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      1 /*
      2  * Copyright (C) 2011 Google Inc. All rights reserved.
      3  *
      4  * Redistribution and use in source and binary forms, with or without
      5  * modification, are permitted provided that the following conditions
      6  * are met:
      7  *
      8  * 1.  Redistributions of source code must retain the above copyright
      9  *     notice, this list of conditions and the following disclaimer.
     10  * 2.  Redistributions in binary form must reproduce the above copyright
     11  *     notice, this list of conditions and the following disclaimer in the
     12  *     documentation and/or other materials provided with the distribution.
     13  * 3.  Neither the name of Apple Computer, Inc. ("Apple") nor the names of
     14  *     its contributors may be used to endorse or promote products derived
     15  *     from this software without specific prior written permission.
     16  *
     17  * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
     18  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
     19  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
     20  * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
     21  * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
     22  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
     23  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
     24  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     25  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
     26  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     27  */
     28 
     29 #include "config.h"
     30 
     31 #if ENABLE(WEB_AUDIO)
     32 
     33 #include "core/platform/audio/MultiChannelResampler.h"
     34 
     35 #include "core/platform/audio/AudioBus.h"
     36 
     37 namespace WebCore {
     38 
     39 namespace {
     40 
     41 // ChannelProvider provides a single channel of audio data (one channel at a time) for each channel
     42 // of data provided to us in a multi-channel provider.
     43 
     44 class ChannelProvider : public AudioSourceProvider {
     45 public:
     46     ChannelProvider(AudioSourceProvider* multiChannelProvider, unsigned numberOfChannels)
     47         : m_multiChannelProvider(multiChannelProvider)
     48         , m_numberOfChannels(numberOfChannels)
     49         , m_currentChannel(0)
     50         , m_framesToProcess(0)
     51     {
     52     }
     53 
     54     // provideInput() will be called once for each channel, starting with the first channel.
     55     // Each time it's called, it will provide the next channel of data.
     56     virtual void provideInput(AudioBus* bus, size_t framesToProcess)
     57     {
     58         bool isBusGood = bus && bus->numberOfChannels() == 1;
     59         ASSERT(isBusGood);
     60         if (!isBusGood)
     61             return;
     62 
     63         // Get the data from the multi-channel provider when the first channel asks for it.
     64         // For subsequent channels, we can just dish out the channel data from that (stored in m_multiChannelBus).
     65         if (!m_currentChannel) {
     66             m_framesToProcess = framesToProcess;
     67             m_multiChannelBus = AudioBus::create(m_numberOfChannels, framesToProcess);
     68             m_multiChannelProvider->provideInput(m_multiChannelBus.get(), framesToProcess);
     69         }
     70 
     71         // All channels must ask for the same amount. This should always be the case, but let's just make sure.
     72         bool isGood = m_multiChannelBus.get() && framesToProcess == m_framesToProcess;
     73         ASSERT(isGood);
     74         if (!isGood)
     75             return;
     76 
     77         // Copy the channel data from what we received from m_multiChannelProvider.
     78         ASSERT(m_currentChannel <= m_numberOfChannels);
     79         if (m_currentChannel < m_numberOfChannels) {
     80             memcpy(bus->channel(0)->mutableData(), m_multiChannelBus->channel(m_currentChannel)->data(), sizeof(float) * framesToProcess);
     81             ++m_currentChannel;
     82         }
     83     }
     84 
     85 private:
     86     AudioSourceProvider* m_multiChannelProvider;
     87     RefPtr<AudioBus> m_multiChannelBus;
     88     unsigned m_numberOfChannels;
     89     unsigned m_currentChannel;
     90     size_t m_framesToProcess; // Used to verify that all channels ask for the same amount.
     91 };
     92 
     93 } // namespace
     94 
     95 MultiChannelResampler::MultiChannelResampler(double scaleFactor, unsigned numberOfChannels)
     96     : m_numberOfChannels(numberOfChannels)
     97 {
     98     // Create each channel's resampler.
     99     for (unsigned channelIndex = 0; channelIndex < numberOfChannels; ++channelIndex)
    100         m_kernels.append(adoptPtr(new SincResampler(scaleFactor)));
    101 }
    102 
    103 void MultiChannelResampler::process(AudioSourceProvider* provider, AudioBus* destination, size_t framesToProcess)
    104 {
    105     // The provider can provide us with multi-channel audio data. But each of our single-channel resamplers (kernels)
    106     // below requires a provider which provides a single unique channel of data.
    107     // channelProvider wraps the original multi-channel provider and dishes out one channel at a time.
    108     ChannelProvider channelProvider(provider, m_numberOfChannels);
    109 
    110     for (unsigned channelIndex = 0; channelIndex < m_numberOfChannels; ++channelIndex) {
    111         // Depending on the sample-rate scale factor, and the internal buffering used in a SincResampler
    112         // kernel, this call to process() will only sometimes call provideInput() on the channelProvider.
    113         // However, if it calls provideInput() for the first channel, then it will call it for the remaining
    114         // channels, since they all buffer in the same way and are processing the same number of frames.
    115         m_kernels[channelIndex]->process(&channelProvider,
    116                                          destination->channel(channelIndex)->mutableData(),
    117                                          framesToProcess);
    118     }
    119 }
    120 
    121 } // namespace WebCore
    122 
    123 #endif // ENABLE(WEB_AUDIO)
    124