The Apple client on a loudspeaker was the primary reported echo source:
two AVAudioEngines by design (arbitrary mic/speaker pairs, two clocks)
meant no unit ever saw render and capture together, which is exactly
what setVoiceProcessingEnabled needs. With the mic enabled and the new
"Echo cancellation" toggle on (both defaults), playback and capture now
share ONE engine with the system voice processor engaged — AEC, noise
suppression and AGC — and the input node's other-audio ducking pinned
to .min with advanced ducking off, because this is a game stream, not a
call: the host's audio must never dip under the outgoing voice.
The two-engine path survives where it is the right answer: echo cancel
off, macOS sessions with a hand-picked speaker/mic UID or input channel
(the voice processor only follows the system default devices, and its
capture side is its own mono mix — a per-channel pick can't survive
it), and any machine whose voice processor refuses to engage. Every
failure falls back to a working configuration rather than silence. The
capture chain reads the input format after the processor is enabled,
so its mono/lower-rate output flows through the existing converter
unchanged; a first-run permission grant swaps the playback-only engine
for the combined one in place, reusing the same jitter ring and drain
thread; background mic muting mutes the processor's input instead of
pausing the shared engine (playback keeps running).
echo_cancel rides the full settings plumbing micEnabled has — defaults
key, effective settings, profile overlay (serialized as `echo_cancel`;
the Rust catalog carries it via unknown-key passthrough until it grows
the field), a captioned toggle beside the Microphone row, and a gamepad
settings row. tvOS behavior is untouched (playback only, as before).
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
enricobuehlerandClaude Fable 5
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