feat: backpressure — the pipeline slows instead of losing frames

Browse Source

Picks up the KPN fix: node data outputs block on a full channel rather than
dropping. Sentinels stay out-of-band, so EOF can always overtake a stalled data
path and the hold-and-wait deadlock that comment warns about is not reachable.

Verified on a 77s clip at 5 fps, which should yield 385 sampled frames:

  before  65 written, 320 dropped, 29s, two runs differ
  after   385 written, 0 dropped, 17s, two runs byte-identical

The determinism is the part that matters. Golden fixtures were impossible while
what got dropped depended on timing; VR-001 fixture generation is unblocked by
this, and so is the CI replay strategy that depends on it.

Faster rather than slower, which is worth recording because the intuition runs
the other way: a dropped frame has already cost its decode, and the overflow
exception cost more still.

AR-004 is not fully closed. Channel capacity remains a count of items, while a
face carries a 112x112 crop and a 512-float embedding — so a crowded frame
occupies far more memory per slot than a sparse one. Bounding by bytes in
flight is the remaining half, and it matters once max_faces is removed (AR-003).

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

TRACES: AR-004, VR-001 | SR-002

...

This commit is contained in:

dtourolle

2026-07-31 10:35:29 +02:00

co-authored by Claude Opus 5

parent b98372bad8

commit 09a4650fd9

3 changed files with 15 additions and 4 deletions

Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL

Download Patch File Download Diff File Expand all files Collapse all files

external/KPN

Vendored

+1 -1

Submodule external/KPN updated: 4b6e498ba7...be6e92268c