feat(audio): add ffmpeg-backed audio converter for mp3/wav/ogg/flac/aac/m4a

src/converters/audio.js

@@ -0,0 +1,40 @@
+import { execFile } from 'node:child_process';
+import { promisify } from 'node:util';
+import { register } from './registry.js';
+
+const execFileAsync = promisify(execFile);
+
+export const AUDIO_FORMATS = ['mp3', 'wav', 'ogg', 'flac', 'aac', 'm4a'];
+
+const CODEC_ARGS = {
+  mp3: ['-c:a', 'libmp3lame'],
+  ogg: ['-c:a', 'libvorbis'],
+  aac: ['-c:a', 'aac'],
+  m4a: ['-c:a', 'aac'],
+  wav: ['-c:a', 'pcm_s16le'],
+  flac: ['-c:a', 'flac'],
+};
+
+const BITRATE_CAPABLE_FORMATS = ['mp3', 'ogg', 'aac', 'm4a'];
+
+export function registerAudioConverters() {
+  for (const sourceFormat of AUDIO_FORMATS) {
+    for (const targetFormat of AUDIO_FORMATS) {
+      if (sourceFormat === targetFormat) continue;
+      register({
+        family: 'audio',
+        sourceFormat,
+        targetFormat,
+        convert: async (inputPath, outputPath, { quality, timeoutMs } = {}) => {
+          const ffmpegPath = process.env.FFMPEG_PATH || 'ffmpeg';
+          const args = ['-y', '-i', inputPath, ...CODEC_ARGS[targetFormat]];
+          if (quality != null && BITRATE_CAPABLE_FORMATS.includes(targetFormat)) {
+            args.push('-b:a', `${quality}k`);
+          }
+          args.push(outputPath);
+          await execFileAsync(ffmpegPath, args, { timeout: timeoutMs });
+        },
+      });
+    }
+  }
+}