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1 /* | |
2 * Copyright (c) 2017 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 #include "webrtc/modules/congestion_controller/acknowledge_bitrate_estimator.h" | |
12 | |
13 #include <cmath> | |
14 | |
15 #include "webrtc/modules/rtp_rtcp/include/rtp_rtcp_defines.h" | |
16 | |
17 namespace webrtc { | |
18 | |
19 namespace { | |
20 constexpr int kInitialRateWindowMs = 500; | |
21 constexpr int kRateWindowMs = 150; | |
22 } // namespace | |
23 | |
24 AcknowledgedBitrateEstimator::AcknowledgedBitrateEstimator() | |
25 : sum_(0), | |
26 current_win_ms_(0), | |
27 prev_time_ms_(-1), | |
28 bitrate_estimate_(-1.0f), | |
29 bitrate_estimate_var_(50.0f) {} | |
30 | |
31 void AcknowledgedBitrateEstimator::IncomingPacketFeedbackVector( | |
32 const std::vector<PacketFeedback>& packet_feedback_vector) { | |
33 RTC_DCHECK(std::is_sorted(packet_feedback_vector.begin(), | |
34 packet_feedback_vector.end(), | |
35 PacketFeedbackComparator())); | |
36 for (const auto& packet : packet_feedback_vector) | |
37 Update(packet.arrival_time_ms, packet.payload_size); | |
38 } | |
39 | |
40 void AcknowledgedBitrateEstimator::Update(int64_t now_ms, int bytes) { | |
41 int rate_window_ms = kRateWindowMs; | |
42 // We use a larger window at the beginning to get a more stable sample that | |
43 // we can use to initialize the estimate. | |
44 if (bitrate_estimate_ < 0.f) | |
45 rate_window_ms = kInitialRateWindowMs; | |
46 float bitrate_sample = UpdateWindow(now_ms, bytes, rate_window_ms); | |
47 if (bitrate_sample < 0.0f) | |
48 return; | |
49 if (bitrate_estimate_ < 0.0f) { | |
50 // This is the very first sample we get. Use it to initialize the estimate. | |
51 bitrate_estimate_ = bitrate_sample; | |
52 return; | |
53 } | |
54 // Define the sample uncertainty as a function of how far away it is from the | |
55 // current estimate. | |
56 float sample_uncertainty = | |
57 10.0f * std::abs(bitrate_estimate_ - bitrate_sample) / bitrate_estimate_; | |
58 float sample_var = sample_uncertainty * sample_uncertainty; | |
59 // Update a bayesian estimate of the rate, weighting it lower if the sample | |
60 // uncertainty is large. | |
61 // The bitrate estimate uncertainty is increased with each update to model | |
62 // that the bitrate changes over time. | |
63 float pred_bitrate_estimate_var = bitrate_estimate_var_ + 5.f; | |
64 bitrate_estimate_ = (sample_var * bitrate_estimate_ + | |
65 pred_bitrate_estimate_var * bitrate_sample) / | |
66 (sample_var + pred_bitrate_estimate_var); | |
67 bitrate_estimate_var_ = sample_var * pred_bitrate_estimate_var / | |
68 (sample_var + pred_bitrate_estimate_var); | |
69 } | |
70 | |
71 float AcknowledgedBitrateEstimator::UpdateWindow(int64_t now_ms, | |
72 int bytes, | |
73 int rate_window_ms) { | |
74 // Reset if time moves backwards. | |
75 if (now_ms < prev_time_ms_) { | |
76 prev_time_ms_ = -1; | |
77 sum_ = 0; | |
78 current_win_ms_ = 0; | |
79 } | |
80 if (prev_time_ms_ >= 0) { | |
81 current_win_ms_ += now_ms - prev_time_ms_; | |
82 // Reset if nothing has been received for more than a full window. | |
83 if (now_ms - prev_time_ms_ > rate_window_ms) { | |
84 sum_ = 0; | |
85 current_win_ms_ %= rate_window_ms; | |
86 } | |
87 } | |
88 prev_time_ms_ = now_ms; | |
89 float bitrate_sample = -1.0f; | |
90 if (current_win_ms_ >= rate_window_ms) { | |
91 bitrate_sample = 8.0f * sum_ / static_cast<float>(rate_window_ms); | |
92 current_win_ms_ -= rate_window_ms; | |
93 sum_ = 0; | |
94 } | |
95 sum_ += bytes; | |
96 return bitrate_sample; | |
97 } | |
98 | |
99 rtc::Optional<uint32_t> AcknowledgedBitrateEstimator::bitrate_bps() const { | |
100 if (bitrate_estimate_ < 0.f) | |
101 return rtc::Optional<uint32_t>(); | |
102 return rtc::Optional<uint32_t>(bitrate_estimate_ * 1000); | |
103 } | |
104 | |
105 } // namespace webrtc | |
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