Ship extension queues, library extend, and smoother seam stitching.

Users can pre-queue extensions, extend from the library with p2 titles, blend seams with xfade, and a unreadable catalog is no longer replaced with an empty one.

Co-authored-by: Cursor <cursoragent@cursor.com>

server/utils/ffmpeg.ts

@@ -92,6 +92,132 @@ export async function probeHasAudio(filePath: string) {
   }
 }
 
+const XFADE_DURATION = 0.12
+
+async function probeDuration(filePath: string) {
+  const out = await runFfprobe([
+    '-v', 'error',
+    '-show_entries', 'format=duration',
+    '-of', 'default=nokey=1:noprint_wrappers=1',
+    filePath
+  ])
+  const duration = Number(out)
+  if (!Number.isFinite(duration) || duration <= 0) {
+    throw new Error('Could not read video duration')
+  }
+  return duration
+}
+
+async function probeFps(filePath: string) {
+  const out = await runFfprobe([
+    '-v', 'error',
+    '-select_streams', 'v:0',
+    '-show_entries', 'stream=avg_frame_rate,r_frame_rate',
+    '-of', 'default=nokey=1:noprint_wrappers=1',
+    filePath
+  ])
+  const line = out.split(/\r?\n/).map(item => item.trim()).find(Boolean) || ''
+  const [num, den] = line.split('/').map(Number)
+  if (Number.isFinite(num) && Number.isFinite(den) && den > 0) return num / den
+  const fps = Number(line)
+  return Number.isFinite(fps) && fps > 0 ? fps : 24
+}
+
+async function probeSize(filePath: string) {
+  const out = await runFfprobe([
+    '-v', 'error',
+    '-select_streams', 'v:0',
+    '-show_entries', 'stream=width,height',
+    '-of', 'csv=p=0',
+    filePath
+  ])
+  const [width, height] = out.split(',').map(Number)
+  return {
+    width: Number.isFinite(width) && width > 0 ? width : 1344,
+    height: Number.isFinite(height) && height > 0 ? height : 768
+  }
+}
+
+async function trimLeadingFrame(inputPath: string, outputPath: string) {
+  const fps = await probeFps(inputPath)
+  const hasAudio = await probeHasAudio(inputPath)
+  const args = [
+    '-y',
+    '-i', inputPath,
+    '-vf', 'trim=start_frame=1,setpts=PTS-STARTPTS'
+  ]
+  if (hasAudio) {
+    args.push('-af', `atrim=start=${(1 / fps).toFixed(6)},asetpts=PTS-STARTPTS`, '-c:a', 'aac')
+  } else {
+    args.push('-an')
+  }
+  args.push(
+    '-c:v', 'libx264',
+    '-preset', 'fast',
+    '-crf', '17',
+    '-pix_fmt', 'yuv420p',
+    '-movflags', '+faststart',
+    outputPath
+  )
+  await runFfmpeg(args, 180000)
+  if (!existsSync(outputPath)) {
+    throw new Error('FFmpeg did not write the trimmed extension segment')
+  }
+}
+
+async function xfadeStitch(part1Path: string, part2Path: string, outputPath: string) {
+  const [duration1, duration2, fps, size, audio1, audio2] = await Promise.all([
+    probeDuration(part1Path),
+    probeDuration(part2Path),
+    probeFps(part1Path),
+    probeSize(part1Path),
+    probeHasAudio(part1Path),
+    probeHasAudio(part2Path)
+  ])
+  const fade = Math.min(
+    XFADE_DURATION,
+    Math.max(0.04, duration1 - 0.05),
+    Math.max(0.04, duration2 - 0.05)
+  )
+  const offset = Math.max(0, Number((duration1 - fade).toFixed(3)))
+  const fpsLabel = Number.isInteger(fps) ? String(fps) : fps.toFixed(3)
+  const prepare = `fps=${fpsLabel},scale=${size.width}:${size.height}:flags=bicubic,format=yuv420p,setpts=PTS-STARTPTS`
+  const videoFilter = `[0:v]${prepare}[v0];[1:v]${prepare}[v1];[v0][v1]xfade=transition=fade:duration=${fade.toFixed(3)}:offset=${offset},setpts=PTS-STARTPTS[v]`
+  const encode = [
+    '-c:v', 'libx264',
+    '-preset', 'fast',
+    '-crf', '17',
+    '-pix_fmt', 'yuv420p',
+    '-movflags', '+faststart'
+  ]
+  if (audio1 && audio2) {
+    await runFfmpeg([
+      '-y',
+      '-i', part1Path,
+      '-i', part2Path,
+      '-filter_complex', `${videoFilter};[0:a]asetpts=PTS-STARTPTS[a0];[1:a]asetpts=PTS-STARTPTS[a1];[a0][a1]acrossfade=d=${fade.toFixed(3)}:c1=tri:c2=tri[a]`,
+      '-map', '[v]',
+      '-map', '[a]',
+      ...encode,
+      '-c:a', 'aac',
+      outputPath
+    ], 300000)
+  } else {
+    await runFfmpeg([
+      '-y',
+      '-i', part1Path,
+      '-i', part2Path,
+      '-filter_complex', videoFilter,
+      '-map', '[v]',
+      ...encode,
+      outputPath
+    ], 300000)
+  }
+  if (!existsSync(outputPath)) {
+    throw new Error('FFmpeg did not write the blended video')
+  }
+}
+
 export async function concatMp4(part1Path: string, part2Path: string, outputPath: string) {
   const listPath = join(dirname(outputPath), 'concat_list.txt')
   writeFileSync(listPath, `file '${concatPath(part1Path)}'\nfile '${concatPath(part2Path)}'\n`)
@@ -111,7 +237,7 @@ export async function concatMp4(part1Path: string, part2Path: string, outputPath
           '-map', '[a]',
           '-c:v', 'libx264',
           '-preset', 'fast',
-          '-crf', '18',
+          '-crf', '17',
           '-pix_fmt', 'yuv420p',
           '-c:a', 'aac',
           '-movflags', '+faststart',
@@ -126,7 +252,7 @@ export async function concatMp4(part1Path: string, part2Path: string, outputPath
           '-map', '[v]',
           '-c:v', 'libx264',
           '-preset', 'fast',
-          '-crf', '18',
+          '-crf', '17',
           '-pix_fmt', 'yuv420p',
           '-movflags', '+faststart',
           outputPath
@@ -145,11 +271,24 @@ export async function concatMp4(part1Path: string, part2Path: string, outputPath
 
 export async function stitchExtension(params: { part1Path: string; part2: Buffer; tmpDir: string }) {
   const part2Path = join(params.tmpDir, 'part2.mp4')
+  const trimmedPath = join(params.tmpDir, 'part2_trim.mp4')
   const finalPath = join(params.tmpDir, 'final_stitched_video.mp4')
   writeFileSync(part2Path, params.part2)
-  await concatMp4(params.part1Path, part2Path, finalPath)
+  try {
+    await trimLeadingFrame(part2Path, trimmedPath)
+    await xfadeStitch(params.part1Path, trimmedPath, finalPath)
+  } catch (blendError) {
+    try {
+      const trimmedReady = existsSync(trimmedPath)
+      await concatMp4(params.part1Path, trimmedReady ? trimmedPath : part2Path, finalPath)
+    } catch (concatError) {
+      const blendMessage = blendError instanceof Error ? blendError.message : String(blendError)
+      const concatMessage = concatError instanceof Error ? concatError.message : String(concatError)
+      throw new Error(`Seam blend failed (${blendMessage}). Concat fallback also failed (${concatMessage}).`)
+    }
+  }
   const stitched = readFileSync(finalPath)
-  for (const extra of [part2Path, join(params.tmpDir, 'concat_list.txt'), join(params.tmpDir, 'last_frame.png')]) {
+  for (const extra of [part2Path, trimmedPath, join(params.tmpDir, 'concat_list.txt'), join(params.tmpDir, 'last_frame.png')]) {
     try { unlinkSync(extra) } catch { /* ignore */ }
   }
   return stitched