1 /*
2 * Copyright (c) 2015 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
12 // Implementation of Network-Assisted Dynamic Adaptation's (NADA's) proposal.
13 // Version according to Draft Document (mentioned in references)
14 // http://tools.ietf.org/html/draft-zhu-rmcat-nada-06
15 // From March 26, 2015.
16
17 #include <math.h>
18 #include <algorithm>
19 #include <vector>
20
21 #include "webrtc/base/arraysize.h"
22 #include "webrtc/base/common.h"
23 #include "webrtc/modules/remote_bitrate_estimator/test/estimators/nada.h"
24 #include "webrtc/modules/remote_bitrate_estimator/test/bwe_test_logging.h"
25 #include "webrtc/modules/rtp_rtcp/include/receive_statistics.h"
26
27 namespace webrtc {
28 namespace testing {
29 namespace bwe {
30
31 const int64_t NadaBweReceiver::kReceivingRateTimeWindowMs = 500;
32
NadaBweReceiver(int flow_id)33 NadaBweReceiver::NadaBweReceiver(int flow_id)
34 : BweReceiver(flow_id, kReceivingRateTimeWindowMs),
35 clock_(0),
36 last_feedback_ms_(0),
37 recv_stats_(ReceiveStatistics::Create(&clock_)),
38 baseline_delay_ms_(10000), // Initialized as an upper bound.
39 delay_signal_ms_(0),
40 last_congestion_signal_ms_(0),
41 last_delays_index_(0),
42 exp_smoothed_delay_ms_(-1),
43 est_queuing_delay_signal_ms_(0) {
44 }
45
~NadaBweReceiver()46 NadaBweReceiver::~NadaBweReceiver() {
47 }
48
ReceivePacket(int64_t arrival_time_ms,const MediaPacket & media_packet)49 void NadaBweReceiver::ReceivePacket(int64_t arrival_time_ms,
50 const MediaPacket& media_packet) {
51 const float kAlpha = 0.1f; // Used for exponential smoothing.
52 const int64_t kDelayLowThresholdMs = 50; // Referred as d_th.
53 const int64_t kDelayMaxThresholdMs = 400; // Referred as d_max.
54
55 clock_.AdvanceTimeMilliseconds(arrival_time_ms - clock_.TimeInMilliseconds());
56 recv_stats_->IncomingPacket(media_packet.header(),
57 media_packet.payload_size(), false);
58 // Refered as x_n.
59 int64_t delay_ms = arrival_time_ms - media_packet.sender_timestamp_ms();
60
61 // The min should be updated within the first 10 minutes.
62 if (clock_.TimeInMilliseconds() < 10 * 60 * 1000) {
63 baseline_delay_ms_ = std::min(baseline_delay_ms_, delay_ms);
64 }
65
66 delay_signal_ms_ = delay_ms - baseline_delay_ms_; // Refered as d_n.
67 const int kMedian = arraysize(last_delays_ms_);
68 last_delays_ms_[(last_delays_index_++) % kMedian] = delay_signal_ms_;
69 int size = std::min(last_delays_index_, kMedian);
70
71 int64_t median_filtered_delay_ms_ = MedianFilter(last_delays_ms_, size);
72 exp_smoothed_delay_ms_ = ExponentialSmoothingFilter(
73 median_filtered_delay_ms_, exp_smoothed_delay_ms_, kAlpha);
74
75 if (exp_smoothed_delay_ms_ < kDelayLowThresholdMs) {
76 est_queuing_delay_signal_ms_ = exp_smoothed_delay_ms_;
77 } else if (exp_smoothed_delay_ms_ < kDelayMaxThresholdMs) {
78 est_queuing_delay_signal_ms_ = static_cast<int64_t>(
79 pow((static_cast<double>(kDelayMaxThresholdMs -
80 exp_smoothed_delay_ms_)) /
81 (kDelayMaxThresholdMs - kDelayLowThresholdMs),
82 4.0) *
83 kDelayLowThresholdMs);
84 } else {
85 est_queuing_delay_signal_ms_ = 0;
86 }
87
88 // Log received packet information.
89 BweReceiver::ReceivePacket(arrival_time_ms, media_packet);
90 }
91
GetFeedback(int64_t now_ms)92 FeedbackPacket* NadaBweReceiver::GetFeedback(int64_t now_ms) {
93 const int64_t kPacketLossPenaltyMs = 1000; // Referred as d_L.
94
95 if (now_ms - last_feedback_ms_ < 100) {
96 return NULL;
97 }
98
99 float loss_fraction = RecentPacketLossRatio();
100
101 int64_t loss_signal_ms =
102 static_cast<int64_t>(loss_fraction * kPacketLossPenaltyMs + 0.5f);
103 int64_t congestion_signal_ms = est_queuing_delay_signal_ms_ + loss_signal_ms;
104
105 float derivative = 0.0f;
106 if (last_feedback_ms_ > 0) {
107 derivative = (congestion_signal_ms - last_congestion_signal_ms_) /
108 static_cast<float>(now_ms - last_feedback_ms_);
109 }
110 last_feedback_ms_ = now_ms;
111 last_congestion_signal_ms_ = congestion_signal_ms;
112
113 int64_t corrected_send_time_ms = 0L;
114
115 if (!received_packets_.empty()) {
116 PacketIdentifierNode* latest = *(received_packets_.begin());
117 corrected_send_time_ms =
118 latest->send_time_ms + now_ms - latest->arrival_time_ms;
119 }
120
121 // Sends a tuple containing latest values of <d_hat_n, d_tilde_n, x_n, x'_n,
122 // R_r> and additional information.
123 return new NadaFeedback(flow_id_, now_ms * 1000, exp_smoothed_delay_ms_,
124 est_queuing_delay_signal_ms_, congestion_signal_ms,
125 derivative, RecentKbps(), corrected_send_time_ms);
126 }
127
128 // If size is even, the median is the average of the two middlemost numbers.
MedianFilter(int64_t * last_delays_ms,int size)129 int64_t NadaBweReceiver::MedianFilter(int64_t* last_delays_ms, int size) {
130 std::vector<int64_t> array_copy(last_delays_ms, last_delays_ms + size);
131 std::nth_element(array_copy.begin(), array_copy.begin() + size / 2,
132 array_copy.end());
133 if (size % 2 == 1) {
134 // Typically, size = 5. For odd size values, right and left are equal.
135 return array_copy.at(size / 2);
136 }
137 int64_t right = array_copy.at(size / 2);
138 std::nth_element(array_copy.begin(), array_copy.begin() + (size - 1) / 2,
139 array_copy.end());
140 int64_t left = array_copy.at((size - 1) / 2);
141 return (left + right + 1) / 2;
142 }
143
ExponentialSmoothingFilter(int64_t new_value,int64_t last_smoothed_value,float alpha)144 int64_t NadaBweReceiver::ExponentialSmoothingFilter(int64_t new_value,
145 int64_t last_smoothed_value,
146 float alpha) {
147 if (last_smoothed_value < 0) {
148 return new_value; // Handling initial case.
149 }
150 return static_cast<int64_t>(alpha * new_value +
151 (1.0f - alpha) * last_smoothed_value + 0.5f);
152 }
153
154 // Implementation according to Cisco's proposal by default.
NadaBweSender(int kbps,BitrateObserver * observer,Clock * clock)155 NadaBweSender::NadaBweSender(int kbps, BitrateObserver* observer, Clock* clock)
156 : BweSender(kbps), // Referred as "Reference Rate" = R_n.,
157 clock_(clock),
158 observer_(observer),
159 original_operating_mode_(true) {
160 }
161
NadaBweSender(BitrateObserver * observer,Clock * clock)162 NadaBweSender::NadaBweSender(BitrateObserver* observer, Clock* clock)
163 : BweSender(kMinBitrateKbps), // Referred as "Reference Rate" = R_n.
164 clock_(clock),
165 observer_(observer),
166 original_operating_mode_(true) {
167 }
168
~NadaBweSender()169 NadaBweSender::~NadaBweSender() {
170 }
171
GetFeedbackIntervalMs() const172 int NadaBweSender::GetFeedbackIntervalMs() const {
173 return 100;
174 }
175
GiveFeedback(const FeedbackPacket & feedback)176 void NadaBweSender::GiveFeedback(const FeedbackPacket& feedback) {
177 const NadaFeedback& fb = static_cast<const NadaFeedback&>(feedback);
178
179 // Following parameters might be optimized.
180 const int64_t kQueuingDelayUpperBoundMs = 10;
181 const float kDerivativeUpperBound = 10.0f / min_feedback_delay_ms_;
182 // In the modified version, a higher kMinUpperBound allows a higher d_hat
183 // upper bound for calling AcceleratedRampUp.
184 const float kProportionalityDelayBits = 20.0f;
185
186 int64_t now_ms = clock_->TimeInMilliseconds();
187 float delta_s = now_ms - last_feedback_ms_;
188 last_feedback_ms_ = now_ms;
189 // Update delta_0.
190 min_feedback_delay_ms_ =
191 std::min(min_feedback_delay_ms_, static_cast<int64_t>(delta_s));
192
193 // Update RTT_0.
194 int64_t rtt_ms = now_ms - fb.latest_send_time_ms();
195 min_round_trip_time_ms_ = std::min(min_round_trip_time_ms_, rtt_ms);
196
197 // Independent limits for AcceleratedRampUp conditions variables:
198 // x_n, d_tilde and x'_n in the original implementation, plus
199 // d_hat and receiving_rate in the modified one.
200 // There should be no packet losses/marking, hence x_n == d_tilde.
201 if (original_operating_mode_) {
202 // Original if conditions and rate update.
203 if (fb.congestion_signal() == fb.est_queuing_delay_signal_ms() &&
204 fb.est_queuing_delay_signal_ms() < kQueuingDelayUpperBoundMs &&
205 fb.derivative() < kDerivativeUpperBound) {
206 AcceleratedRampUp(fb);
207 } else {
208 GradualRateUpdate(fb, delta_s, 1.0);
209 }
210 } else {
211 // Modified if conditions and rate update; new ramp down mode.
212 if (fb.congestion_signal() == fb.est_queuing_delay_signal_ms() &&
213 fb.est_queuing_delay_signal_ms() < kQueuingDelayUpperBoundMs &&
214 fb.exp_smoothed_delay_ms() <
215 kMinBitrateKbps / kProportionalityDelayBits &&
216 fb.derivative() < kDerivativeUpperBound &&
217 fb.receiving_rate() > kMinBitrateKbps) {
218 AcceleratedRampUp(fb);
219 } else if (fb.congestion_signal() > kMaxCongestionSignalMs ||
220 fb.exp_smoothed_delay_ms() > kMaxCongestionSignalMs) {
221 AcceleratedRampDown(fb);
222 } else {
223 double bitrate_reference =
224 (2.0 * bitrate_kbps_) / (kMaxBitrateKbps + kMinBitrateKbps);
225 double smoothing_factor = pow(bitrate_reference, 0.75);
226 GradualRateUpdate(fb, delta_s, smoothing_factor);
227 }
228 }
229
230 bitrate_kbps_ = std::min(bitrate_kbps_, kMaxBitrateKbps);
231 bitrate_kbps_ = std::max(bitrate_kbps_, kMinBitrateKbps);
232
233 observer_->OnNetworkChanged(1000 * bitrate_kbps_, 0, rtt_ms);
234 }
235
TimeUntilNextProcess()236 int64_t NadaBweSender::TimeUntilNextProcess() {
237 return 100;
238 }
239
Process()240 int NadaBweSender::Process() {
241 return 0;
242 }
243
AcceleratedRampUp(const NadaFeedback & fb)244 void NadaBweSender::AcceleratedRampUp(const NadaFeedback& fb) {
245 const int kMaxRampUpQueuingDelayMs = 50; // Referred as T_th.
246 const float kGamma0 = 0.5f; // Referred as gamma_0.
247
248 float gamma =
249 std::min(kGamma0, static_cast<float>(kMaxRampUpQueuingDelayMs) /
250 (min_round_trip_time_ms_ + min_feedback_delay_ms_));
251
252 bitrate_kbps_ = static_cast<int>((1.0f + gamma) * fb.receiving_rate() + 0.5f);
253 }
254
AcceleratedRampDown(const NadaFeedback & fb)255 void NadaBweSender::AcceleratedRampDown(const NadaFeedback& fb) {
256 const float kGamma0 = 0.9f;
257 float gamma = 3.0f * kMaxCongestionSignalMs /
258 (fb.congestion_signal() + fb.exp_smoothed_delay_ms());
259 gamma = std::min(gamma, kGamma0);
260 bitrate_kbps_ = gamma * fb.receiving_rate() + 0.5f;
261 }
262
GradualRateUpdate(const NadaFeedback & fb,float delta_s,double smoothing_factor)263 void NadaBweSender::GradualRateUpdate(const NadaFeedback& fb,
264 float delta_s,
265 double smoothing_factor) {
266 const float kTauOMs = 500.0f; // Referred as tau_o.
267 const float kEta = 2.0f; // Referred as eta.
268 const float kKappa = 1.0f; // Referred as kappa.
269 const float kReferenceDelayMs = 10.0f; // Referred as x_ref.
270 const float kPriorityWeight = 1.0f; // Referred as w.
271
272 float x_hat = fb.congestion_signal() + kEta * kTauOMs * fb.derivative();
273
274 float kTheta =
275 kPriorityWeight * (kMaxBitrateKbps - kMinBitrateKbps) * kReferenceDelayMs;
276
277 int original_increase =
278 static_cast<int>((kKappa * delta_s *
279 (kTheta - (bitrate_kbps_ - kMinBitrateKbps) * x_hat)) /
280 (kTauOMs * kTauOMs) +
281 0.5f);
282
283 bitrate_kbps_ = bitrate_kbps_ + smoothing_factor * original_increase;
284 }
285
286 } // namespace bwe
287 } // namespace testing
288 } // namespace webrtc
289