forked from unom/punktfunk
enricobuehlerandClaude Fable 5
e54258b8ac
The capture path carried three latencies that had nothing to do with the network: a 2048-frame tap request (42.7 ms bursts before the first sample could even be sliced), 20 ms Opus framing, and a mono signal duplicated into both stereo channels because the encoder was configured like the downlink. CoreAudio's Opus encoder takes mFramesPerPacket=480 and mChannelsPerFrame=1 just fine — probed empirically: the converter truly emits 10 ms mono CELT packets (TOC config 30), one per 480-frame chunk, and the stereo-shaped decoder upmixes them with the tone intact — so the uplink now asks for 10 ms tap buffers and encodes 48 kbps mono 10 ms packets, with 960 kept only as an init-time fallback. The host decodes any Opus frame ≤120 ms, so nothing changes on the wire's far end. The tap thread also stops burning cycles per callback: the mono fold and resampler scratch buffers are allocated once (regrown only if a larger device quantum ever arrives), and the chunk slicer walks a head index instead of removeFirst — which memmoved the entire backlog for every packet on a render-adjacent thread. iOS additionally asks the session for 5 ms IO quanta at 48 kHz when the mic is on (best-effort; the hardware decides). Verified: swift build (macOS arm64), swift test OpusCodecTests + AudioChannelFoldTests, and an iOS arm64 cross-build; the 480/mono behavior confirmed by TOC inspection on macOS 15. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>