third_party/WebKit/Source/platform/audio/MultiChannelResampler.cpp

   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 "platform/audio/MultiChannelResampler.h"
  34
  35 #include "platform/audio/AudioBus.h"
  36
  37 namespace blink {
  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 final : 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     void provideInput(AudioBus* bus, size_t framesToProcess) override
  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 blink
 122
 123 #endif // ENABLE(WEB_AUDIO)