chromium/src/third_party/blink/renderer/platform/audio/up_sampler.h

/*
 * Copyright (C) 2013 Google Inc. All rights reserved.
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#ifndef THIRD_PARTY_BLINK_RENDERER_PLATFORM_AUDIO_UP_SAMPLER_H_
#define THIRD_PARTY_BLINK_RENDERER_PLATFORM_AUDIO_UP_SAMPLER_H_

#include <memory>

#include "base/macros.h"
#include "third_party/blink/renderer/platform/audio/audio_array.h"
#include "third_party/blink/renderer/platform/audio/direct_convolver.h"
#include "third_party/blink/renderer/platform/audio/simple_fft_convolver.h"
#include "third_party/blink/renderer/platform/wtf/allocator/allocator.h"

namespace blink {

// UpSampler up-samples the source stream by a factor of 2x.

class PLATFORM_EXPORT UpSampler {
  USING_FAST_MALLOC(UpSampler);

 public:
  explicit UpSampler(size_t input_block_size);

  // The destination buffer |destP| is of size sourceFramesToProcess * 2.
  void Process(const float* source_p,
               float* dest_p,
               size_t source_frames_to_process);

  void Reset();

  // Latency based on the source sample-rate.
  size_t LatencyFrames() const;

 private:
  enum { kDefaultKernelSize = 128 };

  size_t input_block_size_;

  // Computes the odd sample-frames of the output.
  std::unique_ptr<DirectConvolver> direct_convolver_;
  std::unique_ptr<SimpleFFTConvolver> simple_fft_convolver_;

  AudioFloatArray temp_buffer_;

  // Delay line for generating the even sample-frames of the output.
  // The source samples are delayed exactly to match the linear phase delay of
  // the FIR filter (convolution) used to generate the odd sample-frames of the
  // output.
  AudioFloatArray input_buffer_;

  DISALLOW_COPY_AND_ASSIGN(UpSampler);
};

}  // namespace blink

#endif  // THIRD_PARTY_BLINK_RENDERER_PLATFORM_AUDIO_UP_SAMPLER_H_