Root causes found for the 4K stalls and the second-footage memory
blowup (audit + code review):
- ticket bookkeeping leaked unbounded: the procpool ticket table and
the arena slot map only ever grew (50-100 tickets/sec during
playback, each pinning montage params and shm region views).
Completed/cancelled/superseded/crashed entries are now removed, and
the arena reaps fire-and-forget tickets once finished; the sync poll
path reaps via a terminal result() read. InFlight duplicate submits
now answer State immediately instead of sitting in the map forever.
- decode ran a full-resolution swscale to F32 RGBA (~132 MB at 4K)
plus a second full-res copy before downscaling to the 480px proxy:
RetrieveVideoParams.target_size lets swscale convert AND resize in
one pass (bilinear, matching the old Rust resampler), so a 4K
preview frame costs ~1 MB instead of ~260 MB of churn. This applies
to proxy AND full-res requests alike.
- per-process decoder cache was unbounded (each session pins an FFmpeg
context + 2 native decoded frames): LRU-capped at 16, eviction drops
the map entry (in-flight renders keep their Arc; Drop releases
FFmpeg).
- playback window completions were not generation-gated: a stale
render from before an edit landed in the rebuilt window (wrong frame
displayed, fresh request blocked). Stale completions now return
their shm slot credit instead.
- async audio prefetch used the polling ticket submit without ever
polling: switched to the fire-and-forget submit so entries reap.
Mike-Solar
fa3951344b