third_party/WebKit/Source/platform/audio/UpSampler.h

   1 /*
   2  * Copyright (C) 2013 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 are
   6  * met:
   7  *
   8  *     * Redistributions of source code must retain the above copyright
   9  * notice, this list of conditions and the following disclaimer.
  10  *     * Redistributions in binary form must reproduce the above
  11  * copyright notice, this list of conditions and the following disclaimer
  12  * in the documentation and/or other materials provided with the
  13  * distribution.
  14  *     * Neither the name of Google Inc. nor the names of its
  15  * contributors may be used to endorse or promote products derived from
  16  * this software without specific prior written permission.
  17  *
  18  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  19  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  20  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  21  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  22  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  23  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  24  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  25  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  26  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  27  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  28  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  29  */
  30
  31 #ifndef UpSampler_h
  32 #define UpSampler_h
  33
  34 #include "platform/audio/AudioArray.h"
  35 #include "platform/audio/DirectConvolver.h"
  36
  37 namespace blink {
  38
  39 // UpSampler up-samples the source stream by a factor of 2x.
  40
  41 class PLATFORM_EXPORT UpSampler {
  42 public:
  43     UpSampler(size_t inputBlockSize);
  44
  45     // The destination buffer |destP| is of size sourceFramesToProcess * 2.
  46     void process(const float* sourceP, float* destP, size_t sourceFramesToProcess);
  47
  48     void reset();
  49
  50     // Latency based on the source sample-rate.
  51     size_t latencyFrames() const;
  52
  53 private:
  54     enum { DefaultKernelSize = 128 };
  55
  56     size_t m_inputBlockSize;
  57
  58     // Computes ideal band-limited filter coefficients to sample in between each source sample-frame.
  59     // This filter will be used to compute the odd sample-frames of the output.
  60     void initializeKernel();
  61     AudioFloatArray m_kernel;
  62
  63     // Computes the odd sample-frames of the output.
  64     DirectConvolver m_convolver;
  65
  66     AudioFloatArray m_tempBuffer;
  67
  68     // Delay line for generating the even sample-frames of the output.
  69     // The source samples are delayed exactly to match the linear phase delay of the FIR filter (convolution)
  70     // used to generate the odd sample-frames of the output.
  71     AudioFloatArray m_inputBuffer;
  72 };
  73
  74 } // namespace blink
  75
  76 #endif // UpSampler_h