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Test Info:
- This WPT test may be referenced by the following Test IDs:
- /webaudio/the-audio-api/the-audiobuffersourcenode-interface/audiobuffersource-loop-continuous.html - WPT Dashboard Interop Dashboard
<!DOCTYPE html>
<html>
<head>
<title>
Test AudioBufferSourceNode Continuous Looping With Unaligned Buffers
</title>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
</head>
<body>
<script>
promise_test(
async () => {
const sampleRate = 48000;
// 65,201 frames produces IEEE-754 roundoff residue when converting
// between sample frames and seconds at 48 kHz:
// (65201 / 48000) * 48000 != 65201.
const bufferLength = 65201;
const loopIterations = 2;
const totalRenderFrames = bufferLength * loopIterations;
const context =
new OfflineAudioContext(1, totalRenderFrames, sampleRate);
const buffer = new AudioBuffer({
numberOfChannels: 1,
length: bufferLength,
sampleRate: sampleRate,
});
const channelData = buffer.getChannelData(0);
for (let i = 0; i < bufferLength; ++i) {
// Normalize to [0.1, 0.9] to avoid clipping or zero-crossing.
channelData[i] = 0.1 + 0.8 * (i / (bufferLength - 1));
}
const source = context.createBufferSource();
source.buffer = buffer;
source.loop = true;
let onendedFired = false;
source.onended = () => {
onendedFired = true;
};
source.connect(context.destination);
source.start();
const renderedBuffer = await context.startRendering();
const output = renderedBuffer.getChannelData(0);
assert_false(
onendedFired,
"onended event must not fire for an indefinitely looping source"
);
// Verify audio does not fall silent or drop samples across cycles.
for (let iter = 0; iter < loopIterations; ++iter) {
const boundarySampleBeforeWrap =
output[iter * bufferLength + bufferLength - 1];
assert_approx_equals(
boundarySampleBeforeWrap,
0.9,
1e-4,
`Sample immediately before wrap in iteration ${iter} ` +
`must match end of buffer`
);
if (iter + 1 < loopIterations) {
const boundarySampleAfterWrap =
output[(iter + 1) * bufferLength];
assert_approx_equals(
boundarySampleAfterWrap,
0.1,
1e-4,
`Sample immediately after wrap in iteration ${iter + 1} ` +
`must match start of buffer`
);
}
}
},
"Indefinite looping on unaligned buffer (65,201 frames) " +
"renders continuously without stopping or firing onended"
);
promise_test(
async () => {
const sampleRate = 48000;
const bufferLength = 1000;
// Duration specifies 2.5 buffer iterations of total output.
const durationSeconds = (bufferLength * 2.5) / sampleRate;
const totalRenderFrames = bufferLength * 4;
const context =
new OfflineAudioContext(1, totalRenderFrames, sampleRate);
const buffer = new AudioBuffer({
numberOfChannels: 1,
length: bufferLength,
sampleRate: sampleRate,
});
const channelData = buffer.getChannelData(0);
channelData.fill(0.5);
const source = context.createBufferSource();
source.buffer = buffer;
source.loop = true;
source.connect(context.destination);
source.start(0, 0, durationSeconds);
const renderedBuffer = await context.startRendering();
const output = renderedBuffer.getChannelData(0);
const expectedPlayedFrames =
Math.round(durationSeconds * sampleRate);
const expectedActive =
new Float32Array(expectedPlayedFrames).fill(0.5);
assert_array_approx_equals(
output.subarray(0, expectedPlayedFrames),
expectedActive,
1e-4,
"Frames within duration must be active"
);
const remainingFrames = totalRenderFrames - expectedPlayedFrames;
const expectedSilent = new Float32Array(remainingFrames).fill(0);
assert_array_equals(
output.subarray(expectedPlayedFrames),
expectedSilent,
"Frames after duration must be silent"
);
},
"Looping source with explicit grain duration plays exact buffer " +
"duration and terminates"
);
const granularities = [
{
length: 67,
rate: 48000,
iterations: 5,
desc: "sub-quantum prime (67 frames)",
},
{
length: 129,
rate: 48000,
iterations: 3,
desc: "quantum + 1 boundary (129 frames)",
},
{
length: 1486,
rate: 48000,
iterations: 2,
desc: "LAME padding size from crbug.com/553218226 (1,486 frames)",
},
];
for (const config of granularities) {
promise_test(
async () => {
const sampleRate = config.rate;
const bufferLength = config.length;
const loopIterations = config.iterations;
const totalRenderFrames = bufferLength * loopIterations;
const context =
new OfflineAudioContext(1, totalRenderFrames, sampleRate);
const buffer = new AudioBuffer({
numberOfChannels: 1,
length: bufferLength,
sampleRate: sampleRate,
});
const channelData = buffer.getChannelData(0);
for (let i = 0; i < bufferLength; ++i) {
channelData[i] = 0.1 + 0.8 * (i / (bufferLength - 1));
}
const source = context.createBufferSource();
source.buffer = buffer;
source.loop = true;
let onendedFired = false;
source.onended = () => {
onendedFired = true;
};
source.connect(context.destination);
source.start();
const renderedBuffer = await context.startRendering();
const output = renderedBuffer.getChannelData(0);
assert_false(
onendedFired,
`onended must not fire for ${config.desc}`
);
for (let iter = 0; iter < loopIterations; ++iter) {
const beforeWrap = output[iter * bufferLength + bufferLength - 1];
assert_approx_equals(
beforeWrap,
0.9,
1e-4,
`Sample before wrap in iteration ${iter} for ${config.desc}`
);
if (iter + 1 < loopIterations) {
const afterWrap = output[(iter + 1) * bufferLength];
assert_approx_equals(
afterWrap,
0.1,
1e-4,
`Sample after wrap in iteration ${iter + 1} for ` +
`${config.desc}`
);
}
}
},
`Continuous looping on ${config.desc} at ${config.rate} Hz ` +
`renders seamlessly`
);
}
</script>
</body>
</html>