Resolved issue computing PSD for full file length segment size

Author: demvlad

src/graph_spectrum.js

@@ -348,13 +348,6 @@ export function FlightLogAnalyser(flightLog, canvas, analyserCanvas) {
       })
       .val(DEFAULT_PSD_SEGMENT_LENGTH_POWER);
 
-    analyserSegmentLengthPowerAt2
-      .on(
-        "keydown",
-        function (e) {
-          e.preventDefault();
-        },
-      );
     // Spectrum type to show
     userSettings.spectrumType =
       userSettings.spectrumType || SPECTRUM_TYPE.FREQUENCY;

src/graph_spectrum_calc.js

@@ -35,7 +35,7 @@ export const GraphSpectrumCalc = {
   _flightLog : null,
   _sysConfig : null,
   _motorPoles : null,
-  _pointsPerSegmentPSD : 0,
+  _pointsPerSegmentPSD : 64,
 };
 
 GraphSpectrumCalc.initialize = function(flightLog, sysConfig) {
@@ -119,16 +119,15 @@ GraphSpectrumCalc.setPointsPerSegmentPSD = function(pointsCount) {
 
 GraphSpectrumCalc.dataLoadPSD = function(analyserZoomY) {
   const flightSamples = this._getFlightSamplesFreq(false);
-  let pointsPerSegment, overlapCount;
-  if (this._pointsPerSegmentPSD > flightSamples.samples.length) {
-    pointsPerSegment = flightSamples.samples.length; // Use actual sample length. It will transform to power at 2 value inside the _psd() - fft_segmented
-    overlapCount = 0;
-  } else {
-    pointsPerSegment = this._pointsPerSegmentPSD;
-    overlapCount = pointsPerSegment * 3 / 4;
-  }
-
-  const psd =  this._psd(flightSamples.samples, pointsPerSegment, overlapCount);
+  const totalCount = flightSamples.count; // actual samples, not padded length
+  let pointsPerSegment = Math.min(this._pointsPerSegmentPSD, totalCount);
+  // Non-overlapping when single full-segment; otherwise 75% overlap
+  const overlapCount = (pointsPerSegment === totalCount) ? 0 : Math.floor(pointsPerSegment * 3 / 4);
+  // Avoid bias from zero-padded tail
+  const samplesForPsd = (flightSamples.samples.length === totalCount)
+    ? flightSamples.samples
+    : flightSamples.samples.slice(0, totalCount);
+  const psd = this._psd(samplesForPsd, pointsPerSegment, overlapCount);
 
   const psdData = {
     fieldIndex   : this._dataBuffer.fieldIndex,
@@ -139,7 +138,7 @@ GraphSpectrumCalc.dataLoadPSD = function(analyserZoomY) {
     minimum: psd.min,
     maximum: psd.max,
     maxNoiseFrequency: psd.maxNoiseFrequency,
-    maximalSegmentsLength: this.getNearPower2Value(flightSamples.samples.length),
+    maximalSegmentsLength: this.getNearPower2Value(totalCount),
   };
   return psdData;
 };