| /* |
| * Copyright (c) 2019 The WebRTC project authors. All Rights Reserved. |
| * |
| * Use of this source code is governed by a BSD-style license |
| * that can be found in the LICENSE file in the root of the source |
| * tree. An additional intellectual property rights grant can be found |
| * in the file PATENTS. All contributing project authors may |
| * be found in the AUTHORS file in the root of the source tree. |
| */ |
| |
| #include "video/encoder_bitrate_adjuster.h" |
| |
| #include <algorithm> |
| #include <memory> |
| #include <vector> |
| |
| #include "rtc_base/experiments/rate_control_settings.h" |
| #include "rtc_base/logging.h" |
| #include "rtc_base/time_utils.h" |
| #include "system_wrappers/include/field_trial.h" |
| |
| namespace webrtc { |
| namespace { |
| // Helper struct with metadata for a single spatial layer. |
| struct LayerRateInfo { |
| double link_utilization_factor = 0.0; |
| double media_utilization_factor = 0.0; |
| DataRate target_rate = DataRate::Zero(); |
| |
| DataRate WantedOvershoot() const { |
| // If there is headroom, allow bitrate to go up to media rate limit. |
| // Still limit media utilization to 1.0, so we don't overshoot over long |
| // runs even if we have headroom. |
| const double max_media_utilization = |
| std::max(1.0, media_utilization_factor); |
| if (link_utilization_factor > max_media_utilization) { |
| return (link_utilization_factor - max_media_utilization) * target_rate; |
| } |
| return DataRate::Zero(); |
| } |
| }; |
| } // namespace |
| constexpr int64_t EncoderBitrateAdjuster::kWindowSizeMs; |
| constexpr size_t EncoderBitrateAdjuster::kMinFramesSinceLayoutChange; |
| constexpr double EncoderBitrateAdjuster::kDefaultUtilizationFactor; |
| |
| EncoderBitrateAdjuster::EncoderBitrateAdjuster(const VideoCodec& codec_settings) |
| : utilize_bandwidth_headroom_(RateControlSettings::ParseFromFieldTrials() |
| .BitrateAdjusterCanUseNetworkHeadroom()), |
| frames_since_layout_change_(0), |
| min_bitrates_bps_{} { |
| if (codec_settings.codecType == VideoCodecType::kVideoCodecVP9) { |
| for (size_t si = 0; si < codec_settings.VP9().numberOfSpatialLayers; ++si) { |
| if (codec_settings.spatialLayers[si].active) { |
| min_bitrates_bps_[si] = |
| std::max(codec_settings.minBitrate * 1000, |
| codec_settings.spatialLayers[si].minBitrate * 1000); |
| } |
| } |
| } else { |
| for (size_t si = 0; si < codec_settings.numberOfSimulcastStreams; ++si) { |
| if (codec_settings.simulcastStream[si].active) { |
| min_bitrates_bps_[si] = |
| std::max(codec_settings.minBitrate * 1000, |
| codec_settings.simulcastStream[si].minBitrate * 1000); |
| } |
| } |
| } |
| } |
| |
| EncoderBitrateAdjuster::~EncoderBitrateAdjuster() = default; |
| |
| VideoBitrateAllocation EncoderBitrateAdjuster::AdjustRateAllocation( |
| const VideoEncoder::RateControlParameters& rates) { |
| current_rate_control_parameters_ = rates; |
| |
| // First check that overshoot detectors exist, and store per spatial layer |
| // how many active temporal layers we have. |
| size_t active_tls_[kMaxSpatialLayers] = {}; |
| for (size_t si = 0; si < kMaxSpatialLayers; ++si) { |
| active_tls_[si] = 0; |
| for (size_t ti = 0; ti < kMaxTemporalStreams; ++ti) { |
| // Layer is enabled iff it has both positive bitrate and framerate target. |
| if (rates.bitrate.GetBitrate(si, ti) > 0 && |
| current_fps_allocation_[si].size() > ti && |
| current_fps_allocation_[si][ti] > 0) { |
| ++active_tls_[si]; |
| if (!overshoot_detectors_[si][ti]) { |
| overshoot_detectors_[si][ti] = |
| std::make_unique<EncoderOvershootDetector>(kWindowSizeMs); |
| frames_since_layout_change_ = 0; |
| } |
| } else if (overshoot_detectors_[si][ti]) { |
| // Layer removed, destroy overshoot detector. |
| overshoot_detectors_[si][ti].reset(); |
| frames_since_layout_change_ = 0; |
| } |
| } |
| } |
| |
| // Next poll the overshoot detectors and populate the adjusted allocation. |
| const int64_t now_ms = rtc::TimeMillis(); |
| VideoBitrateAllocation adjusted_allocation; |
| std::vector<LayerRateInfo> layer_infos; |
| DataRate wanted_overshoot_sum = DataRate::Zero(); |
| |
| for (size_t si = 0; si < kMaxSpatialLayers; ++si) { |
| layer_infos.emplace_back(); |
| LayerRateInfo& layer_info = layer_infos.back(); |
| |
| layer_info.target_rate = |
| DataRate::bps(rates.bitrate.GetSpatialLayerSum(si)); |
| |
| // Adjustment is done per spatial layer only (not per temporal layer). |
| if (frames_since_layout_change_ < kMinFramesSinceLayoutChange) { |
| layer_info.link_utilization_factor = kDefaultUtilizationFactor; |
| layer_info.media_utilization_factor = kDefaultUtilizationFactor; |
| } else if (active_tls_[si] == 0 || |
| layer_info.target_rate == DataRate::Zero()) { |
| // No signaled temporal layers, or no bitrate set. Could either be unused |
| // spatial layer or bitrate dynamic mode; pass bitrate through without any |
| // change. |
| layer_info.link_utilization_factor = 1.0; |
| layer_info.media_utilization_factor = 1.0; |
| } else if (active_tls_[si] == 1) { |
| // A single active temporal layer, this might mean single layer or that |
| // encoder does not support temporal layers. Merge target bitrates for |
| // this spatial layer. |
| RTC_DCHECK(overshoot_detectors_[si][0]); |
| layer_info.link_utilization_factor = |
| overshoot_detectors_[si][0] |
| ->GetNetworkRateUtilizationFactor(now_ms) |
| .value_or(kDefaultUtilizationFactor); |
| layer_info.media_utilization_factor = |
| overshoot_detectors_[si][0] |
| ->GetMediaRateUtilizationFactor(now_ms) |
| .value_or(kDefaultUtilizationFactor); |
| } else if (layer_info.target_rate > DataRate::Zero()) { |
| // Multiple temporal layers enabled for this spatial layer. Update rate |
| // for each of them and make a weighted average of utilization factors, |
| // with bitrate fraction used as weight. |
| // If any layer is missing a utilization factor, fall back to default. |
| layer_info.link_utilization_factor = 0.0; |
| layer_info.media_utilization_factor = 0.0; |
| for (size_t ti = 0; ti < active_tls_[si]; ++ti) { |
| RTC_DCHECK(overshoot_detectors_[si][ti]); |
| const absl::optional<double> ti_link_utilization_factor = |
| overshoot_detectors_[si][ti]->GetNetworkRateUtilizationFactor( |
| now_ms); |
| const absl::optional<double> ti_media_utilization_factor = |
| overshoot_detectors_[si][ti]->GetMediaRateUtilizationFactor(now_ms); |
| if (!ti_link_utilization_factor || !ti_media_utilization_factor) { |
| layer_info.link_utilization_factor = kDefaultUtilizationFactor; |
| layer_info.media_utilization_factor = kDefaultUtilizationFactor; |
| break; |
| } |
| const double weight = |
| static_cast<double>(rates.bitrate.GetBitrate(si, ti)) / |
| layer_info.target_rate.bps(); |
| layer_info.link_utilization_factor += |
| weight * ti_link_utilization_factor.value(); |
| layer_info.media_utilization_factor += |
| weight * ti_media_utilization_factor.value(); |
| } |
| } else { |
| RTC_NOTREACHED(); |
| } |
| |
| if (layer_info.link_utilization_factor < 1.0) { |
| // TODO(sprang): Consider checking underuse and allowing it to cancel some |
| // potential overuse by other streams. |
| |
| // Don't boost target bitrate if encoder is under-using. |
| layer_info.link_utilization_factor = 1.0; |
| } else { |
| // Don't reduce encoder target below 50%, in which case the frame dropper |
| // should kick in instead. |
| layer_info.link_utilization_factor = |
| std::min(layer_info.link_utilization_factor, 2.0); |
| |
| // Keep track of sum of desired overshoot bitrate. |
| wanted_overshoot_sum += layer_info.WantedOvershoot(); |
| } |
| } |
| |
| // Available link headroom that can be used to fill wanted overshoot. |
| DataRate available_headroom = DataRate::Zero(); |
| if (utilize_bandwidth_headroom_) { |
| available_headroom = |
| rates.bandwidth_allocation - DataRate::bps(rates.bitrate.get_sum_bps()); |
| } |
| |
| // All wanted overshoots are satisfied in the same proportion based on |
| // available headroom. |
| const double granted_overshoot_ratio = |
| wanted_overshoot_sum == DataRate::Zero() |
| ? 0.0 |
| : std::min(1.0, available_headroom.bps<double>() / |
| wanted_overshoot_sum.bps()); |
| |
| for (size_t si = 0; si < kMaxSpatialLayers; ++si) { |
| LayerRateInfo& layer_info = layer_infos[si]; |
| double utilization_factor = layer_info.link_utilization_factor; |
| DataRate allowed_overshoot = |
| granted_overshoot_ratio * layer_info.WantedOvershoot(); |
| if (allowed_overshoot > DataRate::Zero()) { |
| // Pretend the target bitrate is higher by the allowed overshoot. |
| // Since utilization_factor = actual_bitrate / target_bitrate, it can be |
| // done by multiplying by old_target_bitrate / new_target_bitrate. |
| utilization_factor *= layer_info.target_rate.bps<double>() / |
| (allowed_overshoot.bps<double>() + |
| layer_info.target_rate.bps<double>()); |
| } |
| |
| if (min_bitrates_bps_[si] > 0 && |
| layer_info.target_rate > DataRate::Zero() && |
| DataRate::bps(min_bitrates_bps_[si]) < layer_info.target_rate) { |
| // Make sure rate adjuster doesn't push target bitrate below minimum. |
| utilization_factor = |
| std::min(utilization_factor, layer_info.target_rate.bps<double>() / |
| min_bitrates_bps_[si]); |
| } |
| |
| if (layer_info.target_rate > DataRate::Zero()) { |
| RTC_LOG(LS_VERBOSE) << "Utilization factors for spatial index " << si |
| << ": link = " << layer_info.link_utilization_factor |
| << ", media = " << layer_info.media_utilization_factor |
| << ", wanted overshoot = " |
| << layer_info.WantedOvershoot().bps() |
| << " bps, available headroom = " |
| << available_headroom.bps() |
| << " bps, total utilization factor = " |
| << utilization_factor; |
| } |
| |
| // Populate the adjusted allocation with determined utilization factor. |
| if (active_tls_[si] == 1 && |
| layer_info.target_rate > |
| DataRate::bps(rates.bitrate.GetBitrate(si, 0))) { |
| // Bitrate allocation indicates temporal layer usage, but encoder |
| // does not seem to support it. Pipe all bitrate into a single |
| // overshoot detector. |
| uint32_t adjusted_layer_bitrate_bps = |
| std::min(static_cast<uint32_t>( |
| layer_info.target_rate.bps() / utilization_factor + 0.5), |
| layer_info.target_rate.bps<uint32_t>()); |
| adjusted_allocation.SetBitrate(si, 0, adjusted_layer_bitrate_bps); |
| } else { |
| for (size_t ti = 0; ti < kMaxTemporalStreams; ++ti) { |
| if (rates.bitrate.HasBitrate(si, ti)) { |
| uint32_t adjusted_layer_bitrate_bps = std::min( |
| static_cast<uint32_t>( |
| rates.bitrate.GetBitrate(si, ti) / utilization_factor + 0.5), |
| rates.bitrate.GetBitrate(si, ti)); |
| adjusted_allocation.SetBitrate(si, ti, adjusted_layer_bitrate_bps); |
| } |
| } |
| } |
| |
| // In case of rounding errors, add bitrate to TL0 until min bitrate |
| // constraint has been met. |
| const uint32_t adjusted_spatial_layer_sum = |
| adjusted_allocation.GetSpatialLayerSum(si); |
| if (layer_info.target_rate > DataRate::Zero() && |
| adjusted_spatial_layer_sum < min_bitrates_bps_[si]) { |
| adjusted_allocation.SetBitrate(si, 0, |
| adjusted_allocation.GetBitrate(si, 0) + |
| min_bitrates_bps_[si] - |
| adjusted_spatial_layer_sum); |
| } |
| |
| // Update all detectors with the new adjusted bitrate targets. |
| for (size_t ti = 0; ti < kMaxTemporalStreams; ++ti) { |
| const uint32_t layer_bitrate_bps = adjusted_allocation.GetBitrate(si, ti); |
| // Overshoot detector may not exist, eg for ScreenshareLayers case. |
| if (layer_bitrate_bps > 0 && overshoot_detectors_[si][ti]) { |
| // Number of frames in this layer alone is not cumulative, so |
| // subtract fps from any low temporal layer. |
| const double fps_fraction = |
| static_cast<double>( |
| current_fps_allocation_[si][ti] - |
| (ti == 0 ? 0 : current_fps_allocation_[si][ti - 1])) / |
| VideoEncoder::EncoderInfo::kMaxFramerateFraction; |
| |
| overshoot_detectors_[si][ti]->SetTargetRate( |
| DataRate::bps(layer_bitrate_bps), |
| fps_fraction * rates.framerate_fps, now_ms); |
| } |
| } |
| } |
| |
| // Since no spatial layers or streams are toggled by the adjustment |
| // bw-limited flag stays the same. |
| adjusted_allocation.set_bw_limited(rates.bitrate.is_bw_limited()); |
| |
| return adjusted_allocation; |
| } |
| |
| void EncoderBitrateAdjuster::OnEncoderInfo( |
| const VideoEncoder::EncoderInfo& encoder_info) { |
| // Copy allocation into current state and re-allocate. |
| for (size_t si = 0; si < kMaxSpatialLayers; ++si) { |
| current_fps_allocation_[si] = encoder_info.fps_allocation[si]; |
| } |
| |
| // Trigger re-allocation so that overshoot detectors have correct targets. |
| AdjustRateAllocation(current_rate_control_parameters_); |
| } |
| |
| void EncoderBitrateAdjuster::OnEncodedFrame(const EncodedImage& encoded_image, |
| int temporal_index) { |
| ++frames_since_layout_change_; |
| // Detectors may not exist, for instance if ScreenshareLayers is used. |
| auto& detector = |
| overshoot_detectors_[encoded_image.SpatialIndex().value_or(0)] |
| [temporal_index]; |
| if (detector) { |
| detector->OnEncodedFrame(encoded_image.size(), rtc::TimeMillis()); |
| } |
| } |
| |
| void EncoderBitrateAdjuster::Reset() { |
| for (size_t si = 0; si < kMaxSpatialLayers; ++si) { |
| for (size_t ti = 0; ti < kMaxTemporalStreams; ++ti) { |
| overshoot_detectors_[si][ti].reset(); |
| } |
| } |
| // Call AdjustRateAllocation() with the last know bitrate allocation, so that |
| // the appropriate overuse detectors are immediately re-created. |
| AdjustRateAllocation(current_rate_control_parameters_); |
| } |
| |
| } // namespace webrtc |
