Callback APIs

Vivox Core

The vx_sdk_config_t structure has six fields for registering callback function pointers related to audio buffers and the audio subsystem. Note that these callback pointers must be set at the time of the Vivox SDK initialization. This structure is passed in when calling vx_initialize3() and cannot be set or altered by other code modules afterwards. You only need to set the callbacks that you plan to use.

After the callbacks are set, they are called from the Vivox real-time audio processing thread. Any blocking operations (for example, memory allocation or writing data to storage) should be performed on another thread to prevent blocking audio processing.

The following code snippet shows an example of how to set the callback pointers.

// Called after audio is read from the capture device.
// This is as close to the capture device as possible, but can still
// have audio adjustments due to hardware echo cancellation and other
// factors.
// No blocking operations can occur on this callback.
void(*pf_on_audio_unit_after_capture_audio_read)(
 void *callback_handle,
 const char *session_group_handle,
 const char *initial_target_uri,
 short *pcm_frames,      // frame buffer
 int pcm_frame_count,    // number of frames in buffer
 int audio_frame_rate,   // sample rate, can switch mid-stream
 int channels_per_frame  // channels per frame
);

// Called when an audio processing unit is about to
// send captured audio to the network from the audio processing
// thread.
// No blocking operation can occur on this callback.
void(*pf_on_audio_unit_before_capture_audio_sent)(
 void *callback_handle,
 const char *session_group_handle,
 const char *initial_target_uri,
 short *pcm_frames,      // frame buffer
 int pcm_frame_count,    // number of frames in buffer
 int audio_frame_rate,   // sample rate, can switch mid-stream
 int channels_per_frame  // channels per frame
);

// Called before an audio processing unit mixes the per-participant
// audio data to a single stream from the audio processing thread.
// No blocking operations can occur on this callback.
void (*pf_on_audio_unit_before_recv_audio_mixed_t)(
  void *callback_handle,
  const char *session_group_handle,
  const char *initial_target_uri,
 vx_before_recv_audio_mixed_participant_data_t *participants_data,
  size_t num_participants
);

// Called when an audio processing unit is about to write received
// audio to the render device from the audio processing thread.
// No blocking operations can occur on this callback.
void(*pf_on_audio_unit_before_recv_audio_rendered)(
 void *callback_handle,
 const char *session_group_handle,
 const char *initial_target_uri,
 short *pcm_frames,      // frame buffer
 int pcm_frame_count,    // number of frames in buffer
 int audio_frame_rate,   // sample rate, can switch mid-stream
 int channels_per_frame, // channels per frame
 int is_silence          // equals 0 if there is renderable audio data
);

// Called when an audio processing unit is started
// from the audio processing thread.
// No blocking operations can occur on this callback.
void(*pf_on_audio_unit_started)(
 void *callback_handle,
 const char *session_group_handle,
 const char *initial_target_uri);

// Called when an audio processing unit is stopped
// from the audio processing thread.
// No blocking operations can occur on this callback.
void(*pf_on_audio_unit_stopped)(
 void *callback_handle,
 const char *session_group_handle,
 const char *initial_target_uri);

Callback APIs#

Vivox Core#

Callback APIs

Vivox Core