modules/video_coding/rtt_filter.h

/*
 *  Copyright (c) 2011 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 WEBRTC_MODULES_VIDEO_CODING_RTT_FILTER_H_
#define WEBRTC_MODULES_VIDEO_CODING_RTT_FILTER_H_

#include "webrtc/typedefs.h"

namespace webrtc {

class VCMRttFilter {
 public:
  VCMRttFilter();

  VCMRttFilter& operator=(const VCMRttFilter& rhs);

  // Resets the filter.
  void Reset();
  // Updates the filter with a new sample.
  void Update(int64_t rttMs);
  // A getter function for the current RTT level in ms.
  int64_t RttMs() const;

 private:
  // The size of the drift and jump memory buffers
  // and thus also the detection threshold for these
  // detectors in number of samples.
  enum { kMaxDriftJumpCount = 5 };
  // Detects RTT jumps by comparing the difference between
  // samples and average to the standard deviation.
  // Returns true if the long time statistics should be updated
  // and false otherwise
  bool JumpDetection(int64_t rttMs);
  // Detects RTT drifts by comparing the difference between
  // max and average to the standard deviation.
  // Returns true if the long time statistics should be updated
  // and false otherwise
  bool DriftDetection(int64_t rttMs);
  // Computes the short time average and maximum of the vector buf.
  void ShortRttFilter(int64_t* buf, uint32_t length);

  bool _gotNonZeroUpdate;
  double _avgRtt;
  double _varRtt;
  int64_t _maxRtt;
  uint32_t _filtFactCount;
  const uint32_t _filtFactMax;
  const double _jumpStdDevs;
  const double _driftStdDevs;
  int32_t _jumpCount;
  int32_t _driftCount;
  const int32_t _detectThreshold;
  int64_t _jumpBuf[kMaxDriftJumpCount];
  int64_t _driftBuf[kMaxDriftJumpCount];
};

}  // namespace webrtc

#endif  // WEBRTC_MODULES_VIDEO_CODING_RTT_FILTER_H_