57 lines
2.0 KiB
C++
57 lines
2.0 KiB
C++
/*
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* Copyright (c) 2018 The WebRTC project authors. All Rights Reserved.
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*
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* Use of this source code is governed by a BSD-style license
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* that can be found in the LICENSE file in the root of the source
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* tree. An additional intellectual property rights grant can be found
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* in the file PATENTS. All contributing project authors may
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* be found in the AUTHORS file in the root of the source tree.
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*/
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#ifndef RTC_TOOLS_FRAME_ANALYZER_LINEAR_LEAST_SQUARES_H_
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#define RTC_TOOLS_FRAME_ANALYZER_LINEAR_LEAST_SQUARES_H_
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#include <stdint.h>
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#include <valarray>
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#include <vector>
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#include "absl/types/optional.h"
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namespace webrtc {
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namespace test {
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// This class is used for finding a matrix b that roughly solves the equation:
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// y = x * b. This is generally impossible to do exactly, so the problem is
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// rephrased as finding the matrix b that minimizes the difference:
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// |y - x * b|^2. Calling multiple AddObservations() is equivalent to
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// concatenating the observation vectors and calling AddObservations() once. The
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// reason for doing it incrementally is that we can't store the raw YUV values
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// for a whole video file in memory at once. This class has a constant memory
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// footprint, regardless how may times AddObservations() is called.
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class IncrementalLinearLeastSquares {
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public:
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IncrementalLinearLeastSquares();
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~IncrementalLinearLeastSquares();
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// Add a number of observations. The subvectors of x and y must have the same
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// length.
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void AddObservations(const std::vector<std::vector<uint8_t>>& x,
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const std::vector<std::vector<uint8_t>>& y);
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// Calculate and return the best linear solution, given the observations so
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// far.
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std::vector<std::vector<double>> GetBestSolution() const;
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private:
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// Running sum of x^T * x.
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absl::optional<std::valarray<std::valarray<uint64_t>>> sum_xx;
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// Running sum of x^T * y.
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absl::optional<std::valarray<std::valarray<uint64_t>>> sum_xy;
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};
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} // namespace test
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} // namespace webrtc
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#endif // RTC_TOOLS_FRAME_ANALYZER_LINEAR_LEAST_SQUARES_H_
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