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29 #include "ConvolverNode.h"
31 #include "AudioBuffer.h"
32 #include "AudioContext.h"
33 #include "AudioNodeInput.h"
34 #include "AudioNodeOutput.h"
36 #include <wtf/MainThread.h>
38 // Note about empirical tuning:
39 // The maximum FFT size affects reverb performance and accuracy.
40 // If the reverb is single-threaded and processes entirely in the real-time audio thread,
41 // it's important not to make this too high. In this case 8192 is a good value.
42 // But, the Reverb object is multi-threaded, so we want this as high as possible without losing too much accuracy.
43 // Very large FFTs will have worse phase errors. Given these constraints 32768 is a good compromise.
44 const size_t MaxFFTSize = 32768;
48 ConvolverNode::ConvolverNode(AudioContext* context, double sampleRate)
49 : AudioNode(context, sampleRate)
51 addInput(adoptPtr(new AudioNodeInput(this)));
52 addOutput(adoptPtr(new AudioNodeOutput(this, 2)));
54 setType(NodeTypeConvolver);
59 ConvolverNode::~ConvolverNode()
64 void ConvolverNode::process(size_t framesToProcess)
66 AudioBus* outputBus = output(0)->bus();
69 // Synchronize with possible dynamic changes to the impulse response.
70 if (m_processLock.tryLock()) {
71 if (!isInitialized() || !m_reverb.get())
74 // Process using the convolution engine.
75 // 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.
76 // 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
77 // we keep getting fed silence.
78 m_reverb->process(input(0)->bus(), outputBus, framesToProcess);
81 m_processLock.unlock();
83 // Too bad - the tryLock() failed. We must be in the middle of setting a new impulse response.
88 void ConvolverNode::reset()
90 MutexLocker locker(m_processLock);
95 void ConvolverNode::initialize()
100 AudioNode::initialize();
103 void ConvolverNode::uninitialize()
105 if (!isInitialized())
109 AudioNode::uninitialize();
112 void ConvolverNode::setBuffer(AudioBuffer* buffer)
114 ASSERT(isMainThread());
120 unsigned numberOfChannels = buffer->numberOfChannels();
121 size_t bufferLength = buffer->length();
123 // The current implementation supports up to four channel impulse responses, which are interpreted as true-stereo (see Reverb class).
124 bool isBufferGood = numberOfChannels > 0 && numberOfChannels <= 4 && bufferLength;
125 ASSERT(isBufferGood);
129 // Wrap the AudioBuffer by an AudioBus. It's an efficient pointer set and not a memcpy().
130 // This memory is simply used in the Reverb constructor and no reference to it is kept for later use in that class.
131 AudioBus bufferBus(numberOfChannels, bufferLength, false);
132 for (unsigned i = 0; i < numberOfChannels; ++i)
133 bufferBus.setChannelMemory(i, buffer->getChannelData(i)->data(), bufferLength);
135 // Create the reverb with the given impulse response.
136 bool useBackgroundThreads = !context()->isOfflineContext();
137 OwnPtr<Reverb> reverb = adoptPtr(new Reverb(&bufferBus, AudioNode::ProcessingSizeInFrames, MaxFFTSize, 2, useBackgroundThreads));
140 // Synchronize with process().
141 MutexLocker locker(m_processLock);
142 m_reverb = reverb.release();
147 AudioBuffer* ConvolverNode::buffer()
149 ASSERT(isMainThread());
150 return m_buffer.get();
153 } // namespace WebCore
155 #endif // ENABLE(WEB_AUDIO)