Cross-platform Audio Streaming - Android NDK Game Development - page 138

9. In the Update() method, we use the StreamBuffer() member function, which

does the job of illing the buffer with decoded or generated data from the provider:
int StreamBuffer( unsigned int BufferID, int Size )
{
int ActualSize =
FWaveDataProvider->StreamWaveData(Size);

ubyte* Data = FWaveDataProvider->GetWaveData();
int Sz = (int)FWaveDataProvider->GetWaveDataSize();

alBufferData( BufferID,
FWaveDataProvider->GetALFormat(),
Data, Sz,
FWaveDataProvider->FSamplesPerSec );

return ActualSize;
}

10. The BUFFER_SIZE constant is set to be big enough to hold the data for a couple of
seconds of streamed data:

const int BUFFER_SIZE = 352800;

The value 352800 is derived as follows:
2 channels × 44,100 samples per second × 2 bytes per sample × 2
seconds = 352,800 bytes .

How it works…

The code in this recipe does not implement the StreamWaveData() method. To hear
something from the speakers, we write the ToneGenerator class, which generates a pure
sine wave as the output data. This class is derived from StreamingWaveDataProvider :

class ToneGenerator : public StreamingWaveDataProvider
{

The parameters of the signal and an internal sample counter are declared irst:

int FSignalFreq;
float FFrequency;
float FAmplitude;
private:
int LastOffset;