Fix COVER mode MP3 failure: AUDIO_DIR path mismatch breaks file resolution for dit-vae

.env.example

@@ -39,7 +39,11 @@ MODELS_DIR=./models
 # ACESTEP_CPP_BRANCH=main
 
 # ── Storage ───────────────────────────────────────────────────────────────────
-AUDIO_DIR=./public/audio
+# Audio directory for generated songs and uploaded reference tracks.
+# Relative paths are resolved from the project root (APP_ROOT).
+# This is the single source of truth: LocalStorageProvider (writes),
+# Express /audio/ endpoint (serves), and the spawn service (reads) all use it.
+AUDIO_DIR=./server/public/audio
 
 # ── Auth ──────────────────────────────────────────────────────────────────────
 # Change this to a long random string in any multi-user or network-exposed setup.

server/src/config/index.ts

@@ -224,10 +224,11 @@ export const config = {
 
   storage: {
     provider: 'local' as const,
-    // Audio directory must match where LocalStorageProvider writes files and
-    // where Express serves /audio/ from (server/src/index.ts: '../public/audio').
-    // Both resolve to <server_root>/public/audio, so we use SERVER_ROOT here.
-    // AUDIO_DIR env override is still supported (resolved against APP_ROOT).
+    // Single source of truth for the audio directory.
+    // LocalStorageProvider, Express (/audio/), and the spawn service all read
+    // this value so they always point at the same filesystem location.
+    // Default: <server_root>/public/audio (SERVER_ROOT = server/).
+    // Override via AUDIO_DIR in .env (relative paths are resolved from APP_ROOT).
     audioDir: resolveFromRoot(process.env.AUDIO_DIR || path.join(SERVER_ROOT, 'public', 'audio')),
   },
 

server/src/index.ts

@@ -79,8 +79,9 @@ app.use(cors({
 
 app.use(express.json());
 
-// Serve static audio files
-app.use('/audio', express.static(path.join(__dirname, '../public/audio')));
+// Serve static audio files from the configured audio directory so that any
+// AUDIO_DIR env override is honoured consistently across upload, spawn, and serving.
+app.use('/audio', express.static(config.storage.audioDir));
 
 // Audio Editor (AudioMass) - needs relaxed CSP for inline scripts and external images
 app.use('/editor', (req, res, next) => {

server/src/services/acestep.ts

@@ -640,7 +640,8 @@ async function runViaSpawn(
     const batchSize = Math.min(Math.max(params.batchSize ?? 1, 1), 8);
     if (batchSize > 1) ditArgs.push('--batch', String(batchSize));
 
-    // Cover and repaint modes both require a source audio file
+    // Cover and repaint modes both require a source audio file.
+    // dit-vae reads WAV or MP3 natively (via dr_wav / dr_mp3 in audio.h).
     if (params.sourceAudioUrl) {
       const srcAudioPath = resolveAudioPath(params.sourceAudioUrl);
       ditArgs.push('--src-audio', srcAudioPath);

server/src/services/storage/local.ts

@@ -1,17 +1,16 @@
 import { writeFile, unlink, stat, mkdir, copyFile } from 'fs/promises';
 import path from 'path';
-import { fileURLToPath } from 'url';
 import type { StorageProvider } from './index.js';
-
-const __filename = fileURLToPath(import.meta.url);
-const __dirname = path.dirname(__filename);
-const AUDIO_DIR = path.join(__dirname, '../../../public/audio');
+import { config } from '../../config/index.js';
 
 export class LocalStorageProvider implements StorageProvider {
   private audioDir: string;
 
   constructor() {
-    this.audioDir = AUDIO_DIR;
+    // Derive the audio directory from the central config so that the storage
+    // provider always writes to the same location the spawn service resolves
+    // paths from (config.storage.audioDir, which honours the AUDIO_DIR env var).
+    this.audioDir = config.storage.audioDir;
   }
 
   async upload(key: string, data: Buffer, _contentType: string): Promise<string> {