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<!DOCTYPE html>
<title>Test exponentialRampToValueAtTime() with a large ratio of change</title>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script>
'use strict';
promise_test(async function() {
const sampleRate = 16384;
// not a power of two, so that there is some rounding error in the exponent
const rampEndSample = 255;
const bufferSize = rampEndSample + 1;
const offset0 = 20.;
const offset1 = 20000.;
// Math.pow(2, -23) ~ 1 unit in the last place (ulp).
// Single-precision powf() amplifies rounding error of less than 0.5 ulp in
// to the exponent to more than 2 ulp when the curve spans this large ratio.
// This test is not in upstream wpt because this may be more precision than
// expected from an implementation.
const relativeTolerance = Math.pow(2, -23);
const context = new OfflineAudioContext(1, bufferSize, sampleRate);
const source = new ConstantSourceNode(context);
source.start();
// Explicit event to work around
// https://bugzilla.mozilla.org/show_bug.cgi?id=1265393
source.offset.setValueAtTime(offset0, 0.);
source.offset.exponentialRampToValueAtTime(offset1, rampEndSample/sampleRate);
source.connect(context.destination);
const buffer = await context.startRendering();
assert_equals(buffer.length, bufferSize, "output buffer length");
const output = buffer.getChannelData(0);
const ratio = offset1 / offset0;
for (let i = 0; i < bufferSize; ++i) {
// Math.pow() uses double precision, while `output` has single precision,
// but `tolerance` is enough to accommodate differences.
const expected = offset0 * Math.pow(offset1/offset0, i/rampEndSample);
assert_approx_equals(
output[i],
expected,
relativeTolerance * expected,
"scheduled value at " + i);
}
});
</script>
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