third_party/WebKit/LayoutTests/webaudio/audiobuffer-resample.html

   1 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
   2 <html>
   3   <head>
   4     <script src="resources/compatibility.js"></script>
   5     <script src="resources/audio-testing.js"></script>
   6     <script src="../resources/js-test.js"></script>
   7   </head>
   8
   9   <body>
  10     <div id="description"></div>
  11     <div id="console"></div>
  12
  13     <script>
  14       // These are global to make debugging a little easier.
  15       var context;
  16       var buffer;
  17       var source;
  18       var renderedData;
  19       var trueData;
  20       var signalEnergy;
  21       var noiseEnergy;
  22       var maxError;
  23
  24       // Context sample rate.
  25       var sampleRate = 48000;
  26       // The sample rate of the buffer.
  27       var bufferRate = 3000;
  28       // The audio buffer is a sine wave of this frequency.
  29       var toneFrequency = 440;
  30       // How long test is
  31       var lengthInSeconds = 0.5;
  32       // The maximum allowed peak error between the actual and true output. This value was
  33       // experimentally determined for the given bufferRate.
  34       var peakThreshold = 0.11;
  35       // The minimum SNR allowed between the actual and true output.
  36       var snrThreshold = 22.35;
  37
  38       description("Test resampling of an AudioBuffer at " + bufferRate + " Hz");
  39
  40       function log10(x) {
  41           return Math.log(x)/Math.LN10;
  42       }
  43
  44       // Generate a sine wave in an AudioBuffer using the given |freq|. The AudioBuffer has the
  45       // sample rate of |rate|.
  46       function createSineBuffer(context, freq, rate) {
  47           var buf = context.createBuffer(1, lengthInSeconds * rate, rate);
  48           var omega = 2 * Math.PI * freq / rate;
  49           var signal = buf.getChannelData(0);
  50           var length = signal.length;
  51           for (var k = 0; k < length; ++k)
  52             signal[k] = Math.sin(omega * k);
  53
  54           return buf;
  55       }
  56
  57       // Check the output against the expected output.
  58       function checkResult(event) {
  59           renderedData = event.renderedBuffer.getChannelData(0);
  60           var length = renderedData.length;
  61           // Generate a reference sine wave at the context rate
  62           var trueReference = createSineBuffer(context, toneFrequency, context.sampleRate);
  63           trueData = trueReference.getChannelData(0);
  64
  65           // To compare the actual output against the reference, we compute the peak error and the
  66           // SNR between the two.
  67           signalEnergy = 0;
  68           noiseEnergy = 0;
  69           maxError = -1;
  70
  71           var success = true;
  72
  73           // Compute the peak error and the SNR.
  74           for (var k = 0; k < length / 2; ++k) {
  75               var diff = renderedData[k] - trueData[k];
  76               noiseEnergy += diff * diff;
  77               signalEnergy += trueData[k] * trueData[k];
  78               if (Math.abs(diff) > maxError)
  79                   maxError = Math.abs(diff);
  80           }
  81
  82           var snr;
  83
  84           if (noiseEnergy == 0)
  85               snr = 1000;
  86           else
  87               snr = 10 * log10(signalEnergy / noiseEnergy);
  88
  89           if (maxError < peakThreshold) {
  90               testPassed("Peak error between actual and reference data below threshold of " +
  91                          peakThreshold + ".");
  92           } else {
  93               testFailed("Peak error of " + maxError + " exceeds threshold of " +
  94                          peakThreshold + ".");
  95               success = false;
  96           }
  97
  98           if (snr > snrThreshold) {
  99               testPassed("SNR exceeds threshold of " + snrThreshold + " dB.");
 100           } else {
 101               testFailed("SNR of " + snr + " is below the threshold of " + snrThreshold + ".");
 102               success = false;
 103           }
 104
 105           if (success)
 106               testPassed("AudioBuffer resampling is accurate for buffer rate of " +
 107                          bufferRate + " Hz.");
 108           else
 109               testFailed("AudioBuffer resampling is not accurate enough for buffer rate of " +
 110                          bufferRate + " Hz.");
 111
 112           finishJSTest();
 113       }
 114
 115       function runTest() {
 116           if (window.testRunner) {
 117               testRunner.dumpAsText();
 118               testRunner.waitUntilDone();
 119           }
 120
 121           window.jsTestIsAsync = true;
 122
 123           context = new OfflineAudioContext(1, lengthInSeconds * sampleRate, sampleRate);
 124
 125           // Create a sine wave in a buffer that's different from the context rate to test
 126           // resampling.
 127           buffer = createSineBuffer(context, toneFrequency, bufferRate);
 128           source = context.createBufferSource();
 129           source.buffer = buffer;
 130           source.connect(context.destination);
 131           source.start();
 132
 133           context.oncomplete = checkResult;
 134           context.startRendering();
 135       }
 136       runTest();
 137       successfullyParsed = true;
 138     </script>
 139   </body>
 140 </html>