private static int ResolveRequiredChunkLength(WaveformDescription waveform)
{
if (waveform == null)
{
throw new ArgumentNullException("waveform");
}
if (waveform.Waveform == Waveform.Dc)
{
return(1);
}
return((int)waveform.SamplingRate);
}
/// <devdoc>
/// If chunck length is higher than sampling rate then then only first one second epoch
/// will contain the impulse.
/// </devdoc>
private static double[] CreateImpulse(WaveformDescription waveform, int chunckLength)
{
Debug.Assert(waveform != null);
Debug.Assert(waveform.SamplingRate > 0);
double[] samples = new double[(int)waveform.SamplingRate];
int impulseIndex = (int)((waveform.Phase / (Math.PI * 2)) * waveform.SamplingRate);
for (int i = 0; i < samples.Length; ++i)
{
samples[i] = waveform.Offset + (i == impulseIndex ? waveform.Amplitude : 0);
}
return(samples);
}
private static double[] CreateDc(WaveformDescription waveform, int chunckLength)
{
Debug.Assert(waveform != null);
Debug.Assert(chunckLength > 0);
double[] samples = new double[chunckLength];
double value = waveform.Amplitude + waveform.Offset;
for (int i = 0; i < samples.Length; ++i)
{
samples[i] = value;
}
return(samples);
}
private static double[] CreateSine(WaveformDescription waveform, int chunckLength)
{
Debug.Assert(waveform != null);
Debug.Assert(waveform.SamplingRate > 0);
Debug.Assert((int)waveform.SamplingRate == chunckLength, "Generation of epochs longer than one second is not currently supported.");
if (waveform.Frequency == 0)
{
return(CreateDc(waveform, chunckLength));
}
double[] samples = new double[chunckLength];
double n = (waveform.Frequency / waveform.SamplingRate) * (Math.PI * 2);
for (int i = 0; i < samples.Length; ++i)
{
samples[i] = waveform.Offset + waveform.Amplitude * Math.Sin(waveform.Phase + i * n);
}
return(samples);
}
public static double[] Create(WaveformDescription waveform, int chunckLength)
{
Debug.Assert(waveform != null);
if (waveform.Waveform == Waveform.Dc)
{
return(CreateDc(waveform, chunckLength));
}
if (waveform.Waveform == Waveform.Sine)
{
return(CreateSine(waveform, chunckLength));
}
if (waveform.Waveform == Waveform.Impulse)
{
return(CreateImpulse(waveform, chunckLength));
}
throw new InvalidEnumArgumentException("waveform.Waveform", (int)waveform.Waveform, typeof(Waveform));
}
/// <summary>
/// Initializes a new instance of <see cref="WaveGenerator"/>.
/// </summary>
/// <param name="waveform">
/// Description of the waveform to synthesize. Note that, for <see cref="Waveform.Sine"/>, if sampling rate <see cref="WaveformDescription.SamplingRate"/>
/// is not an integer value then there may be a visible error at the end of each second in the generated waveform.
/// Also note that, because waveform is synthesized when this object is constructed, there may be an <see cref="OutOfMemoryException"/>
/// if sampling rate is extremely high (one full epoch of one second will be generated for all waveforms but <see cref="Waveform.Dc"/>)
/// or <see cref="ArgumentOutOfRangeException"/> when you set <c>WaveformDescription.SamplingRate</c> if required value is higher
/// than <see cref="WaveformDescription.MaximumSamplingRate"/>.
/// </param>
/// <exception cref="ArgumentNullException">
/// If <paramref name="waveform"/> is <see langword="null"/>.
/// </exception>
public WaveGenerator(WaveformDescription waveform)
: base(WaveformFactory.Create(waveform, ResolveRequiredChunkLength(waveform)))
{
}
