| <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> |
| <html> |
| <head> |
| <script src="resources/compatibility.js"></script> |
| <script src="resources/audio-testing.js"></script> |
| <script src="../resources/js-test.js"></script> |
| </head> |
| |
| <body> |
| <div id="description"></div> |
| <div id="console"></div> |
| |
| <script> |
| // These are global to make debugging a little easier. |
| var context; |
| var buffer; |
| var source; |
| var renderedData; |
| var trueData; |
| var signalEnergy; |
| var noiseEnergy; |
| var maxError; |
| |
| // Context sample rate. |
| var sampleRate = 48000; |
| // The sample rate of the buffer. |
| var bufferRate = 3000; |
| // The audio buffer is a sine wave of this frequency. |
| var toneFrequency = 440; |
| // How long test is |
| var lengthInSeconds = 0.5; |
| // The maximum allowed peak error between the actual and true output. This value was |
| // experimentally determined for the given bufferRate. |
| var peakThreshold = 0.11; |
| // The minimum SNR allowed between the actual and true output. |
| var snrThreshold = 22.35; |
| |
| description("Test resampling of an AudioBuffer at " + bufferRate + " Hz"); |
| |
| function log10(x) { |
| return Math.log(x)/Math.LN10; |
| } |
| |
| // Generate a sine wave in an AudioBuffer using the given |freq|. The AudioBuffer has the |
| // sample rate of |rate|. |
| function createSineBuffer(context, freq, rate) { |
| var buf = context.createBuffer(1, lengthInSeconds * rate, rate); |
| var omega = 2 * Math.PI * freq / rate; |
| var signal = buf.getChannelData(0); |
| var length = signal.length; |
| for (var k = 0; k < length; ++k) |
| signal[k] = Math.sin(omega * k); |
| |
| return buf; |
| } |
| |
| // Check the output against the expected output. |
| function checkResult(event) { |
| renderedData = event.renderedBuffer.getChannelData(0); |
| var length = renderedData.length; |
| // Generate a reference sine wave at the context rate |
| var trueReference = createSineBuffer(context, toneFrequency, context.sampleRate); |
| trueData = trueReference.getChannelData(0); |
| |
| // To compare the actual output against the reference, we compute the peak error and the |
| // SNR between the two. |
| signalEnergy = 0; |
| noiseEnergy = 0; |
| maxError = -1; |
| |
| var success = true; |
| |
| // Compute the peak error and the SNR. |
| for (var k = 0; k < length / 2; ++k) { |
| var diff = renderedData[k] - trueData[k]; |
| noiseEnergy += diff * diff; |
| signalEnergy += trueData[k] * trueData[k]; |
| if (Math.abs(diff) > maxError) |
| maxError = Math.abs(diff); |
| } |
| |
| var snr; |
| |
| if (noiseEnergy == 0) |
| snr = 1000; |
| else |
| snr = 10 * log10(signalEnergy / noiseEnergy); |
| |
| if (maxError < peakThreshold) { |
| testPassed("Peak error between actual and reference data below threshold of " + |
| peakThreshold + "."); |
| } else { |
| testFailed("Peak error of " + maxError + " exceeds threshold of " + |
| peakThreshold + "."); |
| success = false; |
| } |
| |
| if (snr > snrThreshold) { |
| testPassed("SNR exceeds threshold of " + snrThreshold + " dB."); |
| } else { |
| testFailed("SNR of " + snr + " is below the threshold of " + snrThreshold + "."); |
| success = false; |
| } |
| |
| if (success) |
| testPassed("AudioBuffer resampling is accurate for buffer rate of " + |
| bufferRate + " Hz."); |
| else |
| testFailed("AudioBuffer resampling is not accurate enough for buffer rate of " + |
| bufferRate + " Hz."); |
| |
| finishJSTest(); |
| } |
| |
| function runTest() { |
| if (window.testRunner) { |
| testRunner.dumpAsText(); |
| testRunner.waitUntilDone(); |
| } |
| |
| window.jsTestIsAsync = true; |
| |
| context = new OfflineAudioContext(1, lengthInSeconds * sampleRate, sampleRate); |
| |
| // Create a sine wave in a buffer that's different from the context rate to test |
| // resampling. |
| buffer = createSineBuffer(context, toneFrequency, bufferRate); |
| source = context.createBufferSource(); |
| source.buffer = buffer; |
| source.connect(context.destination); |
| source.start(); |
| |
| context.oncomplete = checkResult; |
| context.startRendering(); |
| } |
| runTest(); |
| successfullyParsed = true; |
| </script> |
| </body> |
| </html> |
