+ AudioDevice *find_audio_device(DeviceSpec device_spec);
+
+ void find_sample_src_from_device(const std::vector<float> *samples_card, DeviceSpec device_spec, int source_channel, const float **srcptr, unsigned *stride);
+ void fill_audio_bus(const std::vector<float> *samples_card, const InputMapping::Bus &bus, unsigned num_samples, float *output);
+ void reset_device_mutex_held(DeviceSpec device_spec);
+
+ unsigned num_cards;
+
+ mutable std::mutex audio_mutex;
+
+ AudioDevice cards[MAX_CARDS]; // Under audio_mutex.