diff --git a/main.js b/main.js
index 4c0bcbe..362240c 100644
--- a/main.js
+++ b/main.js
@@ -309,13 +309,22 @@ function transcodeToMp4(input, output, opts) {
   const h = (opts && opts.h) || 1080;
   // Cover the target frame then centre-crop, so the chosen aspect is filled
   // without distortion.
-  const vf = `scale=${w}:${h}:force_original_aspect_ratio=increase,crop=${w}:${h}`;
-  // Post-processing, not realtime: spend encode time on quality. CRF 18 +
-  // medium is visually transparent for VJ motion; -r 30 turns the recorder's
-  // variable frame timing into constant 30fps (players and socials want CFR).
-  const args = ['-y', '-i', input, '-vf', vf, '-r', '30',
-    '-c:v', 'libx264', '-preset', 'medium', '-crf', '18', '-pix_fmt', 'yuv420p',
-    '-c:a', 'aac', '-b:a', '256k', '-movflags', '+faststart', output];
+  const args = ['-y', '-i', input];
+  if (opts && opts.srcH264 && opts.srcW === w && opts.srcH === h) {
+    // Source already matches the requested frame and is H.264: REMUX without
+    // re-encoding — the hardware realtime pass stays the only encode in the
+    // final file (zero generational loss).
+    args.push('-c', 'copy');
+  } else {
+    // Rescale/crop needed (e.g. vertical reels) or non-H264 fallback source.
+    // Post-processing, not realtime: spend encode time on quality. -r 60
+    // turns the recorder's variable frame timing into constant fps.
+    const vf = `scale=${w}:${h}:force_original_aspect_ratio=increase,crop=${w}:${h}`;
+    args.push('-vf', vf, '-r', '60',
+      '-c:v', 'libx264', '-preset', 'slow', '-crf', '16', '-pix_fmt', 'yuv420p',
+      '-c:a', 'aac', '-b:a', '256k');
+  }
+  args.push('-movflags', '+faststart', output);
   return new Promise((resolve, reject) => {
     execFile(ffmpegPath(), args, { maxBuffer: 1 << 24 }, (err, stdout, stderr) => {
       if (err) reject(new Error('ffmpeg: ' + String(stderr || err.message).slice(-500)));
diff --git a/src/output.js b/src/output.js
index c2b42a9..2d7a0b0 100644
--- a/src/output.js
+++ b/src/output.js
@@ -181,16 +181,15 @@ async function startRecording(opts) {
     recCanvas.height = canvas.height;
     recCtx = recCanvas.getContext('2d');
     composeFrame();
-    const vstream = recCanvas.captureStream(30);
+    const vstream = recCanvas.captureStream(60);
     const astream = audio.recordDest.stream;
     const stream = new MediaStream([...vstream.getVideoTracks(), ...astream.getAudioTracks()]);
-    // Generous bitrate: this WebM is only an intermediate (deleted after the
-    // MP4 mux) and the realtime VP9 encoder needs headroom on full-screen
-    // abstract motion — 12 Mbps left visible blocking, the ffmpeg pass can
-    // only preserve what survives this first encode.
+    // Generous bitrate: this file is only an intermediate (deleted after the
+    // MP4 mux) — and when no rescale is needed it becomes the FINAL stream
+    // via remux, so the realtime hardware pass is the only encode that counts.
     recorder = new MediaRecorder(stream, {
       mimeType: pickMime(),
-      videoBitsPerSecond: 50e6, // hardware H.264 barely notices; VP9 fallback undershoots anyway
+      videoBitsPerSecond: 80e6, // 1080p60 headroom; the VP9 fallback undershoots anyway
       audioBitsPerSecond: 192e3
     });
     // Serialise chunk delivery: ondataavailable is async, so without a chain the
@@ -203,7 +202,13 @@ async function startRecording(opts) {
     recorder.onstop = async () => {
       stopCompose();
       await chain; // ensure every chunk is flushed, in order, before muxing
-      const res = await djv.recStop(pendingRecOpts || {});
+      // Tell main what the source actually is: same size + H.264 lets it
+      // remux instead of re-encoding (zero extra quality loss).
+      const res = await djv.recStop({
+        ...(pendingRecOpts || {}),
+        srcW: recCanvas.width, srcH: recCanvas.height,
+        srcH264: /avc1|h264/i.test(recorder.mimeType || '')
+      });
       recording = false;
       djv.report({ type: 'recState', recording: false });
       if (res && res.ok) djv.report({ type: 'recSaved', path: res.path, name: res.name, url: res.url });