/*
* ================ Miscellaneous ================
*/
public void filterSelectedFrequencies(DSP_FILTER method = DSP_FILTER.convolution)
{
if (fSelStart == fSelEnd)
{
return;
}
double[] filter = new double[fourierN];
for (int fbin = 0; fbin < filter.Length; fbin++)
{
if ((fbin >= fSelStart && fbin <= fSelEnd) || (fbin >= fourierN - fSelEnd && fbin <= fourierN - fSelStart))
{
filter[fbin] = 0;
}
else
{
filter[fbin] = 1;
}
}
double criticalPoint = 0;
if (method == DSP_FILTER.IIRLowpass)
{
criticalPoint = fSelStart * SampleRate / fourierN;
}
else
{
criticalPoint = fSelEnd * SampleRate / fourierN;
}
for (int channel = 0; channel < wave.channels; channel++)
{
switch (method)
{
case DSP_FILTER.convolution:
wave.samples[channel] = DSP.convolveFilter(ref wave.samples[channel], filter);
break;
case DSP_FILTER.DFT:
wave.samples[channel] = DSP.dftFilter(wave.samples[channel], filter);
break;
case DSP_FILTER.IIRLowpass: //low pass
// LowPass IIRFilter ( samples, 1x freq, 0x freq, 0, SampleRate );
wave.samples[channel] = DSP.IIRFilter(wave.samples[channel], Math.Min(criticalPoint + 5000, SampleRate / 2), Math.Max(0, criticalPoint - 5000), 0, SampleRate);
break;
case DSP_FILTER.IIRHighpass: //high pass
// HighPass IIRFilter ( samples, 0x freq, 1x freq, 1, SampleRate );
wave.samples[channel] = DSP.IIRFilter(wave.samples[channel], Math.Max(0, criticalPoint - 7000), Math.Min(criticalPoint + 3000, SampleRate / 2), 1, SampleRate);
break;
default:
MessageBox.Show("something went wrong.");
break;
}
}
panelWave.setSamples(wave.samples);
panelWave.Invalidate();
calculateDFT();
invalidPlayer = true;
}
/// <summary>
/// Resample audio from one sample rate to another.
/// Works by inserting 0s between existing samples at a particular ratio,
/// running a lowpass filter,
/// and selecting samples at a different ratio.
/// </summary>
/// <param name="samples"></param>
/// <param name="oldRate"></param>
/// <param name="newRate"></param>
/// <returns></returns>
public static double[] resample(ref double[] samples, int oldRate, int newRate)
{
double[] extendedSamples, result;
int L, M;
if (newRate == oldRate)
{
return(samples);
}
else if (newRate == 2 * oldRate)
{
L = 2; M = 1;
}
else if (newRate == 4 * oldRate)
{
L = 4; M = 1;
}
else if (newRate == 8 * oldRate)
{
L = 8; M = 1;
}
else if (newRate * 2 == oldRate)
{
L = 1; M = 2;
}
else if (newRate * 4 == oldRate)
{
L = 1; M = 4;
}
else if (newRate * 8 == oldRate)
{
L = 1; M = 8;
}
else
{
return(null);
}
//insert L-1 0s between each sample
extendedSamples = new double[samples.Length * L];
int i = 0;
for (int s = 0; s < samples.Length; s++)
{
extendedSamples[i] = samples[s];
i++;
for (int extra = 0; extra < L - 1; extra++)
{
extendedSamples[i] = 0;
i++;
}
}
//lowpass filter
int S = Math.Min(oldRate, newRate);
extendedSamples = DSP.IIRFilter(extendedSamples, S / 2 + 5000, S / 2 - 5000, 0, S * 2);
//select every Mth sample.
result = new double[extendedSamples.Length / M];
i = 0;
for (int s = 0; s < extendedSamples.Length; s += M)
{
result[i++] = extendedSamples[s];
}
return(result);
}