libsoundio Documentation

libsoundio is a C library designed for high-performance, cross-platform audio I/O.

Key Capabilities:

• Device Access: Supports both raw devices (best performance, exclusive access) and shared devices (default, provides sample rate/format conversion).
• Identification: Provides both id (persistent across plug/unplug events, good for config files) and friendly name (for user display).
• Backend Optimization: Automatically handles backend-specific requirements like fixed buffer sizes (JACK/CoreAudio) vs. direct buffer management (ALSA/PulseAudio/WASAPI).
• Event Monitoring: Can monitor device changes and backend disconnections (e.g., JACK/PulseAudio server shutdown).
• Channel Layouts: Full support for channel maps/layouts for surround sound.
• Multi-Backend: Ability to connect to multiple backends simultaneously (e.g., ALSA and JACK at once).
• Low Overhead: No dependency on libstdc++, no exceptions, no RTTI, and no setjmp.

This example demonstrates how to initialize libsoundio, connect to the default output device, and use a write callback to generate a sine wave. Key steps include:

1. soundio_create() to initialize the library.
2. soundio_connect() to connect to the audio backend.
3. soundio_default_output_device_index() to find the default device.
4. soundio_outstream_create() and soundio_outstream_open() to prepare the stream.
5. Setting a write_callback to provide audio data.
6. soundio_outstream_start() to begin playback.

#include <soundio/soundio.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>

static const float PI = 3.1415926535f;
static float seconds_offset = 0.0f;
static void write_callback(struct SoundIoOutStream *outstream, 
        int frame_count_min, int frame_count_max)
{
    // ... implementation of sine wave generation ...
}

int main(int argc, char **argv) {
    struct SoundIo *soundio = soundio_create();
    soundio_connect(soundio);
    soundio_flush_events(soundio);

    int default_out_device_index = soundio_default_output_device_index(soundio);
    struct SoundIoDevice *device = soundio_get_output_device(soundio, default_out_device_index);
    struct SoundIoOutStream *outstream = soundio_outstream_create(device);
    outstream->format = SoundIoFormatFloat32NE;
    outstream->write_callback = write_callback;

    soundio_outstream_open(outstream);
    soundio_outstream_start(outstream);

    for (;;) soundio_wait_events(soundio);

    soundio_outstream_destroy(outstream);
    soundio_device_unref(device);
    soundio_destroy(soundio);
    return 0;
}