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/*
* Copyright (c) 2019 The WebRTC project authors. All Rights Reserved.
*
* Use of this source code is governed by a BSD-style license
* that can be found in the LICENSE file in the root of the source
* tree. An additional intellectual property rights grant can be found
* in the file PATENTS. All contributing project authors may
* be found in the AUTHORS file in the root of the source tree.
*/
#ifndef AUDIO_UTILITY_CHANNEL_MIXING_MATRIX_H_
#define AUDIO_UTILITY_CHANNEL_MIXING_MATRIX_H_
#include <vector>
#include "api/audio/channel_layout.h"
namespace webrtc {
class ChannelMixingMatrix {
public:
ChannelMixingMatrix(ChannelLayout input_layout,
int input_channels,
ChannelLayout output_layout,
int output_channels);
~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).
// The size of `matrix` is `output_channels` x `input_channels`, i.e., the
// number of rows equals the number of output channels and the number of
// columns corresponds to the number of input channels.
// This file is derived from Chromium's media/base/channel_mixing_matrix.h.
bool CreateTransformationMatrix(std::vector<std::vector<float>>* matrix);
private:
// Result transformation of input channels to output channels
std::vector<std::vector<float>>* matrix_;
// Input and output channel layout provided during construction.
const ChannelLayout input_layout_;
const int input_channels_;
const ChannelLayout output_layout_;
const 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 `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);
// Delete the copy constructor and assignment operator.
ChannelMixingMatrix(const ChannelMixingMatrix& other) = delete;
ChannelMixingMatrix& operator=(const ChannelMixingMatrix& other) = delete;
};
} // namespace webrtc
#endif // AUDIO_UTILITY_CHANNEL_MIXING_MATRIX_H_
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