Still lane: size the looped picture to the audio's real length

server/media-cache.js

@@ -523,11 +523,15 @@ export function createMediaCache({
     const niced = (args) => (nice ? run(nice, ['-n', '19', ffmpeg, ...args]) : run(ffmpeg, args));
     try {
       const at = String(Math.min(30, Math.floor(row.duration / 2)));
+      // The picture must last as long as the audio; -shortest cuts a 1 fps loop
+      // a few seconds early, so read the audio stream's own length.
+      const pa = await run(ffprobe, ['-v', 'error', '-select_streams', 'a:0', '-show_entries', 'stream=duration', '-of', 'csv=p=0', src]);
+      const seconds = Number(String(pa.stdout).trim()) > 0 ? Number(String(pa.stdout).trim()) : row.duration;
       const f = await niced(['-v', 'error', '-nostdin', '-y', '-ss', at, '-i', src, '-frames:v', '1',
         '-vf', 'scale=-2:min(720\\,ih)', frame]);
       if (f.code !== 0) throw new Error('still frame grab failed: ' + tail(f.stderr));
       const r = await niced(['-v', 'error', '-nostdin', '-y', '-loop', '1', '-framerate', '1', '-i', frame, '-i', src,
-        '-map', '0:v', '-map', '1:a:0', '-t', String(row.duration), '-shortest',
+        '-map', '0:v', '-map', '1:a:0', '-t', String(seconds),
         '-c:v', 'libx264', '-preset', 'medium', '-crf', String(transcode.crf), '-tune', 'stillimage',
         '-profile:v', 'high', '-level:v', '4.0', '-pix_fmt', 'yuv420p', '-g', '600', '-threads', threads,
         '-c:a', 'copy', '-movflags', '+faststart', '-f', 'mp4', out]);