layout: doc title: “Starboard Module Reference: audio_sink.h”

Provides an interface to output raw audio data.



Well-defined value for an invalid audio sink.



An opaque handle to an implementation-private structure representing an audio sink.


typedef struct SbAudioSinkPrivate* SbAudioSink


Callback used to report frames consumed. The consumed frames will be removed from the source frame buffer to free space for new audio frames.


typedef void(* SbAudioSinkConsumeFramesFunc) (int frames_consumed, void *context)


An array of frame buffers. For interleaved audio streams, there will be only one element in the array. For planar audio streams, the number of elements in the array equal to the number of channels.


typedef void** SbAudioSinkFrameBuffers


Callback being called periodically to retrieve the status of the audio source. The first two output parameters indicating the filling level of the audio frame buffer passed to SbAudioSinkCreate as frame_buffers. As frame_buffers is a circular buffer, offset_in_frames can be used to calculate the number of continuous frames towards the end of the buffer. The audio sink can play the frames only when is_playing is true. It should pause the playback when is_playing is false. The audio sink may cache certain amount of audio frames before start playback. It will start playback immediately when is_eos_reached is true even if the amount of cached audio frames are not enough as no more frames will be appended into the buffer when is_eos_reached is true. It is possible for a host to set is_eos_reached to false after setting it to true, usually this is caused by a seek. All parameters except context cannot be NULL. Note that this function only reports the status of the source, it doesn't remove audio data from the source frame buffer.


typedef void(* SbAudioSinkUpdateSourceStatusFunc) (int *frames_in_buffer, int *offset_in_frames, bool *is_playing, bool *is_eos_reached, void *context)



Destroys audio_sink, freeing all associated resources. Before returning, the function waits until all callbacks that are in progress have finished. After the function returns, no further calls are made callbacks passed into SbAudioSinkCreate. In addition, you can not pass audio_sink to any other SbAudioSink functions after SbAudioSinkDestroy has been called on it.

This function can be called on any thread. However, it cannot be called within any of the callbacks passed into SbAudioSinkCreate.

audio_sink: The audio sink to destroy.


void SbAudioSinkDestroy(SbAudioSink audio_sink)


Returns the maximum number of channels supported on the platform. For example, the number would be 2 if the platform only supports stereo.


int SbAudioSinkGetMaxChannels()


Returns the minimum frames required by audio sink to play without underflows. Returns -1, if channels, sample_type or sampling_frequency_hz is not supported. It‘s user’s responsibility to ensure that there're enough frames written into audio sink during playing, or it may have underflows.

channels: The number of audio channels, such as left and right channels in stereo audio. audio_sample_type: The type of each sample of the audio data – int16, float32, etc. sampling_frequency_hz: The sample frequency of the audio data being streamed. For example, 22,000 Hz means 22,000 sample elements represents one second of audio data.


int SbAudioSinkGetMinBufferSizeInFrames(int channels, SbMediaAudioSampleType sample_type, int sampling_frequency_hz)


Returns the supported sample rate closest to sampling_frequency_hz. On platforms that don‘t support all sample rates, it is the caller’s responsibility to resample the audio frames into the supported sample rate returned by this function.


int SbAudioSinkGetNearestSupportedSampleFrequency(int sampling_frequency_hz)


Indicates whether audio_frame_storage_type is supported on this platform.


bool SbAudioSinkIsAudioFrameStorageTypeSupported(SbMediaAudioFrameStorageType audio_frame_storage_type)


Indicates whether audio_sample_type is supported on this platform.


bool SbAudioSinkIsAudioSampleTypeSupported(SbMediaAudioSampleType audio_sample_type)


Indicates whether the given audio sink handle is valid.

audio_sink: The audio sink handle to check.


bool SbAudioSinkIsValid(SbAudioSink audio_sink)