Implement StereoPannerNode for robust stereo panning

Source/modules/webaudio/StereoPannerNode.cpp

Index: Source/modules/webaudio/StereoPannerNode.cpp
diff --git a/Source/modules/webaudio/StereoPannerNode.cpp b/Source/modules/webaudio/StereoPannerNode.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..60e047c616330dcdf3d152a9aa190d08370873fa
--- /dev/null
+++ b/Source/modules/webaudio/StereoPannerNode.cpp
@@ -0,0 +1,165 @@
+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "config.h"
+
+#if ENABLE(WEB_AUDIO)
+
+#include "modules/webaudio/StereoPannerNode.h"
+
+#include "bindings/core/v8/ExceptionMessages.h"
+#include "bindings/core/v8/ExceptionState.h"
+#include "core/dom/ExecutionContext.h"
+#include "modules/webaudio/AudioContext.h"
+#include "modules/webaudio/AudioNodeInput.h"
+#include "modules/webaudio/AudioNodeOutput.h"
+#include "platform/audio/StereoPanner.h"
+#include "wtf/MathExtras.h"
+
+namespace blink {
+
+StereoPannerNode::StereoPannerNode(AudioContext* context, float sampleRate)
+    : AudioNode(context, sampleRate)
+    , m_sampleAccuratePanValues(AudioNode::ProcessingSizeInFrames)
+{
+    m_pan = AudioParam::create(context, 0);
+
+    addInput();
+    addOutput(AudioNodeOutput::create(this, 2));
+
+    // The node-specific default mixing rules declare that StereoPannerNode
+    // can handle mono to stereo and stereo to stereo conversion.
+    m_channelCount = 2;
+    m_channelCountMode = ClampedMax;
+    m_channelInterpretation = AudioBus::Speakers;
+
+    setNodeType(NodeTypeStereoPanner);
+
+    initialize();
+}
+
+StereoPannerNode::~StereoPannerNode()
+{
+    ASSERT(!isInitialized());
+}
+
+void StereoPannerNode::dispose()
+{
+    uninitialize();
+    AudioNode::dispose();
+}
+
+void StereoPannerNode::process(size_t framesToProcess)
+{
+    AudioBus* outputBus = output(0)->bus();
+
+    if (!isInitialized() || !input(0)->isConnected() || !m_stereoPanner.get()) {
+        outputBus->zero();
+        return;
+    }
+
+    AudioBus* inputBus = input(0)->bus();
+    if (!inputBus) {
+        outputBus->zero();
+        return;
+    }
+
+    if (pan()->hasSampleAccurateValues()) {
+        // Apply sample-accurate panning specified by AudioParam automation.
+        ASSERT(framesToProcess <= m_sampleAccuratePanValues.size());
+        if (framesToProcess <= m_sampleAccuratePanValues.size()) {
+            float* panValues = m_sampleAccuratePanValues.data();
+            pan()->calculateSampleAccurateValues(panValues, framesToProcess);
+            m_stereoPanner->panWithSampleAccurateValues(inputBus, outputBus, panValues, framesToProcess);
+        }
+    } else {
+        m_stereoPanner->panToTargetValue(inputBus, outputBus, pan()->value(), framesToProcess);
+    }
+}
+
+void StereoPannerNode::initialize()
+{
+    if (isInitialized())
+        return;
+
+    m_stereoPanner = Spatializer::create(Spatializer::PanningModelEqualPower, sampleRate());
+
+    AudioNode::initialize();
+}
+
+void StereoPannerNode::uninitialize()
+{
+    if (!isInitialized())
+        return;
+
+    m_stereoPanner.clear();
+
+    AudioNode::uninitialize();
+}
+
+void StereoPannerNode::setChannelCount(unsigned long channelCount, ExceptionState& exceptionState)
+{
+    ASSERT(isMainThread());
+    AudioContext::AutoLocker locker(context());
+
+    // A PannerNode only supports 1 or 2 channels
+    if (channelCount > 0 && channelCount <= 2) {
+        if (m_channelCount != channelCount) {
+            m_channelCount = channelCount;
+            if (m_channelCountMode != Max)
+                updateChannelsForInputs();
+        }
+    } else {
+        exceptionState.throwDOMException(
+            NotSupportedError,
+            ExceptionMessages::indexOutsideRange<unsigned long>(
+                "channelCount",
+                channelCount,
+                1,
+                ExceptionMessages::InclusiveBound,
+                2,
+                ExceptionMessages::InclusiveBound));
+    }
+}
+
+void StereoPannerNode::setChannelCountMode(const String& mode, ExceptionState& exceptionState)
+{
+    ASSERT(isMainThread());
+    AudioContext::AutoLocker locker(context());
+
+    ChannelCountMode oldMode = m_channelCountMode;
+
+    if (mode == "clamped-max") {
+        m_newChannelCountMode = ClampedMax;
+    } else if (mode == "explicit") {
+        m_newChannelCountMode = Explicit;
+    } else if (mode == "max") {
+        // This is not supported for a StereoPannerNode, which can only handle
+        // 1 or 2 channels.
+        exceptionState.throwDOMException(
+            NotSupportedError,
+            ExceptionMessages::failedToSet(
+                "channelCountMode",
+                "StereoPannerNode",
+                "'max' is not allowed"));
+        m_newChannelCountMode = oldMode;
+    } else {
+        // Do nothing for other invalid values.
+        m_newChannelCountMode = oldMode;
+    }
+
+    if (m_newChannelCountMode != oldMode)
+        context()->addChangedChannelCountMode(this);
+}
+
+void StereoPannerNode::trace(Visitor* visitor)
+{
+    visitor->trace(m_stereoPanner);
+    visitor->trace(m_pan);
+    AudioNode::trace(visitor);
+}
+
+} // namespace blink
+
+#endif // ENABLE(WEB_AUDIO)