feat(voice): add iOS VAD runtime support

crates/chanora_audio/src/opus_voice.rs

@@ -0,0 +1,81 @@
+use audiopus::coder::Encoder as OpusEncoder;
+use audiopus::{
+    Application as OpusApp, Bitrate as OpusBitrate, Channels as OpusChannels,
+    SampleRate as OpusSampleRate,
+};
+use std::sync::atomic::{AtomicU32, Ordering};
+use tokio::sync::mpsc;
+use tracing::{info, warn};
+
+use chanora_protocol::{AudioData, CodecType, OutAudio, OutPacket};
+
+use crate::AudioError;
+
+pub(crate) const MAX_OPUS_FRAME: usize = 1275;
+
+const VOIP_BITRATE_BPS: i32 = 32_000;
+const VOIP_COMPLEXITY: u8 = 10;
+const VOIP_PACKET_LOSS_PERC: u8 = 5;
+
+pub(crate) fn new_voip_encoder(context: &str) -> Result<OpusEncoder, AudioError> {
+    let mut encoder = OpusEncoder::new(OpusSampleRate::Hz48000, OpusChannels::Mono, OpusApp::Voip)
+        .map_err(|e| AudioError::Opus(format!("encoder new ({context}): {e}")))?;
+    tune_voip_encoder(&mut encoder, context);
+    Ok(encoder)
+}
+
+pub(crate) fn tune_voip_encoder(encoder: &mut OpusEncoder, context: &str) {
+    if let Err(e) = encoder.set_bitrate(OpusBitrate::BitsPerSecond(VOIP_BITRATE_BPS)) {
+        warn!(target: "chanora_audio", context = %context, error = %e, "opus set_bitrate failed");
+    }
+    if let Err(e) = encoder.set_complexity(VOIP_COMPLEXITY) {
+        warn!(target: "chanora_audio", context = %context, error = %e, "opus set_complexity failed");
+    }
+    if let Err(e) = encoder.set_inband_fec(true) {
+        warn!(target: "chanora_audio", context = %context, error = %e, "opus set_inband_fec failed");
+    }
+    if let Err(e) = encoder.set_packet_loss_perc(VOIP_PACKET_LOSS_PERC) {
+        warn!(
+            target: "chanora_audio",
+            context = %context,
+            error = %e,
+            "opus set_packet_loss_perc failed"
+        );
+    }
+
+    info!(
+        target: "chanora_audio",
+        context = %context,
+        bitrate_bps = VOIP_BITRATE_BPS,
+        complexity = VOIP_COMPLEXITY,
+        inband_fec = true,
+        packet_loss_perc = VOIP_PACKET_LOSS_PERC,
+        "opus encoder tuned for VoIP"
+    );
+}
+
+/// Encode-scope send helper for a freshly encoded Opus voice frame.
+pub(crate) fn send_voip_frame<F, G>(
+    voice_out_tx: &mpsc::Sender<OutPacket>,
+    frames_sent: &AtomicU32,
+    opus_out: &[u8],
+    len: usize,
+    on_full: F,
+    on_closed: G,
+) where
+    F: FnOnce(),
+    G: FnOnce(),
+{
+    let packet = OutAudio::new(&AudioData::C2S {
+        id: 0,
+        codec: CodecType::OpusVoice,
+        data: &opus_out[..len],
+    });
+    match voice_out_tx.try_send(packet) {
+        Ok(()) => {
+            frames_sent.fetch_add(1, Ordering::Relaxed);
+        }
+        Err(mpsc::error::TrySendError::Full(_)) => on_full(),
+        Err(mpsc::error::TrySendError::Closed(_)) => on_closed(),
+    }
+}