1 files changed, 56 insertions, 0 deletions
diff --git a/third_party/libwebrtc/rtc_tools/frame_analyzer/linear_least_squares.h b/third_party/libwebrtc/rtc_tools/frame_analyzer/linear_least_squares.h
new file mode 100644
index 0000000000..7006db1d65
--- /dev/null
+++ b/third_party/libwebrtc/rtc_tools/frame_analyzer/linear_least_squares.h
@@ -0,0 +1,56 @@
+/*
+ *  Copyright (c) 2018 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 RTC_TOOLS_FRAME_ANALYZER_LINEAR_LEAST_SQUARES_H_
+#define RTC_TOOLS_FRAME_ANALYZER_LINEAR_LEAST_SQUARES_H_
+
+#include <stdint.h>
+
+#include <valarray>
+#include <vector>
+
+#include "absl/types/optional.h"
+
+namespace webrtc {
+namespace test {
+
+// This class is used for finding a matrix b that roughly solves the equation:
+// y = x * b. This is generally impossible to do exactly, so the problem is
+// rephrased as finding the matrix b that minimizes the difference:
+// |y - x * b|^2. Calling multiple AddObservations() is equivalent to
+// concatenating the observation vectors and calling AddObservations() once. The
+// reason for doing it incrementally is that we can't store the raw YUV values
+// for a whole video file in memory at once. This class has a constant memory
+// footprint, regardless how may times AddObservations() is called.
+class IncrementalLinearLeastSquares {
+ public:
+  IncrementalLinearLeastSquares();
+  ~IncrementalLinearLeastSquares();
+
+  // Add a number of observations. The subvectors of x and y must have the same
+  // length.
+  void AddObservations(const std::vector<std::vector<uint8_t>>& x,
+                       const std::vector<std::vector<uint8_t>>& y);
+
+  // Calculate and return the best linear solution, given the observations so
+  // far.
+  std::vector<std::vector<double>> GetBestSolution() const;
+
+ private:
+  // Running sum of x^T * x.
+  absl::optional<std::valarray<std::valarray<uint64_t>>> sum_xx;
+  // Running sum of x^T * y.
+  absl::optional<std::valarray<std::valarray<uint64_t>>> sum_xy;
+};
+
+}  // namespace test
+}  // namespace webrtc
+
+#endif  // RTC_TOOLS_FRAME_ANALYZER_LINEAR_LEAST_SQUARES_H_