# M11-09 Status

status: done
task: runtime codec probes for IMAGE, SOUND, and MOVIE strips
updated: 2026-08-17 America/New_York

## Scope

Schema 1 codec probe requests and receipts bind the Sequencer strip family, canonical
MIME type, source byte length, and source SHA-256. File names and source paths are not
accepted by the probe contract, so extensions cannot grant capability. A READY receipt
must also use the family-specific backend and carry validated decoded dimensions or
audio frame metadata.

The production browser probe hashes the supplied bytes and performs a real decode:
`createImageBitmap` for IMAGE, a fixed 48 kHz `OfflineAudioContext` for SOUND, and a
muted `HTMLMediaElement` load/seek/canvas readback for MOVIE. The committed movie is a
deterministic 16x16, two-frame H.264 MP4 generated locally by FFmpeg. This task does not
claim frame-accurate WebCodecs seeking, waveform/proxy generation, A/V synchronization,
arbitrary codec support, or final encoding.

## Evidence

- `WEB_TEST_PORT=5570 npm --prefix web run test:sequencer-codec-probe`: unit 3/3 and
  Chromium 1/1 passed. PNG, WAV, and H.264 MP4 returned READY with their expected
  runtime backend and decoded metadata.
- Deliberately wrong file extensions had no effect. Corrupt bytes, source identity
  drift, PNG bytes declared as MOVIE, a forged backend, and a forged receipt all stayed
  BLOCKED with `SEQUENCER_CODEC_UNSUPPORTED` at the gate.
- The first Chromium attempt failed before business execution because `/protocol` is
  not exposed by Vite; the test now imports the existing app adapter. The second decoded
  all media but exposed device-rate Web Audio resampling; the production probe now uses
  a fixed 48 kHz OfflineAudioContext. The complete command was then rerun successfully.
- Sequencer Main reader, N-021 browser regression, and the one-million-frame long media
  performance/restart test passed. Full regression passed: typecheck, lint, Node suite,
  production build, status consistency, release evidence validation, and
  `git diff --check`.

## Rollback

Remove the codec probe protocol/runtime/tests/movie fixture, restore the MIME-set gate,
restore M11 to 8/14, and remove the new N-021 completed slice. Keep the V1 long-media
IMAGE/SOUND index/cache behavior and all M11-08 compositor behavior unchanged.