public static CTCSSDecoder Create(float tone, int sampleRate)
{
if (!ValidTones.Contains(tone))
{
throw new ArgumentOutOfRangeException(nameof(tone), @"is not a valid CTCSS tone");
}
if (sampleRate <= 0)
{
throw new ArgumentOutOfRangeException(nameof(sampleRate), @"value must be greater than 0");
}
float binWidthInHz = CalculateBinWidthForTone(tone);
float numberOfSamplesForRequiredBinWidth = sampleRate / binWidthInHz;
float samplesRequiredForOnePEriod = sampleRate / tone;
int frameSize = (int)Math.Round(numberOfSamplesForRequiredBinWidth + (numberOfSamplesForRequiredBinWidth % samplesRequiredForOnePEriod));
var frequenciesOfInterest = new[] { tone - binWidthInHz, tone, tone + binWidthInHz };
var lowPass = new LowPassFilter(sampleRate, tone + 10);
var goertzel = Goertzel.Create(frameSize, sampleRate, FFTWindowBuilder.Hann(frameSize), lowPass.Process, frequenciesOfInterest);
return(new CTCSSDecoder(goertzel, frameSize, binWidthInHz));
}
private CTCSSDecoder(Goertzel goertzel, int frameSize, float binWidthInHz)
{
_binWidthInHz = binWidthInHz;
_goertzel = goertzel;
_frameSize = frameSize;
}
