1
    2
    3
    4
    5
    6
    7
    8
    9
   10
   11
   12
   13
   14
   15
   16
   17
   18
   19
   20
   21
   22
   23
   24
   25
   26
   27
   28
   29
   30
   31
   32
   33
   34
   35
   36
   37
   38
   39
   40
   41
   42
   43
   44
   45
   46
   47
   48
   49
   50
   51
   52
   53
   54
   55
   56
   57
   58
   59
   60
   61
   62
   63
   64
   65
   66
   67
   68
   69
   70


media / base / channel_mixing_matrix.h [blame]

// Copyright 2012 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef MEDIA_BASE_CHANNEL_MIXING_MATRIX_H_
#define MEDIA_BASE_CHANNEL_MIXING_MATRIX_H_

#include <vector>

#include "base/memory/raw_ptr.h"
#include "media/base/channel_layout.h"
#include "media/base/media_export.h"

namespace media {

class MEDIA_EXPORT ChannelMixingMatrix {
 public:
  ChannelMixingMatrix(ChannelLayout input_layout,
                      int input_channels,
                      ChannelLayout output_layout,
                      int output_channels);

  ChannelMixingMatrix(const ChannelMixingMatrix&) = delete;
  ChannelMixingMatrix& operator=(const ChannelMixingMatrix&) = delete;

  ~ChannelMixingMatrix();

  // Create the transformation matrix of input channels to output channels.
  // Updates the empty matrix with the transformation, and returns true
  // if the transformation is just a remapping of channels (no mixing).
  bool CreateTransformationMatrix(std::vector<std::vector<float>>* matrix);

 private:
  // Result transformation of input channels to output channels
  raw_ptr<std::vector<std::vector<float>>> matrix_;

  // Input and output channel layout provided during construction.
  ChannelLayout input_layout_;
  int input_channels_;
  ChannelLayout output_layout_;
  int output_channels_;

  // Helper variable for tracking which inputs are currently unaccounted,
  // should be empty after construction completes.
  std::vector<Channels> unaccounted_inputs_;

  // Helper methods for managing unaccounted input channels.
  void AccountFor(Channels ch);
  bool IsUnaccounted(Channels ch) const;

  // Helper methods for checking if input or output layout is mono or 1.1 (Mono
  // + LFE).
  bool IsMonoInputLayout() const;
  bool IsMonoOutputLayout() const;

  // Helper methods for checking if |ch| exists in either |input_layout_| or
  // |output_layout_| respectively.
  bool HasInputChannel(Channels ch) const;
  bool HasOutputChannel(Channels ch) const;

  // Helper methods for updating |matrix_| with the proper value for
  // mixing |input_ch| into |output_ch|.  MixWithoutAccounting() does not
  // remove the channel from |unaccounted_inputs_|.
  void Mix(Channels input_ch, Channels output_ch, float scale);
  void MixWithoutAccounting(Channels input_ch, Channels output_ch, float scale);
};

}  // namespace media

#endif  // MEDIA_BASE_CHANNEL_MIXING_MATRIX_H_