fix(ios,audio): pair VPIO with AVAudioSession mode .voiceChat (rc.8+67)

User report at +66: capture (mic -> remote) is clean, but local
playback (remote -> speaker) is 'broken and poor', particularly
for human voice. Musicbot audio (loud, near-continuous) plays
correctly; human voice (peaks ~-6 dB, average ~-40 dB, classic
20 dB peak-to-average ratio) sounds gated out so most inter-
phoneme content is unintelligible.

Diagnostic at +66 (render callback peak sampling every 100
callbacks during a 60-second talker session) showed peak_stereo
values in the 0.005-0.01 range with occasional 0.13-0.49 spikes
\u2014 i.e. the signal is REAL and reaching the device, but VPIO's
output-side voice processing chain is gating the average-level
content.

Root cause: AVAudioSession mode .default + VPIO is a mismatched
pairing. Under .default mode the VPIO unit's internal AGC/NS
thresholds are tuned wrong for telephony-style speech and treat
quiet inter-phoneme content as noise to gate out.

Fix: switch back to mode .voiceChat which is Apple's documented
pair for VoiceProcessingIO. WebRTC's reference iOS audio device
manager (chromium googlesource voice_processing_audio_unit.mm)
also uses this pair. VPIO under .voiceChat tunes its processing
chain for speech and passes quiet content through cleanly.

The original 'speaker/receiver toggle is silent under .voiceChat'
bug was caused by cpal's RemoteIO unit binding to a stale
physical transducer at construction time, not by .voiceChat
itself. After migrating to VPIO at commits 1-4 (af686ca through
e7c3ffa) the route binding is correct under either mode because
VPIO natively re-binds on overrideOutputAudioPort \u2014 it IS the
canonical voice unit. So .default lost its only benefit and we
revert to the Apple-documented pairing.

Category options unchanged: .allowBluetoothHFP +
.allowBluetoothA2DP \u2014 BT headsets still permitted in both
directions regardless of mode.

Build counter 66 -> 67.

This commit is contained in:

EdisonJwa

2026-05-17 01:44:05 +08:00

parent 63cbab901e

commit c89acacc74

2 changed files with 32 additions and 27 deletions

									
										apps/chanora_flutter/pubspec.yaml
									
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				@@ -16,7 +16,7 @@ publish_to: 'none' # Remove this line if you wish to publish to pub.dev

				# https://developer.apple.com/library/archive/documentation/General/Reference/InfoPlistKeyReference/Articles/CoreFoundationKeys.html

				# In Windows, build-name is used as the major, minor, and patch parts

				# of the product and file versions while build-number is used as the build suffix.

				version: 1.0.0-rc.8+66

				version: 1.0.0-rc.8+67

				environment:

				  sdk: ^3.11.5