cubeb

Introduction

This is the documentation for the libcubeb C API. libcubeb is a callback-based audio API library allowing the authoring of portable multiplatform audio playback and recording.

Example code

This example shows how to create a duplex stream that pipes the microphone to the speakers, with minimal latency and the proper sample-rate for the platform.

cubeb * app_ctx;
cubeb_init(&app_ctx, "Example Application", NULL);
int rv;
uint32_t rate;
uint32_t latency_frames;
uint64_t ts;
 
rv = cubeb_get_preferred_sample_rate(app_ctx, &rate);
if (rv != CUBEB_OK) {
  fprintf(stderr, "Could not get preferred sample-rate");
  return rv;
}
 
cubeb_stream_params output_params;
output_params.format = CUBEB_SAMPLE_FLOAT32NE;
output_params.rate = rate;
output_params.channels = 2;
output_params.layout = CUBEB_LAYOUT_UNDEFINED;
output_params.prefs = CUBEB_STREAM_PREF_NONE;
 
rv = cubeb_get_min_latency(app_ctx, &output_params, &latency_frames);
if (rv != CUBEB_OK) {
  fprintf(stderr, "Could not get minimum latency");
  return rv;
}
 
cubeb_stream_params input_params;
input_params.format = CUBEB_SAMPLE_FLOAT32NE;
input_params.rate = rate;
input_params.channels = 1;
input_params.layout = CUBEB_LAYOUT_UNDEFINED;
input_params.prefs = CUBEB_STREAM_PREF_NONE;
 
cubeb_stream * stm;
rv = cubeb_stream_init(app_ctx, &stm, "Example Stream 1",
                       NULL, &input_params,
                       NULL, &output_params,
                       latency_frames,
                       data_cb, state_cb,
                       NULL);
if (rv != CUBEB_OK) {
  fprintf(stderr, "Could not open the stream");
  return rv;
}
 
rv = cubeb_stream_start(stm);
if (rv != CUBEB_OK) {
  fprintf(stderr, "Could not start the stream");
  return rv;
}
for (;;) {
  cubeb_stream_get_position(stm, &ts);
  printf("time=%llu\n", ts);
  sleep(1);
}
rv = cubeb_stream_stop(stm);
if (rv != CUBEB_OK) {
  fprintf(stderr, "Could not stop the stream");
  return rv;
}
 
cubeb_stream_destroy(stm);
cubeb_destroy(app_ctx);

long data_cb(cubeb_stream * stm, void * user,
             const void * input_buffer, void * output_buffer, long nframes)
{
  const float * in  = input_buffer;
  float * out = output_buffer;
 
  for (int i = 0; i < nframes; ++i) {
    for (int c = 0; c < 2; ++c) {
      out[2 * i + c] = in[i];
    }
  }
  return nframes;
}

void state_cb(cubeb_stream * stm, void * user, cubeb_state state)
{
  printf("state=%d\n", state);
}