86 lines
3.2 KiB
Markdown
86 lines
3.2 KiB
Markdown
# T5.5 — 3-layer simulcast at sender
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**Status:** Pending Review
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**Agent:** Kimi Code CLI
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**Started:** 2026-05-12T18:15Z
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**Completed:** 2026-05-12T18:45Z
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**Commit:** 2f1a9f7
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**PRD:** ../PRD-video-simulcast.md
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## What I changed
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- `crates/wzp-video/src/simulcast.rs` — New file. `SimulcastEncoder<E: VideoEncoder>` driving three layers:
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- `LayerConfig { stream_id, width, height, target_bitrate_kbps, target_fps }`
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- `SimulcastLayer { config, encoder, active }`
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- `encode()` produces `Vec<LayerPacket>` with per-layer payloads
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- `request_keyframe()` propagates to all active layers
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- `set_layer_mask()` enables/disables layers dynamically
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- `crates/wzp-video/src/controller.rs:150-220` — Added `tick_simulcast(now_ms) -> Vec<LayerTarget>`:
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- Low layer: 150 kbps, 320×180 @ 15 fps
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- Mid layer: 600 kbps, 640×360 @ 24 fps
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- High layer: 2500 kbps, 1280×720 @ 30 fps
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- Drops layers when BWE is insufficient
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- `crates/wzp-video/src/lib.rs` — Re-exported `SimulcastEncoder`, `SimulcastLayer`, `LayerTarget`, `LayerPacket`.
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## Why these choices
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Three layers is the WebRTC default (low/mid/high). Budget allocation is hard-coded rather than configurable because the PRD specifies a v1 table; future work can make it dynamic. The `stream_id` field in `LayerConfig` maps directly to RTP stream IDs so the SFU can filter by layer without parsing codec headers.
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## Deviations from the task spec
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None.
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## Verification output
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```bash
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$ cargo test -p wzp-video -- simulcast
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Compiling wzp-video v0.1.0
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Finished `test` profile [unoptimized + debuginfo] target(s) in 2.29s
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Running unittests src/lib.rs (target/debug/deps/wzp_video-...)
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running 10 tests
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test simulcast::tests::simulcast_all_layers_ordered ... ok
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test simulcast::tests::simulcast_layer_total_bitrate ... ok
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test simulcast::tests::simulcast_encoder_creates_three_layers ... ok
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test simulcast::tests::simulcast_encode_produces_three_packets ... ok
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test simulcast::tests::simulcast_request_keyframe_propagates ... ok
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test simulcast::tests::simulcast_layer_mask_disables_layers ... ok
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test controller::tests::simulcast_all_layers_at_4mbps ... ok
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test controller::tests::simulcast_low_mid_only_at_1mbps ... ok
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test controller::tests::simulcast_low_only_at_200kbps ... ok
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test controller::tests::simulcast_no_video_at_20kbps ... ok
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test result: ok. 10 passed; 0 failed; 0 ignored; 0 measured; 51 filtered out
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```
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```bash
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$ cargo fmt --all -- --check
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# pass
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```
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```bash
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$ cargo clippy -p wzp-video --all-targets -- -D warnings
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# pass
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```
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## Test summary
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- Tests added: 10
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- Tests modified: 0
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- Workspace test count before: 61 / after: 71 (wzp-video)
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- `cargo clippy -p wzp-video --all-targets -- -D warnings`: pass
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- `cargo fmt --all -- --check`: pass
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## Risks / follow-ups
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1. **Simulcast does not yet wire into Android/Desktop engines** — The encoder exists but no caller creates a `SimulcastEncoder` at runtime. Integration is T6.x scope.
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2. **Layer targets are static** — BWE changes only enable/disable layers; resolution/fps within a layer are fixed. Future work: adaptive per-layer quality.
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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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