| <!DOCTYPE html> |
| <html> |
| <head> |
| <title> |
| audiobuffer-resample.html |
| </title> |
| <script src="../../imported/w3c/web-platform-tests/resources/testharness.js"></script> |
| <script src="../../resources/testharnessreport.js"></script> |
| <script src="../resources/audit-util.js"></script> |
| <script src="../resources/audit.js"></script> |
| </head> |
| <body> |
| <script id="layout-test-code"> |
| let audit = Audit.createTaskRunner(); |
| |
| // These are global to make debugging a little easier. |
| let context; |
| let buffer; |
| let source; |
| let renderedData; |
| let trueData; |
| let signalEnergy; |
| let noiseEnergy; |
| let maxError; |
| |
| // Context sample rate. |
| let sampleRate = 48000; |
| // The sample rate of the buffer. |
| let bufferRate = 3000; |
| // The audio buffer is a sine wave of this frequency. |
| let toneFrequency = 440; |
| // How long test is |
| let lengthInSeconds = 0.5; |
| // The maximum allowed peak error between the actual and true output. This |
| // value was experimentally determined for the given bufferRate. |
| let peakThreshold = 0.11; |
| // The minimum SNR allowed between the actual and true output. |
| let snrThreshold = 22.35; |
| |
| |
| // Generate a sine wave in an AudioBuffer using the given |freq|. The |
| // AudioBuffer has the sample rate of |rate|. |
| function createSineBuffer(context, freq, rate) { |
| let buf = context.createBuffer(1, lengthInSeconds * rate, rate); |
| let omega = 2 * Math.PI * freq / rate; |
| let signal = buf.getChannelData(0); |
| let length = signal.length; |
| for (let k = 0; k < length; ++k) |
| signal[k] = Math.sin(omega * k); |
| |
| return buf; |
| } |
| |
| // Check the output against the expected output. |
| function checkResult(buffer, should) { |
| renderedData = buffer.getChannelData(0); |
| let length = renderedData.length; |
| // Generate a reference sine wave at the context rate |
| let 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; |
| |
| let success = true; |
| |
| // Compute the peak error and the SNR. |
| for (let k = 0; k < length / 2; ++k) { |
| let diff = renderedData[k] - trueData[k]; |
| noiseEnergy += diff * diff; |
| signalEnergy += trueData[k] * trueData[k]; |
| if (Math.abs(diff) > maxError) |
| maxError = Math.abs(diff); |
| } |
| |
| let snr; |
| |
| if (noiseEnergy == 0) |
| snr = 1000; |
| else |
| snr = 10 * Math.log10(signalEnergy / noiseEnergy); |
| |
| should(maxError, 'Peak error between actual and reference data') |
| .beLessThan(peakThreshold); |
| |
| should(snr, 'SNR').beGreaterThan(snrThreshold); |
| } |
| |
| audit.define('Test resampling of an AudioBuffer', function(task, should) { |
| 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.startRendering() |
| .then(function(buffer) { |
| checkResult(buffer, should); |
| }) |
| .then(task.done.bind(task)); |
| }); |
| |
| audit.run(); |
| </script> |
| </body> |
| </html> |
