feat: add support for multi-disc albums

app/api/spectrogram/route.ts

@@ -32,9 +32,14 @@ export async function POST(request: Request) {
             if ('error' in track) return;
 
             const trackNo = track.common?.track?.no;
+            const discNo = track.common?.disk?.no;
             if (trackNo === undefined || trackNo === null) return;
 
-            const outputFilename = `${trackNo}.png`;
+            const discPrefix = (discNo && discNo > 1) || tracks.some(t => !('error' in t) && (t.common?.disk?.no ?? 1) > 1)
+                ? `${discNo ?? 1}-`
+                : '';
+
+            const outputFilename = `${discPrefix}${trackNo}.png`;
             const outputPath = path.join(albumSpecDir, outputFilename);
             const relativePath = path.join(albumId, outputFilename);
             const publicUrl = `/api/spectrogram?path=${encodeURIComponent(relativePath)}`;
@@ -43,7 +48,7 @@ export async function POST(request: Request) {
 
             if (!exists) {
                 // Generate
-                const title = `${trackNo} - ${track.common?.title || track.filename}`;
+                const title = `${discPrefix}${trackNo} - ${track.common?.title || track.filename}`;
 
                 const args = [
                     track.path,