feat(portal): independent WebRTC thread + channel tuning for 60fps mouse latency

- Move WebRTC send to dedicated wl-webrtc-webrtc thread (was inline in main loop)
- Reduce frame_rx 16→1, input_tx 2→1 (drop-on-full), webrtc_tx 32→2
- Recv_timeout 10ms→2ms to reduce pipeline latency
- Fix sent_gap_p95 stats bug: compute gap at actual send time in WebRTC
  thread instead of batch-draining at snapshot time (was always 0.0ms)
- High profile via AVCodecContext.profile, veryfast preset, 5x bitrate
- Stats drain via sent_gap channel with record_send_from_thread()
- Shutdown: drop input_tx → join encode → drop webrtc_tx → join webrtc

src/state_portal.rs

@@ -33,6 +33,11 @@ struct EncodeThread {
     timing_rx: crossbeam_channel::Receiver<EncodeThreadTiming>,
 }
 
+struct WebrtcThread {
+    handle: Option<std::thread::JoinHandle<()>>,
+    sent_gap_rx: crossbeam_channel::Receiver<f64>,
+}
+
 /// 门户模式的主状态机
 ///
 /// 负责管理从 PipeWire 采集屏幕帧、通过 VAAPI 硬件编码的完整生命周期。
@@ -50,9 +55,8 @@ pub struct StatePortal {
     start_time: Option<Instant>,                    // 编码开始时间
     stats: PipelineStats,                           // 管道统计（窗口化帧计时 + 每秒快照）
     pw_dropped_prev: u64,                           // 上一窗口的 PipeWire 丢弃帧数（用于增量计算）
-    webrtc: Option<WebRtcState>,                    // WebRTC 状态（仅 WebRTC 模式启用）
-    webrtc_rx: Option<crossbeam_channel::Receiver<Vec<u8>>>,
-    webrtc_frames_sent: u64,
+    webrtc: Option<WebRtcState>,
+    webrtc_thread: Option<WebrtcThread>,
     webrtc_paused: Option<Arc<AtomicBool>>,
     last_capture_arrival: Option<Instant>,  // timestamp of last real frame arrival
     stall_start: Option<Instant>,           // when current stall began
@@ -98,8 +102,7 @@ impl StatePortal {
             stats: PipelineStats::new(),
             pw_dropped_prev: 0,
             webrtc,
-            webrtc_rx: None,
-            webrtc_frames_sent: 0,
+            webrtc_thread: None,
             webrtc_paused,
             last_capture_arrival: None,
             stall_start: None,
@@ -112,14 +115,10 @@ impl StatePortal {
 
     /// 轮询 PipeWire 事件并编码帧
     ///
-    /// `block=true` 时使用 recv_timeout 阻塞等待帧（最多 10ms），
+    /// `block=true` 时使用 recv_timeout 阻塞等待帧（最多 2ms），
     /// `block=false` 时使用 try_recv 非阻塞检查。
     /// 返回 `Ok(true)` 表示已处理事件，`Ok(false)` 表示暂无数据。
     pub fn poll_and_encode(&mut self, block: bool) -> Result<bool> {
-        // 先处理 WebRTC 信令、网络轮询，并转发已编码帧
-        // WebRTC: process signaling, network, and forward encoded frames
-        self.poll_webrtc()?;
-
         // 检查 PipeWire 控制事件（流结束 / 错误）
         if let Ok(ctrl) = self.cap.event_receiver().try_recv() {
             match ctrl {
@@ -147,8 +146,8 @@ impl StatePortal {
 
         // 根据阻塞模式选择不同的帧接收策略
         let frame = if block {
-            // 阻塞模式：最多等待 10ms 接收帧
-            match self.cap.frame_receiver().recv_timeout(std::time::Duration::from_millis(10)) {
+            // 阻塞模式：最多等待 2ms 接收帧
+            match self.cap.frame_receiver().recv_timeout(std::time::Duration::from_millis(2)) {
                 Ok(frame) => frame,
                 Err(_) => {
                     self.record_capture_timeout();
@@ -193,7 +192,7 @@ impl StatePortal {
                 );
                 // 码率：未指定时按分辨率 × 帧率动态计算
                 let actual_bitrate = self.args.bitrate.unwrap_or_else(|| {
-                    2 * (enc_width as u64) * (enc_height as u64) * (self.args.fps as u64) / 100
+                    5 * (enc_width as u64) * (enc_height as u64) * (self.args.fps as u64) / 100
                 });
                 // GOP 大小：WebRTC 模式使用更小的 GOP（fps/2，最低10），MP4 模式使用 fps
                 let actual_gop_size = self.args.gop_size.unwrap_or_else(|| {
@@ -216,8 +215,8 @@ impl StatePortal {
                         enc_height,
                         self.args.fps,
                     )?;
-                    let (webrtc_tx, webrtc_rx) = crossbeam_channel::bounded(32);
-                    let (input_tx, input_rx) = crossbeam_channel::bounded::<CpuNv12Frame>(2);
+                    let (webrtc_tx, webrtc_rx) = crossbeam_channel::bounded(2);
+                    let (input_tx, input_rx) = crossbeam_channel::bounded::<CpuNv12Frame>(1);
                     let (timing_tx, timing_rx) = crossbeam_channel::bounded::<EncodeThreadTiming>(32);
                     let encode = SwEncEncode::new_webrtc(
                         enc_width,
@@ -233,7 +232,18 @@ impl StatePortal {
                         .spawn(move || encode_thread_loop(encode, input_rx, timing_tx))?;
                     self.enc_import = Some(import);
                     self.enc_thread = Some(EncodeThread { handle: Some(handle), input_tx, timing_rx });
-                    self.webrtc_rx = Some(webrtc_rx);
+
+                    let wrtc = self.webrtc.take()
+                        .ok_or_else(|| anyhow::anyhow!("internal: WebRtcState missing during init"))?;
+                    let paused = self.webrtc_paused.as_ref()
+                        .ok_or_else(|| anyhow::anyhow!("internal: webrtc_paused missing"))?
+                        .clone();
+                    let fps = self.args.fps;
+                    let (sent_gap_tx, sent_gap_rx) = crossbeam_channel::bounded(64);
+                    let webrtc_handle = std::thread::Builder::new()
+                        .name("wl-webrtc-webrtc".into())
+                        .spawn(move || webrtc_thread_loop(wrtc, webrtc_rx, fps, paused, sent_gap_tx))?;
+                    self.webrtc_thread = Some(WebrtcThread { handle: Some(webrtc_handle), sent_gap_rx });
                 } else {
                     // MP4 模式：编码输出写入文件
                     let output_path = self.args.output.as_deref()
@@ -265,16 +275,24 @@ impl StatePortal {
             }
         }
 
-        // 在返回前再次轮询 WebRTC，确保本帧编码后的数据及时转发
-        // WebRTC: drain encoded frames produced by this poll before returning.
-        self.poll_webrtc()?;
-
         // 每秒输出一次结构化管道统计（仅 --stats 启用时记录日志）
         if self.args.stats && self.stats.should_snapshot() {
-            // PipeWire 丢弃帧数：CapPortal 尚未暴露 dropped_count()，暂用占位
             self.stats.set_pipewire_dropped(0, 0);
-            let enc_q = self.webrtc_rx.as_ref().map(|r| r.len()).unwrap_or(0);
-            self.stats.set_queue_depths(0, enc_q);
+            self.stats.set_queue_depths(0, 0);
+            if let Some(ref enc_thread) = self.enc_thread {
+                while let Ok(timing) = enc_thread.timing_rx.try_recv() {
+                    self.stats.record_encode_thread(
+                        timing.sws_us,
+                        timing.encode_us,
+                        timing.output_bytes,
+                    );
+                }
+            }
+            if let Some(ref webrtc_thread) = self.webrtc_thread {
+                while let Ok(gap_ms) = webrtc_thread.sent_gap_rx.try_recv() {
+                    self.stats.record_send_from_thread(gap_ms);
+                }
+            }
             let snap = self.stats.snapshot_and_reset();
             if self.filler_frames_sent > 0 {
                 tracing::info!("stats: {snap} filler_frames_sent={}", self.filler_frames_sent);
@@ -316,7 +334,7 @@ impl StatePortal {
     }
 
     fn maybe_send_filler_frame(&mut self) {
-        if self.webrtc.is_none() || self.stall_start.is_none() {
+        if self.webrtc_thread.is_none() || self.stall_start.is_none() {
             return;
         }
         let Some(cached) = &self.last_fillable_frame else {
@@ -509,8 +527,8 @@ impl StatePortal {
                     self.frames_encoded += 1;
                     self.last_fillable_frame = Some(fillable_frame);
                 }
-                Err(crossbeam_channel::TrySendError::Full(_frame)) => {
-                    tracing::warn!("Encode thread input full, dropping portal frame");
+                Err(crossbeam_channel::TrySendError::Full(_)) => {
+                    tracing::debug!("Encode thread input full, dropping portal frame");
                 }
                 Err(crossbeam_channel::TrySendError::Disconnected(_frame)) => {
                     tracing::error!("Encode thread input disconnected");
@@ -529,9 +547,7 @@ impl StatePortal {
     /// 使用 `enc.take()` 确保编码器只被 flush 一次，即使多次调用也安全（幂等）。
     pub fn shutdown(&mut self) {
         self.last_fillable_frame = None;
-        // 先 drop receiver，使 flush() 中的 try_send() 立即返回 Disconnected
-        // 而非在满通道上阻塞（修复 issue #8 死锁）
-        self.webrtc_rx = None;
+        // 1. Stop encode thread (drops webrtc_tx → signals WebRTC thread to exit)
         if let Some(mut enc_thread) = self.enc_thread.take() {
             drop(enc_thread.input_tx);
             if let Some(handle) = enc_thread.handle.take() {
@@ -541,6 +557,15 @@ impl StatePortal {
             }
         }
         self.enc_import = None;
+        // 2. Wait for WebRTC thread (exits when webrtc_tx is dropped by encode thread)
+        if let Some(mut webrtc_thread) = self.webrtc_thread.take() {
+            if let Some(handle) = webrtc_thread.handle.take() {
+                if handle.join().is_err() {
+                    tracing::error!("WebRTC thread panicked during shutdown");
+                }
+            }
+        }
+        // 3. Flush MP4 encoder if present
         if let Some(mut enc) = self.enc.take() {
             if let Err(e) = enc.flush() {
                 tracing::error!("Flush error during shutdown: {e}");
@@ -565,60 +590,6 @@ impl StatePortal {
     pub fn is_errored(&self) -> bool {
         self.errored
     }
-
-    /// 轮询 WebRTC 信令通道并转发编码帧
-    ///
-    /// 处理信令交换、网络轮询，以及从编码通道中取出已编码的 H.264 数据
-    /// 并通过 WebRTC 发送。
-    fn poll_webrtc(&mut self) -> Result<()> {
-        let Some(ref mut wrtc) = self.webrtc else { return Ok(()) };
-
-        wrtc.handle_signaling()?;
-        wrtc.poll_and_feed()?;
-
-        let connected = wrtc.is_connected();
-
-        if let Some(ref paused) = self.webrtc_paused {
-            let was_paused = paused.load(Ordering::Relaxed);
-            let now_paused = !connected;
-            if was_paused && !now_paused {
-                tracing::info!("WebRTC client connected, resuming encoding");
-            } else if !was_paused && now_paused {
-                tracing::warn!("WebRTC client disconnected, pausing encoding");
-            }
-            paused.store(now_paused, Ordering::Relaxed);
-        }
-
-        if let Some(ref rx) = self.webrtc_rx {
-            let mut count = 0u32;
-            while let Ok(data) = rx.try_recv() {
-                if !connected {
-                    continue;
-                }
-                count += 1;
-                if let Err(e) = wrtc.write_h264_frame(&data, self.webrtc_frames_sent, self.args.fps) {
-                    tracing::debug!("WebRTC write frame error: {e}");
-                }
-                self.stats.record_send(0.0, None);
-                self.webrtc_frames_sent = self.webrtc_frames_sent.saturating_add(1);
-            }
-            if count > 0 {
-                tracing::debug!("WebRTC forwarded {count} frames from channel");
-            }
-        }
-
-        if let Some(ref enc_thread) = self.enc_thread {
-            while let Ok(timing) = enc_thread.timing_rx.try_recv() {
-                self.stats.record_encode_thread(
-                    timing.sws_us,
-                    timing.encode_us,
-                    timing.output_bytes,
-                );
-            }
-        }
-
-        Ok(())
-    }
 }
 
 fn encode_thread_loop(
@@ -657,6 +628,78 @@ fn encode_thread_loop(
     tracing::info!("Encode thread exiting");
 }
 
+fn webrtc_thread_loop(
+    mut wrtc: WebRtcState,
+    webrtc_rx: crossbeam_channel::Receiver<Vec<u8>>,
+    fps: u32,
+    paused: Arc<AtomicBool>,
+    sent_gap_tx: crossbeam_channel::Sender<f64>,
+) {
+    let mut frames_sent: u64 = 0;
+    let mut last_send: Option<std::time::Instant> = None;
+    let timeout = Duration::from_millis(1);
+
+    loop {
+        if let Err(e) = wrtc.handle_signaling() {
+            tracing::error!("WebRTC signaling error: {e}");
+            break;
+        }
+        if let Err(e) = wrtc.poll_and_feed() {
+            tracing::error!("WebRTC poll error: {e}");
+            break;
+        }
+
+        let connected = wrtc.is_connected();
+        let was_paused = paused.load(Ordering::Relaxed);
+        let now_paused = !connected;
+        if was_paused && !now_paused {
+            tracing::info!("WebRTC client connected, resuming encoding");
+        } else if !was_paused && now_paused {
+            tracing::warn!("WebRTC client disconnected, pausing encoding");
+        }
+        paused.store(now_paused, Ordering::Relaxed);
+
+        if connected {
+            while let Ok(data) = webrtc_rx.try_recv() {
+                if let Err(e) = wrtc.write_h264_frame(&data, frames_sent, fps) {
+                    tracing::debug!("WebRTC write frame error: {e}");
+                }
+                frames_sent = frames_sent.saturating_add(1);
+                let gap_ms = last_send
+                    .map(|l| l.elapsed().as_secs_f64() * 1000.0)
+                    .unwrap_or(0.0);
+                last_send = Some(std::time::Instant::now());
+                let _ = sent_gap_tx.try_send(gap_ms);
+            }
+        } else {
+            while webrtc_rx.try_recv().is_ok() {}
+        }
+
+        match webrtc_rx.recv_timeout(timeout) {
+            Ok(data) => {
+                if wrtc.is_connected() {
+                    if let Err(e) = wrtc.write_h264_frame(&data, frames_sent, fps) {
+                        tracing::debug!("WebRTC write frame error: {e}");
+                    }
+                    frames_sent = frames_sent.saturating_add(1);
+                    let gap_ms = last_send
+                        .map(|l| l.elapsed().as_secs_f64() * 1000.0)
+                        .unwrap_or(0.0);
+                    last_send = Some(std::time::Instant::now());
+                    let _ = sent_gap_tx.try_send(gap_ms);
+                }
+            }
+            Err(crossbeam_channel::RecvTimeoutError::Timeout) => {}
+            Err(crossbeam_channel::RecvTimeoutError::Disconnected) => {
+                tracing::info!("WebRTC channel disconnected, exiting thread");
+                return;
+            }
+        }
+    }
+
+    tracing::info!("WebRTC thread exiting");
+}
+
 impl Drop for StatePortal {
     // 析构时自动调用 shutdown，确保编码器被刷新、资源被释放
     fn drop(&mut self) {