Erik Språng | 7ca375c | 2019-02-06 16:20:17 +0100 | [diff] [blame] | 1 | /* |
| 2 | * Copyright (c) 2019 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 "video/encoder_overshoot_detector.h" |
| 12 | |
| 13 | #include <algorithm> |
| 14 | |
| 15 | namespace webrtc { |
Erik Språng | 6c072ef | 2019-04-01 12:57:28 +0200 | [diff] [blame] | 16 | namespace { |
| 17 | // The buffer level for media-rate utilization is allowed to go below zero, |
| 18 | // down to |
| 19 | // -(|kMaxMediaUnderrunFrames| / |target_framerate_fps_|) * |target_bitrate_|. |
| 20 | static constexpr double kMaxMediaUnderrunFrames = 5.0; |
| 21 | } // namespace |
Erik Språng | 7ca375c | 2019-02-06 16:20:17 +0100 | [diff] [blame] | 22 | |
| 23 | EncoderOvershootDetector::EncoderOvershootDetector(int64_t window_size_ms) |
| 24 | : window_size_ms_(window_size_ms), |
| 25 | time_last_update_ms_(-1), |
Erik Språng | 6c072ef | 2019-04-01 12:57:28 +0200 | [diff] [blame] | 26 | sum_network_utilization_factors_(0.0), |
| 27 | sum_media_utilization_factors_(0.0), |
Erik Språng | 7ca375c | 2019-02-06 16:20:17 +0100 | [diff] [blame] | 28 | target_bitrate_(DataRate::Zero()), |
| 29 | target_framerate_fps_(0), |
Erik Språng | 6c072ef | 2019-04-01 12:57:28 +0200 | [diff] [blame] | 30 | network_buffer_level_bits_(0), |
| 31 | media_buffer_level_bits_(0) {} |
Erik Språng | 7ca375c | 2019-02-06 16:20:17 +0100 | [diff] [blame] | 32 | |
| 33 | EncoderOvershootDetector::~EncoderOvershootDetector() = default; |
| 34 | |
| 35 | void EncoderOvershootDetector::SetTargetRate(DataRate target_bitrate, |
| 36 | double target_framerate_fps, |
| 37 | int64_t time_ms) { |
| 38 | // First leak bits according to the previous target rate. |
| 39 | if (target_bitrate_ != DataRate::Zero()) { |
| 40 | LeakBits(time_ms); |
| 41 | } else if (target_bitrate != DataRate::Zero()) { |
| 42 | // Stream was just enabled, reset state. |
| 43 | time_last_update_ms_ = time_ms; |
| 44 | utilization_factors_.clear(); |
Erik Språng | 6c072ef | 2019-04-01 12:57:28 +0200 | [diff] [blame] | 45 | sum_network_utilization_factors_ = 0.0; |
| 46 | sum_media_utilization_factors_ = 0.0; |
| 47 | network_buffer_level_bits_ = 0; |
| 48 | media_buffer_level_bits_ = 0; |
Erik Språng | 7ca375c | 2019-02-06 16:20:17 +0100 | [diff] [blame] | 49 | } |
| 50 | |
| 51 | target_bitrate_ = target_bitrate; |
| 52 | target_framerate_fps_ = target_framerate_fps; |
| 53 | } |
| 54 | |
| 55 | void EncoderOvershootDetector::OnEncodedFrame(size_t bytes, int64_t time_ms) { |
| 56 | // Leak bits from the virtual pacer buffer, according to the current target |
| 57 | // bitrate. |
| 58 | LeakBits(time_ms); |
| 59 | |
| 60 | // Ideal size of a frame given the current rates. |
Erik Språng | 6c072ef | 2019-04-01 12:57:28 +0200 | [diff] [blame] | 61 | const int64_t ideal_frame_size_bits = IdealFrameSizeBits(); |
| 62 | if (ideal_frame_size_bits == 0) { |
Erik Språng | 7ca375c | 2019-02-06 16:20:17 +0100 | [diff] [blame] | 63 | // Frame without updated bitrate and/or framerate, ignore it. |
| 64 | return; |
| 65 | } |
| 66 | |
Erik Språng | 6c072ef | 2019-04-01 12:57:28 +0200 | [diff] [blame] | 67 | const double network_utilization_factor = HandleEncodedFrame( |
| 68 | bytes * 8, ideal_frame_size_bits, time_ms, &network_buffer_level_bits_); |
| 69 | const double media_utilization_factor = HandleEncodedFrame( |
| 70 | bytes * 8, ideal_frame_size_bits, time_ms, &media_buffer_level_bits_); |
| 71 | |
| 72 | sum_network_utilization_factors_ += network_utilization_factor; |
| 73 | sum_media_utilization_factors_ += media_utilization_factor; |
| 74 | |
| 75 | utilization_factors_.emplace_back(network_utilization_factor, |
| 76 | media_utilization_factor, time_ms); |
| 77 | } |
| 78 | |
| 79 | double EncoderOvershootDetector::HandleEncodedFrame( |
| 80 | size_t frame_size_bits, |
| 81 | int64_t ideal_frame_size_bits, |
| 82 | int64_t time_ms, |
| 83 | int64_t* buffer_level_bits) const { |
Erik Språng | 7ca375c | 2019-02-06 16:20:17 +0100 | [diff] [blame] | 84 | // Add new frame to the buffer level. If doing so exceeds the ideal buffer |
| 85 | // size, penalize this frame but cap overshoot to current buffer level rather |
| 86 | // than size of this frame. This is done so that a single large frame is not |
| 87 | // penalized if the encoder afterwards compensates by dropping frames and/or |
| 88 | // reducing frame size. If however a large frame is followed by more data, |
| 89 | // we cannot pace that next frame out within one frame space. |
Erik Språng | 6c072ef | 2019-04-01 12:57:28 +0200 | [diff] [blame] | 90 | const int64_t bitsum = frame_size_bits + *buffer_level_bits; |
Erik Språng | 7ca375c | 2019-02-06 16:20:17 +0100 | [diff] [blame] | 91 | int64_t overshoot_bits = 0; |
Erik Språng | 6c072ef | 2019-04-01 12:57:28 +0200 | [diff] [blame] | 92 | if (bitsum > ideal_frame_size_bits) { |
| 93 | overshoot_bits = |
| 94 | std::min(*buffer_level_bits, bitsum - ideal_frame_size_bits); |
Erik Språng | 7ca375c | 2019-02-06 16:20:17 +0100 | [diff] [blame] | 95 | } |
| 96 | |
| 97 | // Add entry for the (over) utilization for this frame. Factor is capped |
| 98 | // at 1.0 so that we don't risk overshooting on sudden changes. |
Erik Språng | 6c072ef | 2019-04-01 12:57:28 +0200 | [diff] [blame] | 99 | double utilization_factor; |
Erik Språng | 7ca375c | 2019-02-06 16:20:17 +0100 | [diff] [blame] | 100 | if (utilization_factors_.empty()) { |
| 101 | // First frame, cannot estimate overshoot based on previous one so |
| 102 | // for this particular frame, just like as size vs optimal size. |
Erik Språng | 6c072ef | 2019-04-01 12:57:28 +0200 | [diff] [blame] | 103 | utilization_factor = std::max( |
| 104 | 1.0, static_cast<double>(frame_size_bits) / ideal_frame_size_bits); |
Erik Språng | 7ca375c | 2019-02-06 16:20:17 +0100 | [diff] [blame] | 105 | } else { |
Erik Språng | 6c072ef | 2019-04-01 12:57:28 +0200 | [diff] [blame] | 106 | utilization_factor = |
| 107 | 1.0 + (static_cast<double>(overshoot_bits) / ideal_frame_size_bits); |
Erik Språng | 7ca375c | 2019-02-06 16:20:17 +0100 | [diff] [blame] | 108 | } |
Erik Språng | 7ca375c | 2019-02-06 16:20:17 +0100 | [diff] [blame] | 109 | |
| 110 | // Remove the overshot bits from the virtual buffer so we don't penalize |
| 111 | // those bits multiple times. |
Erik Språng | 6c072ef | 2019-04-01 12:57:28 +0200 | [diff] [blame] | 112 | *buffer_level_bits -= overshoot_bits; |
| 113 | *buffer_level_bits += frame_size_bits; |
| 114 | |
| 115 | return utilization_factor; |
Erik Språng | 7ca375c | 2019-02-06 16:20:17 +0100 | [diff] [blame] | 116 | } |
| 117 | |
Erik Språng | 6c072ef | 2019-04-01 12:57:28 +0200 | [diff] [blame] | 118 | absl::optional<double> |
| 119 | EncoderOvershootDetector::GetNetworkRateUtilizationFactor(int64_t time_ms) { |
| 120 | CullOldUpdates(time_ms); |
Erik Språng | 7ca375c | 2019-02-06 16:20:17 +0100 | [diff] [blame] | 121 | |
| 122 | // No data points within window, return. |
| 123 | if (utilization_factors_.empty()) { |
| 124 | return absl::nullopt; |
| 125 | } |
| 126 | |
| 127 | // TODO(sprang): Consider changing from arithmetic mean to some other |
| 128 | // function such as 90th percentile. |
Erik Språng | 6c072ef | 2019-04-01 12:57:28 +0200 | [diff] [blame] | 129 | return sum_network_utilization_factors_ / utilization_factors_.size(); |
| 130 | } |
| 131 | |
| 132 | absl::optional<double> EncoderOvershootDetector::GetMediaRateUtilizationFactor( |
| 133 | int64_t time_ms) { |
| 134 | CullOldUpdates(time_ms); |
| 135 | |
| 136 | // No data points within window, return. |
| 137 | if (utilization_factors_.empty()) { |
| 138 | return absl::nullopt; |
| 139 | } |
| 140 | |
| 141 | return sum_media_utilization_factors_ / utilization_factors_.size(); |
Erik Språng | 7ca375c | 2019-02-06 16:20:17 +0100 | [diff] [blame] | 142 | } |
| 143 | |
| 144 | void EncoderOvershootDetector::Reset() { |
| 145 | time_last_update_ms_ = -1; |
| 146 | utilization_factors_.clear(); |
| 147 | target_bitrate_ = DataRate::Zero(); |
Erik Språng | 6c072ef | 2019-04-01 12:57:28 +0200 | [diff] [blame] | 148 | sum_network_utilization_factors_ = 0.0; |
| 149 | sum_media_utilization_factors_ = 0.0; |
Erik Språng | 7ca375c | 2019-02-06 16:20:17 +0100 | [diff] [blame] | 150 | target_framerate_fps_ = 0.0; |
Erik Språng | 6c072ef | 2019-04-01 12:57:28 +0200 | [diff] [blame] | 151 | network_buffer_level_bits_ = 0; |
| 152 | media_buffer_level_bits_ = 0; |
Erik Språng | 7ca375c | 2019-02-06 16:20:17 +0100 | [diff] [blame] | 153 | } |
| 154 | |
| 155 | int64_t EncoderOvershootDetector::IdealFrameSizeBits() const { |
| 156 | if (target_framerate_fps_ <= 0 || target_bitrate_ == DataRate::Zero()) { |
| 157 | return 0; |
| 158 | } |
| 159 | |
| 160 | // Current ideal frame size, based on the current target bitrate. |
| 161 | return static_cast<int64_t>( |
| 162 | (target_bitrate_.bps() + target_framerate_fps_ / 2) / |
| 163 | target_framerate_fps_); |
| 164 | } |
| 165 | |
| 166 | void EncoderOvershootDetector::LeakBits(int64_t time_ms) { |
| 167 | if (time_last_update_ms_ != -1 && target_bitrate_ > DataRate::Zero()) { |
| 168 | int64_t time_delta_ms = time_ms - time_last_update_ms_; |
| 169 | // Leak bits according to the current target bitrate. |
Erik Språng | 6c072ef | 2019-04-01 12:57:28 +0200 | [diff] [blame] | 170 | const int64_t leaked_bits = (target_bitrate_.bps() * time_delta_ms) / 1000; |
| 171 | |
| 172 | // Network buffer may not go below zero. |
| 173 | network_buffer_level_bits_ = |
| 174 | std::max<int64_t>(0, network_buffer_level_bits_ - leaked_bits); |
| 175 | |
| 176 | // Media buffer my go down to minus |kMaxMediaUnderrunFrames| frames worth |
| 177 | // of data. |
| 178 | const double max_underrun_seconds = |
| 179 | std::min(kMaxMediaUnderrunFrames, target_framerate_fps_) / |
| 180 | target_framerate_fps_; |
| 181 | media_buffer_level_bits_ = std::max<int64_t>( |
| 182 | -max_underrun_seconds * target_bitrate_.bps<int64_t>(), |
| 183 | media_buffer_level_bits_ - leaked_bits); |
Erik Språng | 7ca375c | 2019-02-06 16:20:17 +0100 | [diff] [blame] | 184 | } |
| 185 | time_last_update_ms_ = time_ms; |
| 186 | } |
| 187 | |
Erik Språng | 6c072ef | 2019-04-01 12:57:28 +0200 | [diff] [blame] | 188 | void EncoderOvershootDetector::CullOldUpdates(int64_t time_ms) { |
| 189 | // Cull old data points. |
| 190 | const int64_t cutoff_time_ms = time_ms - window_size_ms_; |
| 191 | while (!utilization_factors_.empty() && |
| 192 | utilization_factors_.front().update_time_ms < cutoff_time_ms) { |
| 193 | // Make sure sum is never allowed to become negative due rounding errors. |
| 194 | sum_network_utilization_factors_ = std::max( |
| 195 | 0.0, sum_network_utilization_factors_ - |
| 196 | utilization_factors_.front().network_utilization_factor); |
| 197 | sum_media_utilization_factors_ = std::max( |
| 198 | 0.0, sum_media_utilization_factors_ - |
| 199 | utilization_factors_.front().media_utilization_factor); |
| 200 | utilization_factors_.pop_front(); |
| 201 | } |
| 202 | } |
| 203 | |
Erik Språng | 7ca375c | 2019-02-06 16:20:17 +0100 | [diff] [blame] | 204 | } // namespace webrtc |