Using ofSoundStream to play arbitrary audio data

If you're looking for the ability to pipe raw audio through OpenFrameworks, and aren't interested in using the built in ofSoundPlayer objects, start here. Grimus has put up some very nice code for what is essentially a framework for loading, playing, and effecting audio in a manner that'll be familiar and easy for those looking to do DSP.


If you just want a bare-bones explanation, I'll give you a little overview here. In your application's setup() method, you need to setup the ofSoundStream with a reference to your application, and some other information like the sample rate:

void testApp::setup(){

 

...

sampleRate = 44100;

lAudio = new float[256];

rAudio = new float[256];

ofSoundStreamSetup(2, 0, this, sampleRate, 256, 4);

...

}

In the above case, we are setting up the ofSoundStream with 2 output channels, 0 input channels, a reference to our application, the sample rate of 44100 hz, a buffer length of 256 samples, and 4 somethings (I forget what the four is for). Once you've done this, your application will periodically be asked to fill a buffer full of audio for output. To ensure that the application can properly respond to this request, you need to implement the following method in your testApp implementation (testApp.cpp or whatever you've called it). Make sure you also update your header file!

void testApp::audioRequested (float * output, int bufferSize, int nChannels){

    for (int i = 0; i < bufferSize; i++){

lAudio[i] = output[i*nChannels    ] = left_channel_sample_goes_here;

rAudio[i] = output[i*nChannels + 1] = right_channel_sample_goes_here;

    }

}

At this point, you are now responsible for filling up 256 (as defined above for the buffer size) samples of audio output every time the method is called. We save the outputted audio in the lAudio and rAudio buffers in case we'd like to graph the output or do something else nifty with recent output.

That's all there is to it!