The Tor Browser: content/media/webaudio/test/blink/convolution-testing.js@6474c204b198 (annotated)

content/media/webaudio/test/blink/convolution-testing.js@6474c204b198 (annotated)

content/media/webaudio/test/blink/convolution-testing.js

Wed, 31 Dec 2014 06:09:35 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Wed, 31 Dec 2014 06:09:35 +0100
changeset 0: 6474c204b198
permissions: -rw-r--r--

Cloned upstream origin tor-browser at tor-browser-31.3.0esr-4.5-1-build1
revision ID fc1c9ff7c1b2defdbc039f12214767608f46423f for hacking purpose.

 var sampleRate = 44100.0;
 var renderLengthSeconds = 8;
 var pulseLengthSeconds = 1;
 var pulseLengthFrames = pulseLengthSeconds * sampleRate;
 function createSquarePulseBuffer(context, sampleFrameLength) {
     var audioBuffer = context.createBuffer(1, sampleFrameLength, context.sampleRate);
     var n = audioBuffer.length;
     var data = audioBuffer.getChannelData(0);
     for (var i = 0; i < n; ++i)
         data[i] = 1;
     return audioBuffer;
 }
 // The triangle buffer holds the expected result of the convolution.
 // It linearly ramps up from 0 to its maximum value (at the center)
 // then linearly ramps down to 0.  The center value corresponds to the
 // point where the two square pulses overlap the most.
 function createTrianglePulseBuffer(context, sampleFrameLength) {
     var audioBuffer = context.createBuffer(1, sampleFrameLength, context.sampleRate);
     var n = audioBuffer.length;
     var halfLength = n / 2;
     var data = audioBuffer.getChannelData(0);
     for (var i = 0; i < halfLength; ++i)
         data[i] = i + 1;
     for (var i = halfLength; i < n; ++i)
         data[i] = n - i - 1;
     return audioBuffer;
 }
 function log10(x) {
   return Math.log(x)/Math.LN10;
 }
 function linearToDecibel(x) {
   return 20*log10(x);
 }
 // Verify that the rendered result is very close to the reference
 // triangular pulse.
 function checkTriangularPulse(rendered, reference) {
     var match = true;
     var maxDelta = 0;
     var valueAtMaxDelta = 0;
     var maxDeltaIndex = 0;
     for (var i = 0; i < reference.length; ++i) {
         var diff = rendered[i] - reference[i];
         var x = Math.abs(diff);
         if (x > maxDelta) {
             maxDelta = x;
             valueAtMaxDelta = reference[i];
             maxDeltaIndex = i;
         }
     }
     // allowedDeviationFraction was determined experimentally.  It
     // is the threshold of the relative error at the maximum
     // difference between the true triangular pulse and the
     // rendered pulse.
     var allowedDeviationDecibels = -129.4;
     var maxDeviationDecibels = linearToDecibel(maxDelta / valueAtMaxDelta);
     if (maxDeviationDecibels <= allowedDeviationDecibels) {
         testPassed("Triangular portion of convolution is correct.");
     } else {
         testFailed("Triangular portion of convolution is not correct.  Max deviation = " + maxDeviationDecibels + " dB at " + maxDeltaIndex);
         match = false;
     }
     return match;
 }
 // Verify that the rendered data is close to zero for the first part
 // of the tail.
 function checkTail1(data, reference, breakpoint) {
     var isZero = true;
     var tail1Max = 0;
     for (var i = reference.length; i < reference.length + breakpoint; ++i) {
         var mag = Math.abs(data[i]);
         if (mag > tail1Max) {
             tail1Max = mag;
         }
     }
     // Let's find the peak of the reference (even though we know a
     // priori what it is).
     var refMax = 0;
     for (var i = 0; i < reference.length; ++i) {
       refMax = Math.max(refMax, Math.abs(reference[i]));
     }
     // This threshold is experimentally determined by examining the
     // value of tail1MaxDecibels.
     var threshold1 = -129.7;
     var tail1MaxDecibels = linearToDecibel(tail1Max/refMax);
     if (tail1MaxDecibels <= threshold1) {
         testPassed("First part of tail of convolution is sufficiently small.");
     } else {
         testFailed("First part of tail of convolution is not sufficiently small: " + tail1MaxDecibels + " dB");
         isZero = false;
     }
     return isZero;
 }
 // Verify that the second part of the tail of the convolution is
 // exactly zero.
 function checkTail2(data, reference, breakpoint) {
     var isZero = true;
     var tail2Max = 0;
     // For the second part of the tail, the maximum value should be
     // exactly zero.
     var threshold2 = 0;
     for (var i = reference.length + breakpoint; i < data.length; ++i) {
         if (Math.abs(data[i]) > 0) {
             isZero = false;
             break;
         }
     }
     if (isZero) {
         testPassed("Rendered signal after tail of convolution is silent.");
     } else {
         testFailed("Rendered signal after tail of convolution should be silent.");
     }
     return isZero;
 }
 function checkConvolvedResult(trianglePulse) {
     return function(event) {
         var renderedBuffer = event.renderedBuffer;
         var referenceData = trianglePulse.getChannelData(0);
         var renderedData = renderedBuffer.getChannelData(0);
         var success = true;
         // Verify the triangular pulse is actually triangular.
         success = success && checkTriangularPulse(renderedData, referenceData);
         // Make sure that portion after convolved portion is totally
         // silent.  But round-off prevents this from being completely
         // true.  At the end of the triangle, it should be close to
         // zero.  If we go farther out, it should be even closer and
         // eventually zero.
         // For the tail of the convolution (where the result would be
         // theoretically zero), we partition the tail into two
         // parts.  The first is the at the beginning of the tail,
         // where we tolerate a small but non-zero value.  The second part is
         // farther along the tail where the result should be zero.
         // breakpoint is the point dividing the first two tail parts
         // we're looking at.  Experimentally determined.
         var breakpoint = 12800;
         success = success && checkTail1(renderedData, referenceData, breakpoint);
         success = success && checkTail2(renderedData, referenceData, breakpoint);
         if (success) {
             testPassed("Test signal was correctly convolved.");
         } else {
             testFailed("Test signal was not correctly convolved.");
         }
         finishJSTest();
     }
 }