69 lines
2.5 KiB
Markdown
69 lines
2.5 KiB
Markdown
# T2.3 — Plumb BWE into `AdaptiveQualityController`
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**Status:** Pending Review
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**Agent:** Kimi Code CLI
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**Started:** 2026-05-11T17:13Z
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**Completed:** 2026-05-11T17:20Z
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**Commit:** 846c98e
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**PRD:** ../PRD-transport-feedback-bwe.md
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## What I changed
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- `crates/wzp-proto/src/quality.rs` — `AdaptiveQualityController`:
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- Added `bwe: Option<Arc<BandwidthEstimator>>` field.
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- Added `set_bandwidth_estimator(&mut self, bwe: Arc<BandwidthEstimator>)` setter.
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- Added `tier_ceiling_bps(tier: Tier) -> u64` helper using `QualityProfile::total_bitrate_kbps()`.
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- In `try_transition()`, before upgrading to a higher tier, check BWE headroom:
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```rust
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if let Some(ref bwe) = self.bwe {
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let required = (Self::tier_ceiling_bps(next_tier) * 130) / 100;
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if bwe.target_send_bps() < required {
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self.consecutive_up = 0;
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return None;
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}
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}
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```
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This requires `target_send_bps() >= 130%` of the next tier's bitrate ceiling (including FEC overhead).
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## Why these choices
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The 130% headroom factor is a safety margin: we only upgrade if the bandwidth estimate comfortably exceeds the target tier's requirement, preventing flapping when BWE is borderline. Resetting `consecutive_up` to 0 on BWE block gives the estimator time to converge before the next upgrade attempt.
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Checking the *next* tier's ceiling (not the current tier) is correct: the guard answers "can we afford the tier we're trying to move into?"
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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-proto quality
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running 24 tests
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...(all 24 pass)...
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test result: ok. 24 passed; 0 failed; 0 ignored; 0 measured; 95 filtered out; finished in 0.10s
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```
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## Test summary
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- Tests added: 1
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- `bwe_guard_blocks_upgrade_when_bandwidth_insufficient` — verifies low BWE blocks upgrade, high BWE allows it after counter reset
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- Tests modified: 0
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- `wzp-proto` test count: 119 (was 118 before T2.3)
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- `cargo clippy -p wzp-proto --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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- `BandwidthEstimator` is attached via `set_bandwidth_estimator()`; call sites in `wzp-client` (send/recv loops) will create and wire it in a future task.
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- The BWE guard only applies to upgrades. Downgrades are unchanged — they react quickly to quality reports regardless of BWE.
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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
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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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