1/*
2 *  Copyright (c) 2014 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 WEBRTC_MODULES_REMOTE_BITRATE_ESTIMATOR_AIMD_RATE_CONTROL_H_
12#define WEBRTC_MODULES_REMOTE_BITRATE_ESTIMATOR_AIMD_RATE_CONTROL_H_
13
14#include "webrtc/base/constructormagic.h"
15#include "webrtc/modules/remote_bitrate_estimator/include/bwe_defines.h"
16
17namespace webrtc {
18
19// A rate control implementation based on additive increases of
20// bitrate when no over-use is detected and multiplicative decreases when
21// over-uses are detected. When we think the available bandwidth has changes or
22// is unknown, we will switch to a "slow-start mode" where we increase
23// multiplicatively.
24class AimdRateControl {
25 public:
26  AimdRateControl();
27  virtual ~AimdRateControl() {}
28
29  // Returns true if there is a valid estimate of the incoming bitrate, false
30  // otherwise.
31  bool ValidEstimate() const;
32  void SetMinBitrate(int min_bitrate_bps);
33  int64_t GetFeedbackInterval() const;
34  // Returns true if the bitrate estimate hasn't been changed for more than
35  // an RTT, or if the incoming_bitrate is more than 5% above the current
36  // estimate. Should be used to decide if we should reduce the rate further
37  // when over-using.
38  bool TimeToReduceFurther(int64_t time_now,
39                           uint32_t incoming_bitrate_bps) const;
40  uint32_t LatestEstimate() const;
41  uint32_t UpdateBandwidthEstimate(int64_t now_ms);
42  void SetRtt(int64_t rtt);
43  void Update(const RateControlInput* input, int64_t now_ms);
44  void SetEstimate(int bitrate_bps, int64_t now_ms);
45
46 private:
47  // Update the target bitrate according based on, among other things,
48  // the current rate control state, the current target bitrate and the incoming
49  // bitrate. When in the "increase" state the bitrate will be increased either
50  // additively or multiplicatively depending on the rate control region. When
51  // in the "decrease" state the bitrate will be decreased to slightly below the
52  // incoming bitrate. When in the "hold" state the bitrate will be kept
53  // constant to allow built up queues to drain.
54  uint32_t ChangeBitrate(uint32_t current_bit_rate,
55                         uint32_t incoming_bit_rate,
56                         int64_t now_ms);
57  uint32_t MultiplicativeRateIncrease(int64_t now_ms, int64_t last_ms,
58                                      uint32_t current_bitrate_bps) const;
59  uint32_t AdditiveRateIncrease(int64_t now_ms, int64_t last_ms,
60                                int64_t response_time_ms) const;
61  void UpdateChangePeriod(int64_t now_ms);
62  void UpdateMaxBitRateEstimate(float incoming_bit_rate_kbps);
63  void ChangeState(const RateControlInput& input, int64_t now_ms);
64  void ChangeState(RateControlState new_state);
65  void ChangeRegion(RateControlRegion region);
66
67  uint32_t min_configured_bitrate_bps_;
68  uint32_t max_configured_bitrate_bps_;
69  uint32_t current_bitrate_bps_;
70  uint32_t max_hold_rate_bps_;
71  float avg_max_bitrate_kbps_;
72  float var_max_bitrate_kbps_;
73  RateControlState rate_control_state_;
74  RateControlRegion rate_control_region_;
75  int64_t time_last_bitrate_change_;
76  RateControlInput current_input_;
77  bool updated_;
78  int64_t time_first_incoming_estimate_;
79  bool bitrate_is_initialized_;
80  float beta_;
81  int64_t rtt_;
82  int64_t time_of_last_log_;
83  bool in_experiment_;
84};
85}  // namespace webrtc
86
87#endif  // WEBRTC_MODULES_REMOTE_BITRATE_ESTIMATOR_AIMD_RATE_CONTROL_H_
88