Implement IIRFilter node for WebAudio.

third_party/WebKit/LayoutTests/webaudio/resources/biquad-filters.js

Index: third_party/WebKit/LayoutTests/webaudio/resources/biquad-filters.js
diff --git a/third_party/WebKit/LayoutTests/webaudio/resources/biquad-testing.js b/third_party/WebKit/LayoutTests/webaudio/resources/biquad-filters.js
similarity index 60%
copy from third_party/WebKit/LayoutTests/webaudio/resources/biquad-testing.js
copy to third_party/WebKit/LayoutTests/webaudio/resources/biquad-filters.js
index 8d8077ba12d7b037497f3a32918bb849bdfde97b..c2517694218bcc5408b09ed4107dc6d0d121cfce 100644
--- a/third_party/WebKit/LayoutTests/webaudio/resources/biquad-testing.js
+++ b/third_party/WebKit/LayoutTests/webaudio/resources/biquad-filters.js
@@ -1,33 +1,3 @@
-// Globals, to make testing and debugging easier.
-var context;
-var filter;
-var signal;
-var renderedBuffer;
-var renderedData;
-
-var sampleRate = 44100.0;
-var pulseLengthFrames = .1 * sampleRate;
-
-// Maximum allowed error for the test to succeed.  Experimentally determined. 
-var maxAllowedError = 5.9e-8;
-
-// This must be large enough so that the filtered result is
-// essentially zero.  See comments for createTestAndRun.
-var timeStep = .1;
-
-// Maximum number of filters we can process (mostly for setting the
-// render length correctly.)
-var maxFilters = 5;
-
-// How long to render.  Must be long enough for all of the filters we
-// want to test.
-var renderLengthSeconds = timeStep * (maxFilters + 1) ;
-
-var renderLengthSamples = Math.round(renderLengthSeconds * sampleRate);
-
-// Number of filters that will be processed.
-var nFilters;
-
 // A biquad filter has a z-transform of
 // H(z) = (b0 + b1 / z + b2 / z^2) / (1 + a1 / z + a2 / z^2)
 //
@@ -156,7 +126,7 @@ function createBandpassFilter(freq, q, gain) {
         // independent of q.
         coef = {b0 : 0, b1 : 0, b2 : 0, a1 : 0, a2 : 0}
     }
-  
+
     return coef;
 }
 
@@ -169,16 +139,16 @@ function createLowShelfFilter(freq, q, gain) {
     var a1;
     var a2;
     var coef;
-  
+
     var S = 1;
     var A = Math.pow(10, gain / 40);
 
     if (freq == 1) {
         // The filter is just a constant gain
-        coef = {b0 : A * A, b1 : 0, b2 : 0, a1 : 0, a2 : 0};  
+        coef = {b0 : A * A, b1 : 0, b2 : 0, a1 : 0, a2 : 0};
     } else if (freq == 0) {
         // The filter is 1
-        coef = {b0 : 1, b1 : 0, b2 : 0, a1 : 0, a2 : 0};  
+        coef = {b0 : 1, b1 : 0, b2 : 0, a1 : 0, a2 : 0};
     } else {
         var w0 = Math.PI * freq;
         var alpha = 1 / 2 * Math.sin(w0) * Math.sqrt((A + 1 / A) * (1 / S - 1) + 2);
@@ -262,7 +232,7 @@ function createPeakingFilter(freq, q, gain) {
             a0 = 1 + alpha / A;
             a1 = -2 * k;
             a2 = 1 - alpha / A;
-  
+
             coef = normalizeFilterCoefficients(b0, b1, b2, a0, a1, a2);
         } else {
             // q = 0, we have a divide by zero problem in the formulas
@@ -347,30 +317,6 @@ function createAllpassFilter(freq, q, gain) {
     return coef;
 }
 
-// Map the filter type name to a function that computes the filter coefficents for the given filter
-// type.
-var filterCreatorFunction = {"lowpass": createLowpassFilter,
-                             "highpass": createHighpassFilter,
-                             "bandpass": createBandpassFilter,
-                             "lowshelf": createLowShelfFilter,
-                             "highshelf": createHighShelfFilter,
-                             "peaking": createPeakingFilter,
-                             "notch": createNotchFilter,
-                             "allpass": createAllpassFilter};
-
-var filterTypeName = {"lowpass": "Lowpass filter",
-                      "highpass": "Highpass filter",
-                      "bandpass": "Bandpass filter",
-                      "lowshelf": "Lowshelf filter",
-                      "highshelf": "Highshelf filter",
-                      "peaking": "Peaking filter",
-                      "notch": "Notch filter",
-                      "allpass": "Allpass filter"};
-
-function createFilter(filterType, freq, q, gain) {
-    return filterCreatorFunction[filterType](freq, q, gain);
-}
-
 function filterData(filterCoef, signal, len) {
     var y = new Array(len);
     var b0 = filterCoef.b0;
@@ -397,152 +343,26 @@ function filterData(filterCoef, signal, len) {
     return y;
 }
 
-function createImpulseBuffer(context, length) {
-    var impulse = context.createBuffer(1, length, context.sampleRate);
-    var data = impulse.getChannelData(0);
-    for (var k = 1; k < data.length; ++k) {
-        data[k] = 0;
-    }
-    data[0] = 1;
-
-    return impulse;
-}
-
-
-function createTestAndRun(context, filterType, filterParameters) {
-    // To test the filters, we apply a signal (an impulse) to each of
-    // the specified filters, with each signal starting at a different
-    // time.  The output of the filters is summed together at the
-    // output.  Thus for filter k, the signal input to the filter
-    // starts at time k * timeStep.  For this to work well, timeStep
-    // must be large enough for the output of each filter to have
-    // decayed to zero with timeStep seconds.  That way the filter
-    // outputs don't interfere with each other.
-    
-    nFilters = Math.min(filterParameters.length, maxFilters);
-
-    signal = new Array(nFilters);
-    filter = new Array(nFilters);
-
-    impulse = createImpulseBuffer(context, pulseLengthFrames);
-
-    // Create all of the signal sources and filters that we need.
-    for (var k = 0; k < nFilters; ++k) {
-        signal[k] = context.createBufferSource();
-        signal[k].buffer = impulse;
-
-        filter[k] = context.createBiquadFilter();
-        filter[k].type = filterType;
-        filter[k].frequency.value = context.sampleRate / 2 * filterParameters[k].cutoff;
-        filter[k].detune.value = (filterParameters[k].detune === undefined) ? 0 : filterParameters[k].detune;
-        filter[k].Q.value = filterParameters[k].q;
-        filter[k].gain.value = filterParameters[k].gain;
-
-        signal[k].connect(filter[k]);
-        filter[k].connect(context.destination);
-
-        signal[k].start(timeStep * k);
-    }
-
-    context.oncomplete = checkFilterResponse(filterType, filterParameters);
-    context.startRendering();
-}
-
-function addSignal(dest, src, destOffset) {
-    // Add src to dest at the given dest offset.
-    for (var k = destOffset, j = 0; k < dest.length, j < src.length; ++k, ++j) {
-        dest[k] += src[j];
-    }
-}
-
-function generateReference(filterType, filterParameters) {
-    var result = new Array(renderLengthSamples);
-    var data = new Array(renderLengthSamples);
-    // Initialize the result array and data.
-    for (var k = 0; k < result.length; ++k) {
-        result[k] = 0;
-        data[k] = 0;
-    }
-    // Make data an impulse.
-    data[0] = 1;
-    
-    for (var k = 0; k < nFilters; ++k) {
-        // Filter an impulse
-        var detune = (filterParameters[k].detune === undefined) ? 0 : filterParameters[k].detune;
-        var frequency = filterParameters[k].cutoff * Math.pow(2, detune / 1200); // Apply detune, converting from Cents.
-        
-        var filterCoef = createFilter(filterType,
-                                      frequency,
-                                      filterParameters[k].q,
-                                      filterParameters[k].gain);
-        var y = filterData(filterCoef, data, renderLengthSamples);
-
-        // Accumulate this filtered data into the final output at the desired offset.
-        addSignal(result, y, timeToSampleFrame(timeStep * k, sampleRate));
-    }
-
-    return result;
-}
-
-function checkFilterResponse(filterType, filterParameters) {
-    return function(event) {
-        renderedBuffer = event.renderedBuffer;
-        renderedData = renderedBuffer.getChannelData(0);
-
-        reference = generateReference(filterType, filterParameters);
-        
-        var len = Math.min(renderedData.length, reference.length);
-
-        var success = true;
-
-        // Maximum error between rendered data and expected data
-        var maxError = 0;
-
-        // Sample offset where the maximum error occurred.
-        var maxPosition = 0;
-
-        // Number of infinities or NaNs that occurred in the rendered data.
-        var invalidNumberCount = 0;
-
-        if (nFilters != filterParameters.length) {
-            testFailed("Test wanted " + filterParameters.length + " filters but only " + maxFilters + " allowed.");
-            success = false;
-        }
+// Map the filter type name to a function that computes the filter coefficents for the given filter
+// type.
+var filterCreatorFunction = {"lowpass": createLowpassFilter,
+                             "highpass": createHighpassFilter,
+                             "bandpass": createBandpassFilter,
+                             "lowshelf": createLowShelfFilter,
+                             "highshelf": createHighShelfFilter,
+                             "peaking": createPeakingFilter,
+                             "notch": createNotchFilter,
+                             "allpass": createAllpassFilter};
 
-        // Compare the rendered signal with our reference, keeping
-        // track of the maximum difference (and the offset of the max
-        // difference.)  Check for bad numbers in the rendered output
-        // too.  There shouldn't be any.
-        for (var k = 0; k < len; ++k) {
-            var err = Math.abs(renderedData[k] - reference[k]);
-            if (err > maxError) {
-                maxError = err;
-                maxPosition = k;
-            }
-            if (!isValidNumber(renderedData[k])) {
-                ++invalidNumberCount;
-            }
-        }
+var filterTypeName = {"lowpass": "Lowpass filter",
+                      "highpass": "Highpass filter",
+                      "bandpass": "Bandpass filter",
+                      "lowshelf": "Lowshelf filter",
+                      "highshelf": "Highshelf filter",
+                      "peaking": "Peaking filter",
+                      "notch": "Notch filter",
+                      "allpass": "Allpass filter"};
 
-        if (invalidNumberCount > 0) {
-            testFailed("Rendered output has " + invalidNumberCount + " infinities or NaNs.");
-            success = false;
-        } else {
-            testPassed("Rendered output did not have infinities or NaNs.");
-        }
-        
-        if (maxError <= maxAllowedError) {
-            testPassed(filterTypeName[filterType] + " response is correct.");
-        } else {
-            testFailed(filterTypeName[filterType] + " response is incorrect.  Max err = " + maxError + " at " + maxPosition + ".  Threshold = " + maxAllowedError);
-            success = false;
-        }
-        
-        if (success) {
-            testPassed("Test signal was correctly filtered.");
-        } else {
-            testFailed("Test signal was not correctly filtered.");
-        }
-        finishJSTest();
-    }
+function createFilter(filterType, freq, q, gain) {
+    return filterCreatorFunction[filterType](freq, q, gain);
 }