Root cause (revisited): the previous gate paused proc.stdout when vPipe was
full. That stalled the SAME ffmpeg process that also writes audio on fd3, so
audio stuttered; and the ~8s backlog already built never drained → permanent
lag. Symptom: 'video still lags bad, now audio also choppy'.
Fix:
- spawn demuxer ffmpeg with -re for stream (pipe) input. Verified locally:
a 5s NUT clip demuxes in 0.088s without -re (57x burst) vs 4.539s with -re
(real-time). -re throttles the input read, which back-pressures the whole
upstream chain (encoder x264 -> merge ffmpeg -> yt-dlp) through OS pipes,
pinning production at 1x. No unbounded backlog.
- drop oldest queued frame when vPipe readableLength >= 30 (transient sender
stall guard) instead of pausing stdout — keeps video fresh and audio intact.
- removed gateSource/sourcePaused entirely.
Audio and video now pace together at 1x; video is the newest frame, not an
8-second-old one.
asepharyana
6e7c4901c9