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<head>
<title>
Test Negative AudioParam.exponentialRampToValueAtTime
</title>
<script src="../../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 sampleRate = 48000;
let audit = Audit.createTaskRunner();
audit.define('both negative values', (task, should) => {
let renderDuration = 0.125;
// Create context with two channels. Channel 0 contains the
// positive-valued exponential and channel 1 contains the
// negative-valued exponential. We'll compare the two channels to
// verify that they're the same, as they should be.
let context =
new OfflineAudioContext(2, renderDuration * sampleRate, sampleRate);
let source = context.createBufferSource();
source.buffer = createConstantBuffer(context, 1, 1);
source.loop = true;
// Gain node gp is for the positive-valued exponential ramp, and gn is
// for the negative-valued exponential ramp.
let gp = context.createGain();
let gn = context.createGain();
let merger = context.createChannelMerger(2);
source.connect(gp).connect(merger, 0, 0);
source.connect(gn).connect(merger, 0, 1);
merger.connect(context.destination);
gp.gain.setValueAtTime(1, 0);
gp.gain.exponentialRampToValueAtTime(2, renderDuration);
gn.gain.setValueAtTime(-1, 0);
gn.gain.exponentialRampToValueAtTime(-2, renderDuration);
source.start();
context.startRendering()
.then(function(resultBuffer) {
// Verify that channels have the same values, except for the sign.
let expected = resultBuffer.getChannelData(0);
let actual = resultBuffer.getChannelData(1);
let inverted = expected.map(sample => -sample);
should(actual, 'Negative exponential ramp from -1 to -2')
.beEqualToArray(inverted);
})
.then(() => task.done());
});
audit.define('negative-end', (task, should) => {
// Positive start value and negative end value should just do nothing.
let renderDuration = 0.125;
let context =
new OfflineAudioContext(1, renderDuration * sampleRate, sampleRate);
let source = context.createBufferSource();
source.buffer = createConstantBuffer(context, 1, 1);
source.loop = true;
// Gain node gp is for the positive-valued exponential ramp, and gn is
// for the negative-valued exponential ramp.
let g = context.createGain();
g.gain.setValueAtTime(2, 0);
g.gain.exponentialRampToValueAtTime(-1, renderDuration);
source.connect(g).connect(context.destination);
source.start();
context.startRendering()
.then(function(resultBuffer) {
let actual = resultBuffer.getChannelData(0);
should(actual, 'Exponential ramp from 2 to -1')
.beConstantValueOf(2);
})
.then(() => task.done());
});
audit.define('positive-end', (task, should) => {
// Positive start value and negative end value should just do nothing.
let renderDuration = 0.125;
let context =
new OfflineAudioContext(1, renderDuration * sampleRate, sampleRate);
let source = context.createBufferSource();
source.buffer = createConstantBuffer(context, 1, 1);
source.loop = true;
let g = context.createGain();
g.gain.setValueAtTime(-1, 0);
g.gain.exponentialRampToValueAtTime(1, renderDuration);
source.connect(g).connect(context.destination);
source.start();
context.startRendering()
.then(function(resultBuffer) {
let actual = resultBuffer.getChannelData(0);
should(actual, 'Exponential ramp from -1 to 1')
.beConstantValueOf(-1);
})
.then(() => task.done());
});
audit.define('propagate', (task, should) => {
// Test propagation of ramp if the exponential ramp start and end values
// have opposite sign.
let renderDuration = 0.125;
let linearRampEnd = renderDuration / 4;
let exponentialRampEnd = renderDuration / 2;
let context =
new OfflineAudioContext(1, renderDuration * sampleRate, sampleRate);
let source = context.createBufferSource();
source.buffer = createConstantBuffer(context, 1, 1);
source.loop = true;
let g = context.createGain();
g.gain.setValueAtTime(2, 0);
g.gain.linearRampToValueAtTime(-1, linearRampEnd);
g.gain.exponentialRampToValueAtTime(1, exponentialRampEnd);
source.connect(g).connect(context.destination);
source.start();
context.startRendering()
.then(function(resultBuffer) {
let actual = resultBuffer.getChannelData(0);
// Since the start value of the exponential ramp is -1 and the end
// value is 1, the ramp should just propagate -1 to the end of
// the exponential ramp, and then propagate the exponential ramp
// value "forever" afterwards.
const linearEndFrame = Math.ceil(linearRampEnd * sampleRate);
const expoEndFrame = Math.ceil(exponentialRampEnd * sampleRate);
should(
actual.slice(linearEndFrame, expoEndFrame),
'Exponential ramp from -1 to 1 after the end of the linear ramp')
.beConstantValueOf(-1);
should(
actual.slice(expoEndFrame),
'Exponential ramp after end of ramp')
.beConstantValueOf(1);
})
.then(() => task.done());
});
audit.run();
</script>
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