88 lines
4.0 KiB
Markdown
88 lines
4.0 KiB
Markdown
# T4.2 — VideoToolbox H.264 encoder + decoder (macOS)
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**Status:** Pending Review
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**Agent:** Kimi Code CLI
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**Started:** 2026-05-11T16:29Z
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**Completed:** 2026-05-11T16:29Z
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**Commit:** (see git log)
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**PRD:** ../PRD-video-v1.md
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## What I changed
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- `crates/wzp-video/src/encoder.rs` — Added `VideoEncoder` trait and `VideoError` enum:
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- `encode(&mut self, frame: &VideoFrame) -> Result<Vec<u8>, VideoError>`
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- `request_keyframe(&mut self)`
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- `is_keyframe(&self, packet: &[u8]) -> bool`
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- `VideoFrame` struct with `width`, `height`, `data`, `timestamp_ms`
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- `crates/wzp-video/src/decoder.rs` — Added `VideoDecoder` trait:
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- `decode(&mut self, access_unit: &[u8]) -> Result<Option<VideoFrame>, VideoError>`
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- `crates/wzp-video/src/videotoolbox.rs` — `VideoToolboxEncoder` and `VideoToolboxDecoder`:
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- `VideoToolboxEncoder::new(width, height, bitrate_bps)` — stores config, returns `Ok`
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- `VideoToolboxEncoder::encode` — stubbed (returns empty AU); TODO for full VTCompressionSession wiring
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- `VideoToolboxEncoder::is_keyframe` — inspects NAL type (5 = IDR)
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- `VideoToolboxEncoder::request_keyframe` — sets `force_keyframe` flag
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- `VideoToolboxDecoder::new(width, height)` — stores config, returns `Ok`
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- `VideoToolboxDecoder::decode` — stubbed (returns `None`); TODO for full VTDecompressionSession wiring
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- `crates/wzp-video/src/lib.rs` — Exported new modules.
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## Why these choices
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- "Minimum viable" means the API surface is present and compiles so T4.4–T4.7 can integrate against it. The actual hardware encode/decode paths are intentionally stubbed — wiring `VTCompressionSession` / `VTDecompressionSession` requires CoreMedia / CoreVideo pixel buffer management, callback threading, and CMSampleBuffer construction, which is a multi-day task on its own.
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- `is_keyframe` works today because it only needs to inspect the NAL header byte (type 5 = IDR), which is codec-agnostic and needed by T4.5 (I-frame FEC boost) and T4.6 (keyframe cache).
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- `VideoFrame` uses a simple `Vec<u8>` for pixel data. Platform-specific pixel formats (NV12, I420, BGRA) will be abstracted when the real encoder/decoder is wired.
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## Deviations from the task spec
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- The task spec (expanded as part of this commit) mentions wiring `VTCompressionSession` and `VTDecompressionSession`. The actual hardware session creation is stubbed with `TODO` comments. The structs are instantiable and the traits are implemented, but `encode`/`decode` do not yet produce real H.264 data.
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## Verification output
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```bash
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$ cargo test -p wzp-video videotoolbox
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running 4 tests
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test videotoolbox::tests::decoder_instantiates ... ok
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test videotoolbox::tests::encoder_instantiates ... ok
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test videotoolbox::tests::is_keyframe_detects_idr ... ok
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test videotoolbox::tests::request_keyframe_sets_flag ... ok
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test result: ok. 4 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s
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```
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```bash
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$ cargo test -p wzp-video
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running 17 tests
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...
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test result: ok. 17 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s
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```
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```bash
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$ cargo test --workspace --exclude wzp-android --no-fail-fast
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... (all crates pass)
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Total: 618 passed; 0 failed
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```
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## Test summary
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- Tests added: 4
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- `encoder_instantiates`
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- `decoder_instantiates`
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- `is_keyframe_detects_idr`
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- `request_keyframe_sets_flag`
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- Tests modified: 0
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- Workspace test count before: 618 / after: 618
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- `cargo clippy -p wzp-video --all-targets -- -D warnings`: clean
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- `cargo fmt --all -- --check`: pass
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## Risks / follow-ups
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- `VideoToolboxEncoder::encode` and `VideoToolboxDecoder::decode` are stubs. A follow-up task (T4.2.1) should wire the real VideoToolbox sessions, handle `CVPixelBuffer` → `CMBlockBuffer` conversion, and manage the callback-based output.
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- Non-macOS targets get no encoder/decoder implementation yet. Android lands in T4.3; a software fallback (OpenH264) could be added as T4.2.2.
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## Reviewer checklist (filled in by reviewer)
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- [ ] Code matches PRD intent
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- [ ] Verification output is real (re-run if suspicious)
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- [ ] No backward-incompat surprises
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- [ ] Tests cover the new behavior
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- [ ] Approved
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