Can OpenSL record itself?

Question

I'd like to capture the outgoing audio from a game and record it into an audio file as it's played. Is this possible within the framework in OpenSL? Like by connecting the OutputMix to an AudioRecorder, or something?

Answer 1

You could register a callback to the queue and obtain the output buffer before / after it is enqueued into the buffer queue for output. You could have a wavBuffer (a short array the length of the buffer size) that is written into on each enqueueing of a new buffer. The contents of this buffer are then written to a file.

outBuffer = p->outputBuffer[p->currentOutputBuffer];  // obtain float buffer

for ( int i = 0; i < bufferSize; ++i )
    wavBuffer = ( short ) outBuffer[ i ] * 32768; // convert float to short

// now append contents of wavBuffer into a file

The basic OpenSL setup for the queue callback is explained in some detail on this page

And a very basic means of creating a WAV file in C++ can be found here note that you must have a pretty definitive idea of the actual size of the total WAV file as it's part of its header.