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Unified Diff: Source/platform/audio/StereoPanner.cpp

Issue 691143007: Implement StereoPannerNode for robust stereo panning (Closed) Base URL: https://chromium.googlesource.com/chromium/blink.git@master
Patch Set: Created 6 years, 1 month ago
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Index: Source/platform/audio/StereoPanner.cpp
diff --git a/Source/platform/audio/StereoPanner.cpp b/Source/platform/audio/StereoPanner.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..7eaa17253df532902aa83f6437b9dc7ca20fb5bd
--- /dev/null
+++ b/Source/platform/audio/StereoPanner.cpp
@@ -0,0 +1,159 @@
+// 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 "platform/audio/StereoPanner.h"
+
+#include "platform/audio/AudioBus.h"
+#include "platform/audio/AudioUtilities.h"
+#include "wtf/MathExtras.h"
+#include <algorithm>
+
+// Use a 50ms smoothing / de-zippering time-constant.
+const float SmoothingTimeConstant = 0.050f;
+
+namespace blink {
+
+StereoPanner::StereoPanner(float sampleRate) : Spatializer(PanningModelEqualPower)
+ , m_isFirstRender(true)
+ , m_gainL(0.5)
+ , m_gainR(0.5)
+{
+ m_smoothingConstant = AudioUtilities::discreteTimeConstantForSampleRate(SmoothingTimeConstant, sampleRate);
+}
+
+void StereoPanner::panWithSampleAccurateValues(const AudioBus* inputBus, AudioBus* outputBus, const float* panValues, size_t framesToProcess)
+{
+ bool isInputSafe = inputBus
+ && (inputBus->numberOfChannels() == 1 || inputBus->numberOfChannels() == 2)
+ && framesToProcess <= inputBus->length();
+ ASSERT(isInputSafe);
+ if (!isInputSafe)
+ return;
+
+ unsigned numberOfInputChannels = inputBus->numberOfChannels();
+
+ bool isOutputSafe = outputBus
+ && outputBus->numberOfChannels() == 2
+ && framesToProcess <= outputBus->length();
+ ASSERT(isOutputSafe);
+ if (!isOutputSafe)
+ return;
+
+ const float* sourceL = inputBus->channel(0)->data();
+ const float* sourceR = numberOfInputChannels > 1 ? inputBus->channel(1)->data() : sourceL;
+ float* destinationL = outputBus->channelByType(AudioBus::ChannelLeft)->mutableData();
+ float* destinationR = outputBus->channelByType(AudioBus::ChannelRight)->mutableData();
+
+ if (!sourceL || !sourceR || !destinationL || !destinationR)
+ return;
+
+ // Cache in local variables.
+ double gainL = m_gainL;
+ double gainR = m_gainR;
+
+ int n = framesToProcess;
+
+ if (numberOfInputChannels == 1) { // For mono source case.
+ while (n--) {
+ float inputL = *sourceL++;
+ float panValue = clampTo(*panValues++, -1.0, 1.0);
+ float panPosition = (panValue * 0.5 + 0.5) * piOverTwoDouble;
+ gainL = std::cos(panPosition);
+ gainR = std::sin(panPosition);
+ *destinationL++ = static_cast<float>(inputL * gainL);
+ *destinationR++ = static_cast<float>(inputL * gainR);
+ }
+ } else { // For stereo source case.
+ while (n--) {
+ float inputL = *sourceL++;
+ float inputR = *sourceR++;
+ float panValue = clampTo(*panValues++, -1.0, 1.0);
+ float panPosition = (panValue * 0.5 + 0.5) * piOverTwoDouble;
+ gainL = std::cos(panPosition);
+ gainR = std::sin(panPosition);
+ *destinationL++ = static_cast<float>(inputL * gainL);
+ *destinationR++ = static_cast<float>(inputR * gainR);
+ }
+ }
+
+ m_gainL = gainL;
+ m_gainR = gainR;
+}
+
+void StereoPanner::panToTargetValue(const AudioBus* inputBus, AudioBus* outputBus, float panValue, size_t framesToProcess)
+{
+ bool isInputSafe = inputBus
+ && (inputBus->numberOfChannels() == 1 || inputBus->numberOfChannels() == 2)
+ && framesToProcess <= inputBus->length();
+ ASSERT(isInputSafe);
+ if (!isInputSafe)
+ return;
+
+ unsigned numberOfInputChannels = inputBus->numberOfChannels();
+
+ bool isOutputSafe = outputBus
+ && outputBus->numberOfChannels() == 2
+ && framesToProcess <= outputBus->length();
+ ASSERT(isOutputSafe);
+ if (!isOutputSafe)
+ return;
+
+ const float* sourceL = inputBus->channel(0)->data();
+ const float* sourceR = numberOfInputChannels > 1 ? inputBus->channel(1)->data() : sourceL;
+ float* destinationL = outputBus->channelByType(AudioBus::ChannelLeft)->mutableData();
+ float* destinationR = outputBus->channelByType(AudioBus::ChannelRight)->mutableData();
+
+ if (!sourceL || !sourceR || !destinationL || !destinationR)
+ return;
+
+ float panValueClamped = clampTo(panValue, -1.0, 1.0);
+ double targetGainL = std::cos(piOverTwoDouble * (panValueClamped * 0.5 + 0.5));
+ double targetGainR = std::sin(piOverTwoDouble * (panValueClamped * 0.5 + 0.5));
+
+ // Don't de-zipper on first render call.
+ if (m_isFirstRender) {
+ m_isFirstRender = false;
+ m_gainL = targetGainL;
+ m_gainR = targetGainR;
+ }
+
+ // Cache in local variables.
+ double gainL = m_gainL;
+ double gainR = m_gainR;
+
+ // Get local copy of smoothing constant.
+ const double SmoothingConstant = m_smoothingConstant;
+
+ int n = framesToProcess;
+
+ if (numberOfInputChannels == 1) { // For mono source case.
+ while (n--) {
+ float inputL = *sourceL++;
+ gainL += (targetGainL - gainL) * SmoothingConstant;
+ gainR += (targetGainR - gainR) * SmoothingConstant;
+ *destinationL++ = static_cast<float>(inputL * gainL);
+ *destinationR++ = static_cast<float>(inputL * gainR);
+ }
+ } else { // For stereo source case.
+ while (n--) {
+ float inputL = *sourceL++;
+ float inputR = *sourceR++;
+ gainL += (targetGainL - gainL) * SmoothingConstant;
+ gainR += (targetGainR - gainR) * SmoothingConstant;
+ *destinationL++ = static_cast<float>(inputL * gainL);
+ *destinationR++ = static_cast<float>(inputR * gainR);
+ }
+ }
+
+ m_gainL = gainL;
+ m_gainR = gainR;
+}
+
+} // namespace blink
+
+#endif // ENABLE(WEB_AUDIO)
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