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Most STK classes process single-sample data streams via their tick()
function. In order to distinguish single-sample and sample frame calculations, the WvIn and WvOut classes implement both tick()
and tickFrame()
functions. The tickFrame()
functions take or return a pointer to an array of audio data representing one or more sample frames. For single-channel streams, the tick()
and tickFrame()
functions produce equivalent results. When tick()
is called for a multi-channel stream, however, the function either returns a sample frame average (WvIn) or writes a single sample argument to all channels (WvOut).
Multi-channel support for realtime audio input and output is dependent on the audio device(s) available on your system.
The following example demonstrates the use of the WvOut class for creating a four channel, 16-bit AIFF formatted audio file. We will use four sinewaves of different frequencies for the first two seconds and then a single sinewave for the last two seconds.
// foursine.cpp #include "WaveLoop.h" #include "WvOut.h" int main() { // Set the global sample rate before creating class instances. Stk::setSampleRate( 44100.0 ); int i, j; WvOut *output = 0; WaveLoop *inputs[4]; for ( i=0; i<4; i++ ) inputs[i] = 0; // Define and load the sine waves try { for ( i=0; i<4; i++ ) { inputs[i] = new WaveLoop( "rawwaves/sinewave.raw", TRUE ); inputs[i]->setFrequency( 220.0 * (i+1) ); } } catch (StkError &) { goto cleanup; } // Define and open a 16-bit, four-channel AIFF formatted output file try { output = new WvOut( "foursine.aif", 4, WvOut::WVOUT_AIF, Stk::STK_SINT16 ); } catch (StkError &) { goto cleanup; } // Write two seconds of four sines to the output file MY_FLOAT frame[4]; for ( j=0; j<88200; j++ ) { for ( i=0; i<4; i++ ) frame[i] = inputs[i]->tick(); output->tickFrame( frame ); } // Now write the first sine to all four channels for two seconds for ( j=0; j<88200; j++ ) { output->tick( inputs[0]->tick() ); } cleanup: for ( i=0; i<4; i++ ) delete inputs[i]; delete output; return 0; }
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©1995-2004 Perry R. Cook and Gary P. Scavone. All Rights Reserved. |