AudioBufferSourceNode.start with duration fails sometimes

cdumez · cdumez · commit 703601b447f8 · 2023-01-23T13:15:17.000-08:00
https://bugs.webkit.org/show_bug.cgi?id=248658 rdar://103178030 Reviewed by Eric Carlson and Jer Noble. Per the specification [1], if you call AudioBufferNode.start() with a `when` value that is less than the AudioContext's currentTime, it should start immediately. Previously, we were missing this logic, causing the AudioBufferNode to not start if the `when` value was in the past. [1] https://webaudio.github.io/web-audio-api/#dom-audiobuffersourcenode-start-when-offset-duration-when * LayoutTests/webaudio/audiobuffersource-start-when-in-past-expected.txt: Added. * LayoutTests/webaudio/audiobuffersource-start-when-in-past.html: Added. * Source/WebCore/Modules/webaudio/AudioBufferSourceNode.cpp: (WebCore::AudioBufferSourceNode::startPlaying): Canonical link: https://commits.webkit.org/259234@main
diff --git a/LayoutTests/webaudio/audiobuffersource-start-when-in-past-expected.txt b/LayoutTests/webaudio/audiobuffersource-start-when-in-past-expected.txt
@@ -0,0 +1,11 @@
+Tests AudioBufferSourceNode starts immediately if the `when` value passed to start() is in the past.
+
+On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE".
+
+
+PASS First half of the rendered data is identical to the source buffer
+PASS Second half of the rendered data is identical to the source buffer as well
+PASS successfullyParsed is true
+
+TEST COMPLETE
+
diff --git a/LayoutTests/webaudio/audiobuffersource-start-when-in-past.html b/LayoutTests/webaudio/audiobuffersource-start-when-in-past.html
@@ -0,0 +1,78 @@
+<!DOCTYPE html>
+<html>
+<head>
+<script src="resources/audio-testing.js"></script>
+<script src="resources/audiobuffersource-testing-legacy.js"></script>
+<script src="../resources/js-test.js"></script>
+</head>
+<body>
+<script>
+description("Tests AudioBufferSourceNode starts immediately if the `when` value passed to start() is in the past.");
+jsTestIsAsync = true;
+
+const numberOfFrames = 256;
+const sourceBufferSize = numberOfFrames / 2;
+const sampleRate = 44100.;
+
+let context = new OfflineAudioContext(1, numberOfFrames, sampleRate);
+let source = null;
+
+function createSourceNode()
+{
+    if (source) {
+        source.disconnect();
+        source.stop();
+    }
+    source = context.createBufferSource();
+    source.buffer = createTestBuffer(context, numberOfFrames / 2);
+    source.loop = true;
+    source.connect(context.destination);
+    source.start(0, 0, sourceBufferSize / sampleRate);
+}
+
+function convertToRegularJSArray(data, offset, count)
+{
+    let array = new Array();
+    let outputIndex = 0;
+    for (let i = offset; i < offset + count; ++i)
+        array[outputIndex++] = data[i];
+    return array;
+}
+
+context.suspend(sourceBufferSize / sampleRate).then(() => {
+    createSourceNode();
+    context.resume();
+});
+createSourceNode();
+context.startRendering().then((renderBuffer) => {
+    let renderedData = renderBuffer.getChannelData(0);
+    let expectedData = source.buffer.getChannelData(0);
+    let success = true;
+    for (var i = 0; i < expectedData.length; ++i) {
+        if (expectedData[i] != renderedData[i]) {
+            var s = "First half: expected: " + convertToRegularJSArray(expectedData, 0, sourceBufferSize) + " actual: " + convertToRegularJSArray(renderedData, 0, sourceBufferSize);
+            testFailed(s);
+            success = false;
+            break;
+        }
+    }
+    if (success)
+        testPassed("First half of the rendered data is identical to the source buffer");
+    
+    success = true;
+    for (var i = 0; i < expectedData.length; ++i) {
+        if (expectedData[i] != renderedData[sourceBufferSize + i]) {
+            var s = "Second half: expected: " + convertToRegularJSArray(expectedData, 0, sourceBufferSize) + " actual: " + convertToRegularJSArray(renderedData, sourceBufferSize, sourceBufferSize);
+            testFailed(s);
+            success = false;
+            break;
+        }
+    }
+    if (success)
+        testPassed("Second half of the rendered data is identical to the source buffer as well");
+
+    finishJSTest();
+});
+</script>
+</body>
+</html>
diff --git a/Source/WebCore/Modules/webaudio/AudioBufferSourceNode.cpp b/Source/WebCore/Modules/webaudio/AudioBufferSourceNode.cpp
@@ -505,7 +505,10 @@ ExceptionOr<void> AudioBufferSourceNode::startPlaying(double when, double grainO
     m_grainOffset = grainOffset;
     m_grainDuration = grainDuration.value_or(0);
     m_wasGrainDurationGiven = !!grainDuration;
-    m_startTime = when;
+
+    // If 0 is passed in for |when| or if the value is less than currentTime, then the sound will start playing immediately.
+    // https://webaudio.github.io/web-audio-api/#dom-audiobuffersourcenode-start-when-offset-duration-when
+    m_startTime = std::max(when, context().currentTime());
 
     adjustGrainParameters();
 
