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29 #include "modules/webaudio/ConvolverNode.h"
31 #include "bindings/v8/ExceptionState.h"
32 #include "core/dom/ExceptionCode.h"
33 #include "platform/audio/Reverb.h"
34 #include "modules/webaudio/AudioBuffer.h"
35 #include "modules/webaudio/AudioContext.h"
36 #include "modules/webaudio/AudioNodeInput.h"
37 #include "modules/webaudio/AudioNodeOutput.h"
38 #include "wtf/MainThread.h"
40 // Note about empirical tuning:
41 // The maximum FFT size affects reverb performance and accuracy.
42 // If the reverb is single-threaded and processes entirely in the real-time audio thread,
43 // it's important not to make this too high. In this case 8192 is a good value.
44 // But, the Reverb object is multi-threaded, so we want this as high as possible without losing too much accuracy.
45 // Very large FFTs will have worse phase errors. Given these constraints 32768 is a good compromise.
46 const size_t MaxFFTSize = 32768;
50 ConvolverNode::ConvolverNode(AudioContext* context, float sampleRate)
51 : AudioNode(context, sampleRate)
54 ScriptWrappable::init(this);
55 addInput(adoptPtr(new AudioNodeInput(this)));
56 addOutput(adoptPtr(new AudioNodeOutput(this, 2)));
58 // Node-specific default mixing rules.
60 m_channelCountMode = ClampedMax;
61 m_channelInterpretation = AudioBus::Speakers;
63 setNodeType(NodeTypeConvolver);
67 ConvolverNode::~ConvolverNode()
72 void ConvolverNode::process(size_t framesToProcess)
74 AudioBus* outputBus = output(0)->bus();
77 // Synchronize with possible dynamic changes to the impulse response.
78 MutexTryLocker tryLocker(m_processLock);
79 if (tryLocker.locked()) {
80 if (!isInitialized() || !m_reverb.get())
83 // Process using the convolution engine.
84 // Note that we can handle the case where nothing is connected to the input, in which case we'll just feed silence into the convolver.
85 // FIXME: If we wanted to get fancy we could try to factor in the 'tail time' and stop processing once the tail dies down if
86 // we keep getting fed silence.
87 m_reverb->process(input(0)->bus(), outputBus, framesToProcess);
90 // Too bad - the tryLock() failed. We must be in the middle of setting a new impulse response.
95 void ConvolverNode::initialize()
100 AudioNode::initialize();
103 void ConvolverNode::uninitialize()
105 if (!isInitialized())
109 AudioNode::uninitialize();
112 void ConvolverNode::setBuffer(AudioBuffer* buffer, ExceptionState& exceptionState)
114 ASSERT(isMainThread());
119 if (buffer->sampleRate() != context()->sampleRate()) {
120 exceptionState.throwDOMException(
122 "The buffer sample rate of " + String::number(buffer->sampleRate())
123 + " does not match the context rate of " + String::number(context()->sampleRate())
127 unsigned numberOfChannels = buffer->numberOfChannels();
128 size_t bufferLength = buffer->length();
130 // The current implementation supports up to four channel impulse responses, which are interpreted as true-stereo (see Reverb class).
131 bool isBufferGood = numberOfChannels > 0 && numberOfChannels <= 4 && bufferLength;
132 ASSERT(isBufferGood);
136 // Wrap the AudioBuffer by an AudioBus. It's an efficient pointer set and not a memcpy().
137 // This memory is simply used in the Reverb constructor and no reference to it is kept for later use in that class.
138 RefPtr<AudioBus> bufferBus = AudioBus::create(numberOfChannels, bufferLength, false);
139 for (unsigned i = 0; i < numberOfChannels; ++i)
140 bufferBus->setChannelMemory(i, buffer->getChannelData(i)->data(), bufferLength);
142 bufferBus->setSampleRate(buffer->sampleRate());
144 // Create the reverb with the given impulse response.
145 bool useBackgroundThreads = !context()->isOfflineContext();
146 OwnPtr<Reverb> reverb = adoptPtr(new Reverb(bufferBus.get(), AudioNode::ProcessingSizeInFrames, MaxFFTSize, 2, useBackgroundThreads, m_normalize));
149 // Synchronize with process().
150 MutexLocker locker(m_processLock);
151 m_reverb = reverb.release();
156 AudioBuffer* ConvolverNode::buffer()
158 ASSERT(isMainThread());
159 return m_buffer.get();
162 double ConvolverNode::tailTime() const
164 MutexTryLocker tryLocker(m_processLock);
165 if (tryLocker.locked())
166 return m_reverb ? m_reverb->impulseResponseLength() / static_cast<double>(sampleRate()) : 0;
167 // Since we don't want to block the Audio Device thread, we return a large value
168 // instead of trying to acquire the lock.
169 return std::numeric_limits<double>::infinity();
172 double ConvolverNode::latencyTime() const
174 MutexTryLocker tryLocker(m_processLock);
175 if (tryLocker.locked())
176 return m_reverb ? m_reverb->latencyFrames() / static_cast<double>(sampleRate()) : 0;
177 // Since we don't want to block the Audio Device thread, we return a large value
178 // instead of trying to acquire the lock.
179 return std::numeric_limits<double>::infinity();
182 void ConvolverNode::trace(Visitor* visitor)
184 visitor->trace(m_buffer);
185 AudioNode::trace(visitor);
188 } // namespace WebCore
190 #endif // ENABLE(WEB_AUDIO)