std::map<int, PendingFrame> pending_video_frames; // under frame_queue_mutex
std::map<int64_t, std::vector<float>> pending_audio_frames; // under frame_queue_mutex
QSurface *surface;
std::map<int, PendingFrame> pending_video_frames; // under frame_queue_mutex
std::map<int64_t, std::vector<float>> pending_audio_frames; // under frame_queue_mutex
QSurface *surface;