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<!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>
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