2 #define _ALSA_INPUT_H 1
4 // ALSA sound input, running in a separate thread and sending audio back
7 // Note: “frame” here generally refers to the ALSA definition of frame,
8 // which is a set of samples, exactly one for each channel. The only exception
9 // is in frame_length, where it means the TIMEBASE length of the buffer
10 // as a whole, since that's what AudioMixer::add_audio() wants.
12 #include <alsa/asoundlib.h>
14 #include <sys/types.h>
22 #include "bmusb/bmusb.h"
28 typedef std::function<bool(const uint8_t *data, unsigned num_samples, bmusb::AudioFormat audio_format, int64_t frame_length, std::chrono::steady_clock::time_point ts)> audio_callback_t;
30 ALSAInput(const char *device, unsigned sample_rate, unsigned num_channels, audio_callback_t audio_callback, ALSAPool *parent_pool, unsigned internal_dev_index);
33 // If not called before start_capture_thread(), the capture thread
34 // will call it until it succeeds.
37 // Not valid before the device has been successfully opened.
38 // NOTE: Might very well be different from the sample rate given to the
39 // constructor, since the card might not support the one you wanted.
40 unsigned get_sample_rate() const { return sample_rate; }
42 void start_capture_thread();
43 void stop_capture_thread();
45 // Set access, sample rate and format parameters on the given ALSA PCM handle.
46 // Returns the computed parameter set and the chosen sample rate. Note that
47 // sample_rate is an in/out parameter; you send in the desired rate,
48 // and ALSA picks one as close to that as possible.
49 static bool set_base_params(const char *device_name, snd_pcm_t *pcm_handle, snd_pcm_hw_params_t *hw_params, unsigned *sample_rate);
52 void capture_thread_func();
53 int64_t frames_to_pts(uint64_t n) const;
55 enum class CaptureEndReason {
60 CaptureEndReason do_capture();
63 unsigned sample_rate, num_channels, num_periods;
64 snd_pcm_uframes_t period_size;
65 snd_pcm_uframes_t buffer_frames;
66 bmusb::AudioFormat audio_format;
67 audio_callback_t audio_callback;
69 snd_pcm_t *pcm_handle = nullptr;
70 std::thread capture_thread;
71 std::atomic<bool> should_quit{false};
72 std::unique_ptr<uint8_t[]> buffer;
73 ALSAPool *parent_pool;
74 unsigned internal_dev_index;
77 #endif // !defined(_ALSA_INPUT_H)