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 #include "webrtc/modules/pacing/bitrate_prober.h"
12
13 #include <assert.h>
14 #include <algorithm>
15 #include <limits>
16 #include <sstream>
17
18 #include "webrtc/base/logging.h"
19 #include "webrtc/modules/pacing/paced_sender.h"
20
21 namespace webrtc {
22
23 namespace {
ComputeDeltaFromBitrate(size_t packet_size,int bitrate_bps)24 int ComputeDeltaFromBitrate(size_t packet_size, int bitrate_bps) {
25 assert(bitrate_bps > 0);
26 // Compute the time delta needed to send packet_size bytes at bitrate_bps
27 // bps. Result is in milliseconds.
28 return static_cast<int>(1000ll * static_cast<int64_t>(packet_size) * 8ll /
29 bitrate_bps);
30 }
31 } // namespace
32
BitrateProber()33 BitrateProber::BitrateProber()
34 : probing_state_(kDisabled),
35 packet_size_last_send_(0),
36 time_last_send_ms_(-1) {
37 }
38
SetEnabled(bool enable)39 void BitrateProber::SetEnabled(bool enable) {
40 if (enable) {
41 if (probing_state_ == kDisabled) {
42 probing_state_ = kAllowedToProbe;
43 LOG(LS_INFO) << "Initial bandwidth probing enabled";
44 }
45 } else {
46 probing_state_ = kDisabled;
47 LOG(LS_INFO) << "Initial bandwidth probing disabled";
48 }
49 }
50
IsProbing() const51 bool BitrateProber::IsProbing() const {
52 return probing_state_ == kProbing;
53 }
54
MaybeInitializeProbe(int bitrate_bps)55 void BitrateProber::MaybeInitializeProbe(int bitrate_bps) {
56 if (probing_state_ != kAllowedToProbe)
57 return;
58 probe_bitrates_.clear();
59 // Max number of packets used for probing.
60 const int kMaxNumProbes = 2;
61 const int kPacketsPerProbe = 5;
62 const float kProbeBitrateMultipliers[kMaxNumProbes] = {3, 6};
63 int bitrates_bps[kMaxNumProbes];
64 std::stringstream bitrate_log;
65 bitrate_log << "Start probing for bandwidth, bitrates:";
66 for (int i = 0; i < kMaxNumProbes; ++i) {
67 bitrates_bps[i] = kProbeBitrateMultipliers[i] * bitrate_bps;
68 bitrate_log << " " << bitrates_bps[i];
69 // We need one extra to get 5 deltas for the first probe.
70 if (i == 0)
71 probe_bitrates_.push_back(bitrates_bps[i]);
72 for (int j = 0; j < kPacketsPerProbe; ++j)
73 probe_bitrates_.push_back(bitrates_bps[i]);
74 }
75 bitrate_log << ", num packets: " << probe_bitrates_.size();
76 LOG(LS_INFO) << bitrate_log.str().c_str();
77 probing_state_ = kProbing;
78 }
79
TimeUntilNextProbe(int64_t now_ms)80 int BitrateProber::TimeUntilNextProbe(int64_t now_ms) {
81 if (probing_state_ != kDisabled && probe_bitrates_.empty()) {
82 probing_state_ = kWait;
83 }
84 if (probe_bitrates_.empty()) {
85 // No probe started, or waiting for next probe.
86 return -1;
87 }
88 int64_t elapsed_time_ms = now_ms - time_last_send_ms_;
89 // We will send the first probe packet immediately if no packet has been
90 // sent before.
91 int time_until_probe_ms = 0;
92 if (packet_size_last_send_ > PacedSender::kMinProbePacketSize &&
93 probing_state_ == kProbing) {
94 int next_delta_ms = ComputeDeltaFromBitrate(packet_size_last_send_,
95 probe_bitrates_.front());
96 time_until_probe_ms = next_delta_ms - elapsed_time_ms;
97 // There is no point in trying to probe with less than 1 ms between packets
98 // as it essentially means trying to probe at infinite bandwidth.
99 const int kMinProbeDeltaMs = 1;
100 // If we have waited more than 3 ms for a new packet to probe with we will
101 // consider this probing session over.
102 const int kMaxProbeDelayMs = 3;
103 if (next_delta_ms < kMinProbeDeltaMs ||
104 time_until_probe_ms < -kMaxProbeDelayMs) {
105 // We currently disable probing after the first probe, as we only want
106 // to probe at the beginning of a connection. We should set this to
107 // kWait if we later want to probe periodically.
108 probing_state_ = kWait;
109 LOG(LS_INFO) << "Next delta too small, stop probing.";
110 time_until_probe_ms = 0;
111 }
112 }
113 return std::max(time_until_probe_ms, 0);
114 }
115
RecommendedPacketSize() const116 size_t BitrateProber::RecommendedPacketSize() const {
117 return packet_size_last_send_;
118 }
119
PacketSent(int64_t now_ms,size_t packet_size)120 void BitrateProber::PacketSent(int64_t now_ms, size_t packet_size) {
121 assert(packet_size > 0);
122 packet_size_last_send_ = packet_size;
123 time_last_send_ms_ = now_ms;
124 if (probing_state_ != kProbing)
125 return;
126 if (!probe_bitrates_.empty())
127 probe_bitrates_.pop_front();
128 }
129 } // namespace webrtc
130