fix: use lamejs Mp3Encoder API for proper module initialization

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>

lib/audio/export.ts

@@ -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);

types/lamejs.d.ts

@@ -1,31 +1,15 @@
-declare module 'lamejs/src/js/MPEGMode' {
-  const MPEGMode: {
-    STEREO: number;
-    JOINT_STEREO: number;
-    DUAL_CHANNEL: number;
-    MONO: number;
-    NOT_SET: number;
-  };
-  export default MPEGMode;
-}
+declare module 'lamejs/src/js/index.js' {
+  export class Mp3Encoder {
+    constructor(channels: number, samplerate: number, kbps: number);
+    encodeBuffer(left: Int16Array, right: Int16Array): Int8Array;
+    flush(): Int8Array;
+  }
 
-declare module 'lamejs/src/js/Lame' {
-  export default class Lame {
-    lame_init(): any;
-    lame_init_params(gfp: any): number;
-    lame_encode_buffer(
-      gfp: any,
-      left: Int16Array,
-      right: Int16Array,
-      samples: number,
-      mp3buf: Int8Array,
-      mp3bufPos: number
-    ): number;
-    lame_encode_flush(gfp: any, mp3buf: Int8Array, mp3bufPos: number): number;
-    lame_close(gfp: any): number;
+  export class WavHeader {
+    dataOffset: number;
+    dataLen: number;
+    channels: number;
+    sampleRate: number;
+    static readHeader(dataView: DataView): WavHeader;
   }
 }
-
-declare module 'lamejs/src/js/BitStream' {
-  export default class BitStream {}
-}