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..dbaac71e6c1045296a6ffeadc7f1d3f8d05cf7ed
--- /dev/null
+++ b/Source/modules/webaudio/StereoPannerNode.cpp
@@ -0,0 +1,134 @@
+// Copyright 2014 The Chromium Authors. All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//    * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//    * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//    * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#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, 0.0);

[Raymond Toy, 2014/11/11 19:41:47]

No trailing ".0" on floating point constants unless required:
http://dev.chromium.org/blink/coding-style#TOC-Floating-point-literals

[hongchan, 2014/11/12 00:06:54]

Done.

+
+    addInput();
+    addOutput(AudioNodeOutput::create(this, 2));
+
+    // This node-specific default mixing rules declare that StereoPannerNode
+    // can handles mono to stereo and stereo to stereo conversion.

[Raymond Toy, 2014/11/11 19:41:47]

Typo: "handles" -> "handle"

[hongchan, 2014/11/12 00:06:53]

Done.

[hongchan, 2014/11/12 00:06:54]

Done.

+    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::trace(Visitor* visitor)
+{
+    visitor->trace(m_stereoPanner);
+    visitor->trace(m_pan);
+    AudioNode::trace(visitor);
+}
+
+} // namespace blink
+
+#endif // ENABLE(WEB_AUDIO)