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Hello Sine!

We'll continue our introduction to the Synthesis ToolKit with a simple sine-wave oscillator program. STK does not provide a specific oscillator for sine waves. Instead, it provides a generic waveform oscillator class, WaveLoop, which can load a variety of common file types. In this example, we load a sine "table" from an STK RAW file (defined as monophonic, 16-bit, big-endian data). We use the class WvOut to write the result to a 16-bit, WAV formatted audio file.

// sineosc.cpp

#include "WaveLoop.h"
#include "WvOut.h"

int main()
{
  // Set the global sample rate before creating class instances.
  Stk::setSampleRate( 44100.0 );

  // Define and load the sine wave file
  WaveLoop* input = new WaveLoop( "rawwaves/sinewave.raw", true );
  input->setFrequency( 440.0 );

  // Define and open a 16-bit, one-channel WAV formatted output file
  WvOut* output = new WvOut( "hellosine.wav", 1, WvOut::WVOUT_WAV, Stk::STK_SINT16 );

  // Run the oscillator for 40000 samples, writing to the output file
  int i;
  for ( i=0; i<40000; i++ ) {
    output->tick( input->tick() );
  }

  // Clean up
  delete input;
  delete output;

  return 0;
}

WaveLoop is a subclass of WvIn, which supports WAV, SND (AU), AIFF, MAT-file (Matlab), and RAW file formats with 8-, 16-, and 32-bit integer and 32- and 64-bit floating-point data types. WvIn provides interpolating, read once ("oneshot") functionality, as well as methods for setting the read rate and read position.

The WvIn and WvOut classes are complementary, both supporting WAV, SND (AU), AIFF, MAT-file (Matlab), and RAW file formats with 8-, 16-, and 32-bit integer and 32- and 64-bit floating-point data types. However, WvOut does not perform data interpolation.

The WvIn and WvOut classes support multi-channel sample frames. To distinguish single-sample frame operations from multi-channel frame operations, these classes also implement tickFrame() functions. When a tick() method is called for multi-channel data, frame averages are returned or the input sample is distributed across all channels of a sample frame.

Nearly all STK classes inherit from the Stk base class. Stk provides a static sample rate which is queried by subclasses as needed. Because many classes use the current sample rate value during instantiation, it is important that the desired value be set at the beginning of a program. The default STK sample rate is 44100 Hz.

Error Handling

The ToolKit has some basic C++ error handling functionality built in. Classes which access files and/or hardware are most prone to runtime errors. To properly "catch" such errors, the above example should be rewritten as shown below.

// sineosc.cpp STK tutorial program

#include "WaveLoop.h"
#include "WvOut.h"

int main()
{
  // Set the global sample rate before creating class instances.
  Stk::setSampleRate( 44100.0 );

  WaveLoop *input = 0;
  WvOut *output = 0;

  try {
    // Define and load the sine wave file
    input = new WaveLoop( "rawwaves/sinewave.raw", true );

    // Define and open a 16-bit, one-channel WAV formatted output file
    output = new WvOut( "hellosine.wav", 1, WvOut::WVOUT_WAV, Stk::STK_SINT16 );
  }
  catch ( StkError & ) {
    goto cleanup;
  }

  input->setFrequency( 440.0 );

  // Run the oscillator for 40000 samples, writing to the output file
  int i;
  for ( i=0; i<40000; i++ ) {

    try {
      output->tick( input->tick() );
    }
    catch ( StkError & ) {
      goto cleanup;
    }

  }

 cleanup:
  delete input;
  delete output;

  return 0;
}

In this particular case, we simply exit the program if an error occurs (an error message is automatically printed to stderr). A more refined program might attempt to recover from or fix a particular problem and, if successful, continue processing. See the Class Documentation to determine which constructors and functions can throw an error.

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©1995-2004 Perry R. Cook and Gary P. Scavone. All Rights Reserved.