[feat] receive remote audio with panel playback and bounded WAV capture

libs/controller/src/controller_audio.cpp

@@ -0,0 +1,49 @@
+#include "controller_session.h"
+
+#include <stream_names.h>
+#include <string_view>
+
+namespace crossdesk {
+void ControllerSession::Audio(const char *data, size_t size, const char *, size_t,
+                              const char *stream, size_t stream_size, void *opaque) {
+  // MiniRTC's receive decoder produces 48 kHz, mono, signed 16-bit PCM.
+  auto &session = *static_cast<ControllerSession *>(opaque);
+  if (!data || !size || size > 11520 || (size & 1) || !stream ||
+      std::string_view(stream, stream_size) != kAudioStream) return;
+  std::lock_guard lock(session.mutex_);
+  if (session.stopping_ || !session.audio_enabled_) return;
+  while (!session.audio_frames_.empty() && session.audio_bytes_ + size > 96000) {
+    session.audio_bytes_ -= session.audio_frames_.front().pcm.size();
+    session.audio_frames_.pop_front();
+    ++session.audio_dropped_;
+  }
+  AudioFrame frame;
+  frame.generation = session.callback_generation_;
+  frame.sequence = ++session.audio_sequence_;
+  frame.pcm.assign(data, data + size);
+  session.audio_bytes_ += size;
+  session.audio_frames_.push_back(std::move(frame));
+}
+void ControllerSession::SetAudio(bool enabled) {
+  if (!Connected()) throw std::invalid_argument("NOT_CONNECTED");
+  {
+    std::lock_guard lock(mutex_);
+    audio_enabled_ = enabled;
+    audio_frames_.clear();
+    audio_bytes_ = 0;
+  }
+  RemoteAction action{};
+  action.type = audio_capture;
+  action.a = enabled;
+  Send(kControlStream, action.to_json());
+  Preview();
+}
+std::optional<AudioFrame> ControllerSession::TakeAudio() {
+  std::lock_guard lock(mutex_);
+  if (audio_frames_.empty()) return std::nullopt;
+  auto frame = std::move(audio_frames_.front());
+  audio_frames_.pop_front();
+  audio_bytes_ -= frame.pcm.size();
+  return frame;
+}
+} // namespace crossdesk