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Mahesh Bharadwaj Kannanchromium-wpt-export-bot
Mahesh Bharadwaj Kannan
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[WebAudio] Fix AudioBufferSourceNode start duration loop underflow
The end_frame calculation in AudioBufferSourceHandler::RenderFromBuffer was incorrectly using the duration argument from start() to constrain the physical read boundary of the audio buffer even when looping was enabled. This caused the loop calculation (virtual_delta_frames) to underflow and evaluate to a negative number, failing internal sanity checks and causing the audio node to immediately output silence. This CL fixes the issue by allowing the read boundary (end_frame) to extend to the full buffer length when looping, and relying on buffer_played_frames_ to act as the duration stopwatch instead. Bug: 40910590 Change-Id: I8ac1efd0e5ca97c9287a3bc876e5827e0ac6b698 Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/7850471 Reviewed-by: Michael Wilson <mjwilson@chromium.org> Commit-Queue: Mahesh Kannan <kmaheshb@google.com> Cr-Commit-Position: refs/heads/main@{#1632602}
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‎webaudio/the-audio-api/the-audiobuffersourcenode-interface/audiobuffersource-loop-short-duration.html‎

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<!DOCTYPE html>
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<html>
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<head>
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<title>
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audiobuffersource-loop-short-duration.html
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</title>
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<script src="/resources/testharness.js"></script>
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<script src="/resources/testharnessreport.js"></script>
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</head>
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<body>
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<script id="layout-test-code">
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promise_test(async () => {
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let sampleRate = 48000;
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let context = new OfflineAudioContext(1, 128, sampleRate);
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let buffer = context.createBuffer(1, 10, sampleRate);
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let data = buffer.getChannelData(0);
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for (let i = 0; i < 10; ++i) {
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data[i] = 1.0;
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}
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let source = context.createBufferSource();
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source.buffer = buffer;
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source.loop = true;
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// loopStart > duration
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source.loopStart = 5 / sampleRate;
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source.loopEnd = 8 / sampleRate;
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source.connect(context.destination);
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// Play only 2 frames (duration = 2/sampleRate)
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source.start(0, 0, 2 / sampleRate);
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let renderedBuffer = await context.startRendering();
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let renderedData = renderedBuffer.getChannelData(0);
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let expected = new Float32Array(128);
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expected[0] = 1.0;
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expected[1] = 1.0;
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assert_array_equals(
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renderedData,
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expected,
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'Rendered data should be exactly 2 frames of 1.0 followed by silence'
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);
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}, 'audiobuffersource-loop-short-duration');
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</script>
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</body>
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</html>

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