oboe::AudioStreamPartialDataCallback Class Reference

#include <AudioStreamCallback.h>

Public Member Functions
virtual int32_t	onPartialAudioReady (AudioStream *audioStream, void *audioData, int32_t numFrames)=0

Detailed Description

AudioStreamPartialDataCallback defines a callback interface for moving data to/from an audio stream using onAudioReady

It is used with AudioStreamBuilder::setPartialDataCallback(). The only difference between AudioStreamPartialDataCallback and AudioStreamDataCallback is that the AudioStreamPartialDataCallback allows apps to only process part of the requested data.

Note that Android only support partial data callback from aaudio API at API level 37. In that case, when partial data callback is set on the Android device that is not supporting partial data callback API, apps must process all the requested data to avoid data lost.

Call OboeExtensions::isPartialDataCallbackSupported() to check if partial data callback is supported by the device or not.

Member Function Documentation

onPartialAudioReady()

virtual int32_t oboe::AudioStreamPartialDataCallback::onPartialAudioReady ( AudioStream * audioStream, void * audioData, int32_t numFrames )

pure virtual

A buffer is ready for processing. If the client cannot process all the provided/requested data, returns a number to indicate the actual processed frames.

For an output stream, this function should render and write at most numFrames of data in the stream's current data format to the audioData buffer.

For an input stream, this function should read and process at most numFrames of data from the audioData buffer.

The audio data is passed through the buffer. So do NOT call read() or write() on the stream that is making the callback.

Note that numFrames can vary unless AudioStreamBuilder::setFramesPerCallback() is called. If AudioStreamBuilder::setFramesPerCallback() is NOT called then numFrames should always be <= AudioStream::getFramesPerBurst().

Also note that this callback function should be considered a "real-time" function. It must not do anything that could cause an unbounded delay because that can cause the audio to glitch or pop.

These are things the function should NOT do:

• allocate memory using, for example, malloc() or new
• any file operations such as opening, closing, reading or writing
• any network operations such as streaming
• use any mutexes or other synchronization primitives
• sleep
• oboeStream->stop(), pause(), flush() or close()
• oboeStream->read()
• oboeStream->write()

The following are OK to call from the data callback:

• oboeStream->get*()
• oboe::convertToText()
• oboeStream->setBufferSizeInFrames()

If you need to move data, eg. MIDI commands, in or out of the callback function then we recommend the use of non-blocking techniques such as an atomic FIFO.

Parameters

audioStream	pointer to the associated stream
audioData	buffer containing input data or a place to put output data
numFrames	number of frames to be processed

Returns

the actual processed data frames, must be within range of [0, numFrames]. Returning a negative number will stop the stream.

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The documentation for this class was generated from the following file:

• include/oboe/AudioStreamCallback.h