Analyse only active window width

The analyser is now limited to the currently displayed window width so
zoom is not considered in the samples. Note that the fat maxes out at
zoom level 40% so any lower has no effect. Its a bit of a balance
between speed and sample size;

Author: Gary Keeble

js/graph_spectrum.js

@@ -13,7 +13,7 @@ var // inefficient; copied from grapher.js
         };
 
 
-var frameCount = 2048;
+var frameCount = 4096;
 
 var AudioContext = window.AudioContext || window.webkitAudioContext;
 var audioCtx = new AudioContext();
@@ -30,7 +30,7 @@ var spectrumAnalyser = audioCtx.createAnalyser();
 	spectrumAnalyser.minDecibels = -120;
 	spectrumAnalyser.maxDecibels = -20;    
 
-var bufferChunks, bufferStartFrameIndex, bufferFieldIndex, bufferCurve;
+var bufferChunks, bufferStartFrameIndex, bufferFieldIndex, bufferCurve, bufferWindowEndTime;
 var initialised = false;
 var analyserFieldName; // Name of the field being analysed
 
@@ -39,7 +39,7 @@ source.connect(spectrumAnalyser);
 
 var audioIterations = 0; // variable to monitor spectrum processing
 
-function dataLoad(chunks, startFrameIndex, fieldIndex, curve, buffer) {
+function dataLoad(chunks, startFrameIndex, fieldIndex, curve, buffer, windowEndTime) {
 
         var chunkIndex, frameIndex;
 		var i = 0;            
@@ -54,10 +54,13 @@ function dataLoad(chunks, startFrameIndex, fieldIndex, curve, buffer) {
             var chunk = chunks[chunkIndex];
             for (; frameIndex < chunk.frames.length; frameIndex++) {
             	var fieldValue = chunk.frames[frameIndex][fieldIndex];
+            	var frameTime  = chunk.frames[frameIndex][FlightLogParser.prototype.FLIGHT_LOG_FIELD_INDEX_TIME]
                 bufferData[i++] = (curve.lookupRaw(fieldValue));
-
-                if (i >= buffer.length)
+                    
+                if (i >= buffer.length || frameTime >= windowEndTime) {
+					// console.log("Samples : " + i);
                     break dataCollectionLoop;
+                    }
             }
             frameIndex = 0;
         }
@@ -147,16 +150,18 @@ function drawAxisLabel(axisLabel, X, Y, align) {
    It is only used to record the current curve positions, collect the data and draw the 
    analyser on screen*/
 
-this.plotSpectrum =	function (chunks, startFrameIndex, fieldIndex, curve, fieldName) {
+this.plotSpectrum =	function (chunks, startFrameIndex, fieldIndex, curve, fieldName, windowEndTime) {
 		// Store the data pointers
 		bufferChunks = chunks;
 		bufferStartFrameIndex = startFrameIndex;
 		bufferFieldIndex = fieldIndex;
 		bufferCurve = curve;
+		bufferWindowEndTime = windowEndTime;
+
 	    analyserFieldName = fieldName;
 
 		if (audioBuffer) {
-			dataLoad(bufferChunks, bufferStartFrameIndex, bufferFieldIndex, bufferCurve, audioBuffer);
+			dataLoad(bufferChunks, bufferStartFrameIndex, bufferFieldIndex, bufferCurve, audioBuffer, bufferWindowEndTime);
 		}
 		draw(); // draw the analyser on the canvas....
 	}

js/grapher.js

@@ -820,7 +820,7 @@ function FlightLogGrapher(flightLog, graphConfig, canvas, craftCanvas, options)
                 try{ // If we do not select a graph/field, then the analyser is hidden
                 var graph = graphs[graphConfig.selectedGraphIndex]; 		
 				var field = graph.fields[graphConfig.selectedFieldIndex];   	            
-                analyser.plotSpectrum(chunks, startFrameIndex, field.index, field.curve, graphConfig.selectedFieldName);
+                analyser.plotSpectrum(chunks, startFrameIndex, field.index, field.curve, graphConfig.selectedFieldName, windowEndTime);
                 } catch(err) {console.log('Cannot plot analyser');}            
             }
         }