// 20170803
#region Comments
// This method uses Steps 2-4 of the YIN method (Cheveigne and Kawahara, 2002).
// (Step 1 is only used (in the paper) for comparison, and Steps 5-6 only provide
// minor absolute improvements.
#endregion
/* public double GetPitchPeriod(WAVSound sound, double time, double maximumPitchPeriod, double threshold)
* {
* int sampleIndex = sound.GetSampleIndexAtTime(time);
* int maximumIndexDuration = (int)Math.Round(maximumPitchPeriod * sound.SampleRate);
* double minimum = double.MaxValue;
* double pitchPeriod = 0;
* List<double> periodList = new List<double>();
* List<double> shiftedSquareDifferenceList = new List<double>();
* List<double> normalizedShiftedSquaredDifferenceList = new List<double>();
* periodList.Add(0);
* shiftedSquareDifferenceList.Add(0);
* normalizedShiftedSquaredDifferenceList.Add(1);
*
* for (int ii = 1; ii <= maximumIndexDuration; ii++)
* {
* int indexDuration = ii;
* double shiftedSquareDifference = sound.GetShiftedSquareDifference(sampleIndex, ii, maximumIndexDuration);
* shiftedSquareDifferenceList.Add(shiftedSquareDifference);
* double period = indexDuration / (double)sound.SampleRate;
* periodList.Add(period);
* double average = shiftedSquareDifferenceList.Average();
* double normalizedShiftedSquareDifference = shiftedSquareDifference / average;
* if (normalizedShiftedSquareDifference < minimum)
* {
* minimum = normalizedShiftedSquareDifference;
* pitchPeriod = period;
* }
* normalizedShiftedSquaredDifferenceList.Add(normalizedShiftedSquareDifference);
* }
* int minimumIndex = FindFirstMinimum(normalizedShiftedSquaredDifferenceList, threshold);
* if (minimumIndex > 0) // Otherwise use the global minimum, computed above.
* {
* pitchPeriod = minimumIndex / (double)sound.SampleRate;
* }
* return pitchPeriod;
* } */
public double ComputeFramePitchPeriod(WAVSound sound, double time)
// , double minimumPitchPeriod, double maximumPitchPeriod)
{
int sampleIndex = sound.GetSampleIndexAtTime(time);
int minimumIndexDuration = (int)Math.Round(minimumPitchPeriod * sound.SampleRate);
int maximumIndexDuration = (int)Math.Round(maximumPitchPeriod * sound.SampleRate);
double minimumAverageMagnitudeDifference = double.MaxValue;
int indexDurationAtMinimum = 0;
for (int ii = minimumIndexDuration; ii <= maximumIndexDuration; ii++)
{
double averageMagnitudeDifference = sound.GetAbsoluteMagnitudeDifference(sampleIndex, ii, maximumIndexDuration);
if (averageMagnitudeDifference < minimumAverageMagnitudeDifference)
{
minimumAverageMagnitudeDifference = averageMagnitudeDifference;
indexDurationAtMinimum = ii;
}
}
double pitchPeriod = indexDurationAtMinimum / (double)sound.SampleRate;
return(pitchPeriod);
}