1 /* 2 * Copyright (c) 2018 The WebRTC project authors. All Rights Reserved. 3 * 4 * Use of this source code is governed by a BSD-style license 5 * that can be found in the LICENSE file in the root of the source 6 * tree. An additional intellectual property rights grant can be found 7 * in the file PATENTS. All contributing project authors may 8 * be found in the AUTHORS file in the root of the source tree. 9 */ 10 11 #ifndef RTC_TOOLS_FRAME_ANALYZER_LINEAR_LEAST_SQUARES_H_ 12 #define RTC_TOOLS_FRAME_ANALYZER_LINEAR_LEAST_SQUARES_H_ 13 14 #include <stdint.h> 15 16 #include <valarray> 17 #include <vector> 18 19 #include "absl/types/optional.h" 20 21 namespace webrtc { 22 namespace test { 23 24 // This class is used for finding a matrix b that roughly solves the equation: 25 // y = x * b. This is generally impossible to do exactly, so the problem is 26 // rephrased as finding the matrix b that minimizes the difference: 27 // |y - x * b|^2. Calling multiple AddObservations() is equivalent to 28 // concatenating the observation vectors and calling AddObservations() once. The 29 // reason for doing it incrementally is that we can't store the raw YUV values 30 // for a whole video file in memory at once. This class has a constant memory 31 // footprint, regardless how may times AddObservations() is called. 32 class IncrementalLinearLeastSquares { 33 public: 34 IncrementalLinearLeastSquares(); 35 ~IncrementalLinearLeastSquares(); 36 37 // Add a number of observations. The subvectors of x and y must have the same 38 // length. 39 void AddObservations(const std::vector<std::vector<uint8_t>>& x, 40 const std::vector<std::vector<uint8_t>>& y); 41 42 // Calculate and return the best linear solution, given the observations so 43 // far. 44 std::vector<std::vector<double>> GetBestSolution() const; 45 46 private: 47 // Running sum of x^T * x. 48 absl::optional<std::valarray<std::valarray<uint64_t>>> sum_xx; 49 // Running sum of x^T * y. 50 absl::optional<std::valarray<std::valarray<uint64_t>>> sum_xy; 51 }; 52 53 } // namespace test 54 } // namespace webrtc 55 56 #endif // RTC_TOOLS_FRAME_ANALYZER_LINEAR_LEAST_SQUARES_H_ 57