| <!doctype html> |
| <html> |
| <head> |
| <title>Test Extrapolation at end of AudibBuffer in an AudioBufferSourceNode</title> |
| <script src="/resources/testharness.js"></script> |
| <script src="/resources/testharnessreport.js"></script> |
| <script src="/webaudio/resources/audit-util.js"></script> |
| <script src="/webaudio/resources/audit.js"></script> |
| </head> |
| <body> |
| <script> |
| let audit = Audit.createTaskRunner(); |
| |
| const sampleRate = 48000; |
| |
| // For testing we only need a few render quanta. |
| const renderSamples = 512 |
| |
| // Sample rate for our buffers. This is the lowest sample rate that is |
| // required to be supported. |
| const bufferRate = 8000; |
| |
| // Number of samples in each AudioBuffer; this is fairly arbitrary but |
| // should be less than a render quantum. |
| const bufferLength = 30; |
| |
| // Frequency of the sine wave for testing. |
| const frequency = 440; |
| |
| audit.define( |
| { |
| label: 'interpolate', |
| description: 'Interpolation of AudioBuffers to context sample rate' |
| }, |
| (task, should) => { |
| // The first channel is for the interpolated signal, and the second |
| // channel is for the reference signal from an oscillator. |
| let context = new OfflineAudioContext({ |
| numberOfChannels: 2, |
| length: renderSamples, |
| sampleRate: sampleRate |
| }); |
| |
| let merger = new ChannelMergerNode( |
| context, {numberOfChannels: context.destination.channelCount}); |
| merger.connect(context.destination); |
| |
| // Create a set of AudioBuffers which are samples from a pure sine |
| // wave with frequency |frequency|. |
| const nBuffers = Math.floor(context.length / bufferLength); |
| const omega = 2 * Math.PI * frequency / bufferRate; |
| |
| let frameNumber = 0; |
| let startTime = 0; |
| |
| for (let k = 0; k < nBuffers; ++k) { |
| // let buffer = context.createBuffer(1, bufferLength, |
| // bufferRate); |
| let buffer = new AudioBuffer( |
| {length: bufferLength, sampleRate: bufferRate}); |
| let data = buffer.getChannelData(0); |
| for (let n = 0; n < bufferLength; ++n) { |
| data[n] = Math.sin(omega * frameNumber); |
| ++frameNumber; |
| } |
| // Create a source using this buffer and start it at the end of |
| // the previous buffer. |
| let src = new AudioBufferSourceNode(context, {buffer: buffer}); |
| |
| src.connect(merger, 0, 0); |
| src.start(startTime); |
| startTime += buffer.duration; |
| } |
| |
| // Create the reference sine signal using an oscillator. |
| let osc = new OscillatorNode( |
| context, {type: 'sine', frequency: frequency}); |
| osc.connect(merger, 0, 1); |
| osc.start(0); |
| |
| context.startRendering() |
| .then(audioBuffer => { |
| let actual = audioBuffer.getChannelData(0); |
| let expected = audioBuffer.getChannelData(1); |
| |
| should(actual, 'Interpolated sine wave') |
| .beCloseToArray(expected, {absoluteThreshold: 9.0348e-2}); |
| |
| // Compute SNR between them. |
| let snr = 10 * Math.log10(computeSNR(actual, expected)); |
| |
| should(snr, `SNR (${snr.toPrecision(4)} dB)`) |
| .beGreaterThanOrEqualTo(37.17); |
| }) |
| .then(() => task.done()); |
| }); |
| |
| audit.run(); |
| </script> |
| </body> |
| </html> |
