audiobuffersource-playbackrate-dynamic-direction.html

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This test has a WPT meta file that expects 2 subtest issues.
This WPT test may be referenced by the following Test IDs:
- /webaudio/the-audio-api/the-audiobuffersourcenode-interface/audiobuffersource-playbackrate-dynamic-direction.html - WPT Dashboard Interop Dashboard

<!DOCTYPE html>

<html>

<head>

<title>AudioBufferSourceNode Dynamic PlaybackRate Direction</title>

<script src="/resources/testharness.js"></script>

<script src="/resources/testharnessreport.js"></script>

</head>

<body>

<script>

promise_test(async () => {

    let context = new OfflineAudioContext(1, 256, 44100);

    let buffer = context.createBuffer(1, 256, 44100);

    let data = buffer.getChannelData(0);

    for (let i = 0; i < 256; ++i) {

        data[i] = i;

    let source = context.createBufferSource();

    source.buffer = buffer;

    source.playbackRate.setValueAtTime(-1.0, 0);

    // flip to positive halfway (at quantum boundary)

    source.playbackRate.setValueAtTime(1.0, 128 / 44100);

    source.connect(context.destination);

    source.start(0, 255);

    let renderedBuffer = await context.startRendering();

    let renderedData = renderedBuffer.getChannelData(0);

    // Initial direction is negative (-1.0).

    // T=0 to T=127: playhead goes 255 down to 128.

    assert_equals(renderedData[0], 255, 'Frame 0 (negative rate)');

    assert_equals(renderedData[127], 128, 'Frame 127 (negative rate)');

    // Flip to positive (1.0) at T=128.

    // T=128 to T=255: playhead goes 127 up to 254.

    assert_equals(renderedData[128], 127, 'Frame 128 (positive rate)');

    assert_equals(renderedData[255], 254, 'Frame 255 (positive rate)');

}, 'Dynamic direction switch negative to positive honors duration');

promise_test(async () => {

    let context = new OfflineAudioContext(1, 256, 44100);

    let buffer = context.createBuffer(1, 256, 44100);

    let data = buffer.getChannelData(0);

    for (let i = 0; i < 256; ++i) {

        data[i] = i;

    let source = context.createBufferSource();

    source.buffer = buffer;

    source.playbackRate.setValueAtTime(1.0, 0);

    // flip to negative halfway (at quantum boundary)

    source.playbackRate.setValueAtTime(-1.0, 128 / 44100);

    source.connect(context.destination);

    source.start(0, 0);

    let renderedBuffer = await context.startRendering();

    let renderedData = renderedBuffer.getChannelData(0);

    // Initial direction is positive (1.0).

    // T=0 to T=127: playhead goes 0 up to 127.

    assert_equals(renderedData[0], 0, 'Frame 0 (positive rate)');

    assert_equals(renderedData[127], 127, 'Frame 127 (positive rate)');

    // Flip to negative (-1.0) at T=128.

    // T=128 to T=255: playhead goes 128 down to 1.

    assert_equals(renderedData[128], 128, 'Frame 128 (negative rate)');

    assert_equals(renderedData[255], 1, 'Frame 255 (negative rate)');

}, 'Dynamic direction switch positive to negative honors duration');

</script>

</body>

</html>