User report: 'sound heard are too poor' on iPhone iOS \u2014 garbled/
robotic + stutters/dropouts.
The Opus encoder ran with audiopus defaults: 'auto' bitrate that
drops to ~6 kbps during silence (sounds watery on speech resume),
inband FEC disabled (single packet loss = silent gap), no packet-
loss percentage hint (encoder can't budget bits for redundancy).
On lossy mobile networks (cell, WiFi roaming) this combination
sounds noticeably worse than the same Opus stream from a desktop
client. Garbled = silence-bitrate transitions; stutters = packet
loss without FEC.
Fix: tune the encoder once at construction with values derived
from RFC 6716 \u00a77.1 (Opus VoIP recommendations), Discord's voice
client tuning, and the Mumble defaults.
* set_bitrate(32_000) \u2014 sweet spot for mono speech. Below
24 kbps starts to sound watery;
above 64 kbps wastes bandwidth.
Discord uses 64 kbps; Mumble
defaults to 40 kbps; we pick
32 kbps as a conservative VoIP
value that survives ~100 kbps
uplinks comfortably.
* set_complexity(10) \u2014 max quality. The CPU cost on a
modern iPhone (A14+) or any
desktop is negligible (~0.5 % of
a single core for 48 kHz mono).
* set_inband_fec(true) \u2014 Opus inserts a low-bitrate copy
of the previous frame inside the
current packet so single-packet
loss can be reconstructed from
the next packet. Essential on
lossy mobile. The decoder side
(tsclientlib's AudioHandler)
auto-handles FEC frames; no
receiver-side change needed.
* set_packet_loss_perc(5) \u2014 tells the encoder to budget
bits for 5 % expected loss.
Higher values trade audio
quality for resilience.
Each setter is wrapped in a soft-fail: if an exotic libopus build
rejects one of these, we log + continue with the still-functional
encoder rather than aborting the audio engine. info!-log a one-
liner per-engine-start summarising the tuned values so a future
diagnostic export can correlate audio reports with the active
configuration.
Application::Voip mode was already set (engine.rs:630, unchanged);
the new calls layer on top of that mode's defaults.
cargo test -p chanora_audio --release --lib: 32 passed.
flutter build ios --release --no-codesign: 17.2 s, Runner.app
30.4 MB.
EdisonJwa
54ec8dd5a8