/// <summary>
/// The Boobook call syllable is shaped like an inverted "U". Its total duration is close to 0.15 seconds.
/// The rising portion lasts for 0.06s, followed by a turning portion, 0.03s, followed by the decending portion of 0.06s.
/// The constants for this method were obtained from the calls in a Gympie recording obtained by Yvonne Phillips.
/// </summary>
/// <param name="ev">An event containing at least one forward track i.e. a chirp.</param>
public static void SetFrequencyProfileScore(ChirpEvent ev)
{
const double risingDuration = 0.06;
const double gapDuration = 0.03;
const double fallingDuration = 0.06;
var track = ev.Tracks.First();
var profile = track.GetTrackFrequencyProfile().ToArray();
// get the first point
var firstPoint = track.Points.First();
var frameDuration = firstPoint.Seconds.Maximum - firstPoint.Seconds.Minimum;
var risingFrameCount = (int)Math.Floor(risingDuration / frameDuration);
var gapFrameCount = (int)Math.Floor(gapDuration / frameDuration);
var fallingFrameCount = (int)Math.Floor(fallingDuration / frameDuration);
var startSum = 0.0;
if (profile.Length >= risingFrameCount)
{
for (var i = 0; i <= risingFrameCount; i++)
{
startSum += profile[i];
}
}
int startFrame = risingFrameCount + gapFrameCount;
int endFrame = startFrame + fallingFrameCount;
var endSum = 0.0;
if (profile.Length >= endFrame)
{
for (var i = startFrame; i <= endFrame; i++)
{
endSum += profile[i];
}
}
// set score to 1.0 if the profile has inverted U shape.
double score = 0.0;
if (startSum > 0.0 && endSum < 0.0)
{
score = 1.0;
}
ev.FrequencyProfileScore = score;
}
/// <summary>
/// This method returns foward (spectral peak) tracks enclosed in spectral events.
/// It averages dB log values incorrectly but it is faster than doing many log conversions.
/// </summary>
/// <param name="sonogram">The spectrogram to be searched.</param>
/// <returns>A list of acoustic events containing foward tracks.</returns>
public static (List <EventCommon> Events, double[] CombinedIntensity) GetForwardTracks(
SpectrogramStandard sonogram,
ForwardTrackParameters parameters,
TimeSpan segmentStartOffset)
{
var sonogramData = sonogram.Data;
int frameCount = sonogramData.GetLength(0);
int binCount = sonogramData.GetLength(1);
int nyquist = sonogram.NyquistFrequency;
double binWidth = nyquist / (double)binCount;
int minBin = (int)Math.Round(parameters.MinHertz.Value / binWidth);
int maxBin = (int)Math.Round(parameters.MaxHertz.Value / binWidth);
double minDuration = parameters.MinDuration.Value;
double maxDuration = parameters.MaxDuration.Value;
double decibelThreshold = parameters.DecibelThreshold.Value;
var converter = new UnitConverters(
segmentStartOffset: segmentStartOffset.TotalSeconds,
sampleRate: sonogram.SampleRate,
frameSize: sonogram.Configuration.WindowSize,
frameOverlap: sonogram.Configuration.WindowOverlap);
//Find all spectral peaks and place in peaks matrix
var peaks = new double[frameCount, binCount];
for (int row = 0; row < frameCount; row++)
{
for (int col = minBin + 1; col < maxBin - 1; col++)
{
if (sonogramData[row, col] < decibelThreshold)
{
continue;
}
// if given matrix element is greater than in freq bin either side
bool isPeak = (sonogramData[row, col] > sonogramData[row, col - 1]) && (sonogramData[row, col] > sonogramData[row, col + 1]);
if (isPeak)
{
peaks[row, col] = sonogramData[row, col];
}
}
}
var tracks = GetForwardTracks(peaks, minDuration, maxDuration, decibelThreshold, converter);
// initialise tracks as events and get the combined intensity array.
// list of accumulated acoustic events
var events = new List <SpectralEvent>();
var combinedIntensityArray = new double[frameCount];
// The following lines are used only for debug purposes.
//var options = new EventRenderingOptions(new UnitConverters(segmentStartOffset.TotalSeconds, sonogram.Duration.TotalSeconds, nyquist, frameCount, binCount));
//var spectrogram = sonogram.GetImage(doHighlightSubband: false, add1KHzLines: true, doMelScale: false);
// Initialise events with tracks.
foreach (var track in tracks)
{
//Following line used only for debug purposes. Can save as image.
//spectrogram.Mutate(x => track.Draw(x, options));
var maxScore = decibelThreshold * 5;
var scoreRange = new Interval <double>(0, maxScore);
var ae = new ChirpEvent(track, scoreRange)
{
SegmentStartSeconds = segmentStartOffset.TotalSeconds,
SegmentDurationSeconds = frameCount * converter.SecondsPerFrameStep,
Name = "noName",
};
events.Add(ae);
// fill the intensity array
var startRow = converter.FrameFromStartTime(track.StartTimeSeconds);
var amplitudeTrack = track.GetAmplitudeOverTimeFrames();
for (int i = 0; i < amplitudeTrack.Length; i++)
{
combinedIntensityArray[startRow + i] = Math.Max(combinedIntensityArray[startRow + i], amplitudeTrack[i]);
}
}
List <EventCommon> returnEvents = events.Cast <EventCommon>().ToList();
// Combine coincident events that are stacked one above other.
// This will help in some cases to combine related events.
if (parameters.CombinePossibleHarmonics)
{
returnEvents = CompositeEvent.CombinePotentialStackedTracks(events, parameters.HarmonicsStartDifference, parameters.HarmonicsHertzGap);
}
// Combine events that are temporally close and in the same frequency band.
// This will help in some cases to combine related events.
if (parameters.CombinePossibleSyllableSequence)
{
var timeDiff = TimeSpan.FromSeconds(parameters.SyllableStartDifference);
returnEvents = CompositeEvent.CombineSimilarProximalEvents(events, timeDiff, parameters.SyllableHertzGap);
}
return(returnEvents, combinedIntensityArray);
}
