1 files changed, 182 insertions, 0 deletions
diff --git a/dom/media/webaudio/test/blink/convolution-testing.js b/dom/media/webaudio/test/blink/convolution-testing.js
new file mode 100644
index 000000000..98ff0c775
--- /dev/null
+++ b/dom/media/webaudio/test/blink/convolution-testing.js
@@ -0,0 +1,182 @@
+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();
+    }
+}