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https://github.com/thestk/stk
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71 lines
2.7 KiB
Plaintext
71 lines
2.7 KiB
Plaintext
/*! \page multichannel Multi-Channel I/O
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The ToolKit WvIn and WvOut classes (and their subclasses) support multi-channel audio data input and output. A set of interleaved audio samples representing a single time "slice" is referred to as a <I>sample frame</I>. At a sample rate of 44.1 kHz, a four-channel audio stream will have 44100 sample frames per second and a total of 176400 individual samples per second.
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Most STK classes process single-sample data streams via their <TT>tick()</TT> function. In order to distinguish single-sample and sample frame calculations, the WvIn and WvOut classes implement both <TT>tick()</TT> and <TT>tickFrame()</TT> functions. The <TT>tickFrame()</TT> functions take or return a pointer to an array of audio data representing one or more sample frames. For single-channel streams, the <TT>tick()</TT> and <TT>tickFrame()</TT> functions produce equivalent results. When <TT>tick()</TT> 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).
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Multi-channel support for realtime audio input and output is dependent on the audio device(s) available on your system.
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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.
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\code
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// foursine.cpp
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#include "WaveLoop.h"
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#include "WvOut.h"
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int main()
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{
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// Set the global sample rate before creating class instances.
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Stk::setSampleRate( 44100.0 );
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int i, j;
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WvOut *output = 0;
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WaveLoop *inputs[4];
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for ( i=0; i<4; i++ ) inputs[i] = 0;
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// Define and load the sine waves
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try {
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for ( i=0; i<4; i++ ) {
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inputs[i] = new WaveLoop( "rawwaves/sinewave.raw", TRUE );
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inputs[i]->setFrequency( 220.0 * (i+1) );
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}
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}
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catch (StkError &) {
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goto cleanup;
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}
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// Define and open a 16-bit, four-channel AIFF formatted output file
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try {
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output = new WvOut( "foursine.aif", 4, WvOut::WVOUT_AIF, Stk::STK_SINT16 );
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}
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catch (StkError &) {
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goto cleanup;
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}
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// Write two seconds of four sines to the output file
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MY_FLOAT frame[4];
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for ( j=0; j<88200; j++ ) {
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for ( i=0; i<4; i++ )
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frame[i] = inputs[i]->tick();
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output->tickFrame( frame );
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}
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// Now write the first sine to all four channels for two seconds
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for ( j=0; j<88200; j++ ) {
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output->tick( inputs[0]->tick() );
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}
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cleanup:
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for ( i=0; i<4; i++ ) delete inputs[i];
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delete output;
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return 0;
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}
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\endcode
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[<A HREF="polyvoices.html">Next tutorial</A>] [<A HREF="tutorial.html">Main tutorial page</A>]
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*/
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