media/base/channel_mixing_matrix.h

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef MEDIA_BASE_CHANNEL_MIXING_MATRIX_H_
   6 #define MEDIA_BASE_CHANNEL_MIXING_MATRIX_H_
   7
   8 #include <vector>
   9
  10 #include "base/macros.h"
  11 #include "media/base/channel_layout.h"
  12 #include "media/base/media_export.h"
  13
  14 namespace media {
  15
  16 class MEDIA_EXPORT ChannelMixingMatrix {
  17  public:
  18   ChannelMixingMatrix(ChannelLayout input_layout,
  19                       int input_channels,
  20                       ChannelLayout output_layout,
  21                       int output_channels);
  22
  23   ~ChannelMixingMatrix();
  24
  25   // Create the transformation matrix of input channels to output channels.
  26   // Updates the empty matrix with the transformation, and returns true
  27   // if the transformation is just a remapping of channels (no mixing).
  28   bool CreateTransformationMatrix(std::vector<std::vector<float>>* matrix);
  29
  30  private:
  31   // Result transformation of input channels to output channels
  32   std::vector<std::vector<float>>* matrix_;
  33
  34   // Input and output channel layout provided during construction.
  35   ChannelLayout input_layout_;
  36   int input_channels_;
  37   ChannelLayout output_layout_;
  38   int output_channels_;
  39
  40   // Helper variable for tracking which inputs are currently unaccounted,
  41   // should be empty after construction completes.
  42   std::vector<Channels> unaccounted_inputs_;
  43
  44   // Helper methods for managing unaccounted input channels.
  45   void AccountFor(Channels ch);
  46   bool IsUnaccounted(Channels ch) const;
  47
  48   // Helper methods for checking if |ch| exists in either |input_layout_| or
  49   // |output_layout_| respectively.
  50   bool HasInputChannel(Channels ch) const;
  51   bool HasOutputChannel(Channels ch) const;
  52
  53   // Helper methods for updating |matrix_| with the proper value for
  54   // mixing |input_ch| into |output_ch|.  MixWithoutAccounting() does not
  55   // remove the channel from |unaccounted_inputs_|.
  56   void Mix(Channels input_ch, Channels output_ch, float scale);
  57   void MixWithoutAccounting(Channels input_ch, Channels output_ch, float scale);
  58
  59   DISALLOW_COPY_AND_ASSIGN(ChannelMixingMatrix);
  60 };
  61
  62 }  // namespace media
  63
  64 #endif  // MEDIA_BASE_CHANNEL_MIXING_MATRIX_H_