/// <summary>
/// A click is a sharp onset broadband sound of brief duration. Geometrically it is similar to a vertical whistle.
/// THis method averages dB log values incorrectly but it is faster than doing many log conversions.
/// This method is used to find acoustic events and is accurate enough for the purpose.
/// </summary>
public static (List <AcousticEvent> Events, double[] Intensity) GetClicks(
SpectrogramStandard sonogram,
int minHz,
int maxHz,
int nyquist,
double decibelThreshold,
int minBandwidthHertz,
int maxBandwidthHertz,
bool combineProximalSimilarEvents,
TimeSpan segmentStartOffset)
{
var sonogramData = sonogram.Data;
int frameCount = sonogramData.GetLength(0);
int binCount = sonogramData.GetLength(1);
double binWidth = nyquist / (double)binCount;
int minBin = (int)Math.Round(minHz / binWidth);
int maxBin = (int)Math.Round(maxHz / binWidth);
int bandwidthBinCount = maxBin - minBin + 1;
// list of accumulated acoustic events
var events = new List <AcousticEvent>();
var temporalIntensityArray = new double[frameCount];
// for all time frames except 1st and last allowing for edge effects.
for (int t = 1; t < frameCount - 1; t++)
{
// set up an intensity array for all frequency bins in this frame.
double[] clickIntensity = new double[bandwidthBinCount];
// buffer zone around click is one frame wide.
// for all frequency bins except top and bottom in this time frame
for (int bin = minBin; bin < maxBin; bin++)
{
// THis is where the profile of a click is defined
// A click requires sudden onset, with maximum amplitude followed by decay.
if (sonogramData[t - 1, bin] > decibelThreshold || sonogramData[t, bin] < sonogramData[t + 1, bin])
{
continue;
}
// THis is where the profile of a vertical ridge is defined
//if (sonogramData[t, bin] < sonogramData[t - 1, bin] || sonogramData[t, bin] < sonogramData[t + 1, bin])
//{
// continue;
//}
clickIntensity[bin - minBin] = sonogramData[t, bin];
//clickIntensity[bin - minBin] = sonogramData[t, bin] - sonogramData[t - 1, bin];
clickIntensity[bin - minBin] = Math.Max(0.0, clickIntensity[bin - minBin]);
}
if (clickIntensity.Max() < decibelThreshold)
{
continue;
}
// Extract the events based on bandwidth and threshhold.
var acousticEvents = ConvertSpectralArrayToClickEvents(
clickIntensity,
minHz,
sonogram.FramesPerSecond,
sonogram.FBinWidth,
decibelThreshold,
minBandwidthHertz,
maxBandwidthHertz,
t,
segmentStartOffset);
// add each event score to combined temporal intensity array
foreach (var ae in acousticEvents)
{
var avClickIntensity = ae.Score;
temporalIntensityArray[t] += avClickIntensity;
}
// add new events to list of events
events.AddRange(acousticEvents);
}
// combine proximal events that occupy similar frequency band
var startDifference = TimeSpan.FromSeconds(1.0);
var hertzDifference = 100;
if (combineProximalSimilarEvents)
{
events = AcousticEvent.CombineSimilarProximalEvents(events, startDifference, hertzDifference);
}
return(events, temporalIntensityArray);
}
/// <summary>
/// EXPANATION: A vertical track is a near click or rapidly frequency-modulated tone. A good example is the whip component of the whip-bird call.
/// They would typically be only a few time-frames duration.
/// THis method averages dB log values incorrectly but it is faster than doing many log conversions and is accurate enough for the purpose.
/// </summary>
public static (List <AcousticEvent> Events, double[] CombinedIntensity) GetVerticalTracks(
SpectrogramStandard sonogram,
int minHz,
int maxHz,
int nyquist,
double decibelThreshold,
int minBandwidthHertz,
int maxBandwidthHertz,
bool combineProximalSimilarEvents,
TimeSpan segmentStartOffset)
{
var sonogramData = sonogram.Data;
int frameCount = sonogramData.GetLength(0);
int binCount = sonogramData.GetLength(1);
var frameDuration = sonogram.FrameDuration;
var frameStep = sonogram.FrameStep;
var frameOverStep = frameDuration - frameStep;
double binWidth = nyquist / (double)binCount;
int minBin = (int)Math.Round(minHz / binWidth);
int maxBin = (int)Math.Round(maxHz / binWidth);
// list of accumulated acoustic events
var events = new List <AcousticEvent>();
var temporalIntensityArray = new double[frameCount];
//Find all frame peaks and place in peaks matrix
var peaks = new double[frameCount, binCount];
for (int row = 1; row < frameCount - 1; row++)
{
for (int col = minBin; col < maxBin; col++)
{
if (sonogramData[row, col] < decibelThreshold)
{
continue;
}
// if given matrix element is greater than in frame either side
bool isPeak = (sonogramData[row, col] > sonogramData[row - 1, col]) && (sonogramData[row, col] > sonogramData[row + 1, col]);
if (isPeak)
{
peaks[row, col] = sonogramData[row, col];
}
}
}
// Look for track starts and initialise them as events.
// Cannot include edge rows & columns because of edge effects.
// Each row is a time frame which is a spectrum. Each column is a frequency bin
var combinedIntensityArray = new double[frameCount];
for (int col = minBin; col < maxBin; col++)
{
for (int row = 2; row < frameCount - 2; row++)
{
// Visit each frame peak in order. Each may be start of possible track
if (peaks[row, col] < decibelThreshold)
{
continue;
}
//have the beginning of a potential track
var track = GetVerticalTrack(peaks, row, col, maxBin, decibelThreshold);
// calculate first and last of the frame IDs in the original spectrogram
int trackStartFrame = track.GetStartFrame();
int trackEndFrame = track.GetEndFrame();
// next two for debug purposes
//int trackMinBin = track.GetBottomFreqBin();
//int trackTopBin = track.GetTopFreqBin();
//If track has lies within the correct bandWidth range, then create an event
int trackBandWidth = track.GetTrackBandWidthHertz(binWidth);
if (trackBandWidth >= minBandwidthHertz && trackBandWidth <= maxBandwidthHertz)
{
// get the oblong and init an event
double trackDuration = ((trackEndFrame - trackStartFrame) * frameStep) + frameOverStep;
var oblong = new Oblong(trackStartFrame, col, trackEndFrame, track.GetTopFreqBin());
var ae = new AcousticEvent(segmentStartOffset, oblong, nyquist, binCount, frameDuration, frameStep, frameCount)
{
// get the track as matrix
TheTrack = track,
};
events.Add(ae);
// fill the intensity array
var amplitudeArray = track.GetAmplitudeOverTimeFrames();
for (int i = 0; i < amplitudeArray.Length; i++)
{
combinedIntensityArray[row + i] += amplitudeArray[i];
}
}
} // rows/frames
} // end cols/bins
// combine proximal events that occupy similar frequency band
if (combineProximalSimilarEvents)
{
TimeSpan startDifference = TimeSpan.FromSeconds(0.5);
int hertzDifference = 500;
events = AcousticEvent.CombineSimilarProximalEvents(events, startDifference, hertzDifference);
}
return(events, temporalIntensityArray);
}