, flushBytes)));
const mp3buf = mp3encoder.flush();
if (mp3buf.length > 0) {
mp3Data.push(mp3buf);
}
lame.lame_close(gfp);
// Combine all chunks
const totalLength = mp3Data.reduce((acc, arr) => acc + arr.length, 0);
const result = new Uint8Array(totalLength);