video/encoder_bitrate_adjuster.cc - src.git - Git at Google

 /*
  *  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 "absl/memory/memory.h"
 #include "rtc_base/logging.h"
 #include "rtc_base/time_utils.h"

 namespace webrtc {

 constexpr int64_t EncoderBitrateAdjuster::kWindowSizeMs;
 constexpr size_t EncoderBitrateAdjuster::kMinFramesSinceLayoutChange;
 constexpr double EncoderBitrateAdjuster::kDefaultUtilizationFactor;

 EncoderBitrateAdjuster::EncoderBitrateAdjuster(const VideoCodec& codec_settings)
     : current_total_framerate_fps_(0),
       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 VideoBitrateAllocation& bitrate_allocation,
     int framerate_fps) {
   current_bitrate_allocation_ = bitrate_allocation;
   current_total_framerate_fps_ = framerate_fps;

   // 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 (bitrate_allocation.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] =
               absl::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;
   for (size_t si = 0; si < kMaxSpatialLayers; ++si) {
     const uint32_t spatial_layer_bitrate_bps =
         bitrate_allocation.GetSpatialLayerSum(si);

     // Adjustment is done per spatial layer only (not per temporal layer).
     double utilization_factor;
     if (frames_since_layout_change_ < kMinFramesSinceLayoutChange) {
       utilization_factor = kDefaultUtilizationFactor;
     } else if (active_tls_[si] == 0 || spatial_layer_bitrate_bps == 0) {
       // No signaled temporal layers, or no bitrate set. Could either be unused
       // spatial layer or bitrate dynamic mode; pass bitrate through without any
       // change.
       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]);
       utilization_factor =
           overshoot_detectors_[si][0]->GetUtilizationFactor(now_ms).value_or(
               kDefaultUtilizationFactor);
     } else if (spatial_layer_bitrate_bps > 0) {
       // 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.
       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_utilization_factor =
             overshoot_detectors_[si][ti]->GetUtilizationFactor(now_ms);
         if (!ti_utilization_factor) {
           utilization_factor = kDefaultUtilizationFactor;
           break;
         }
         const double weight =
             static_cast<double>(bitrate_allocation.GetBitrate(si, ti)) /
             spatial_layer_bitrate_bps;
         utilization_factor += weight * ti_utilization_factor.value();
       }
     } else {
       RTC_NOTREACHED();
     }

     // Don't boost target bitrate if encoder is under-using.
     utilization_factor = std::max(utilization_factor, 1.0);

     // Don't reduce encoder target below 50%, in which case the frame dropper
     // should kick in instead.
     utilization_factor = std::min(utilization_factor, 2.0);

     if (min_bitrates_bps_[si] > 0 && spatial_layer_bitrate_bps > 0 &&
         min_bitrates_bps_[si] < spatial_layer_bitrate_bps) {
       // Make sure rate adjuster doesn't push target bitrate below minimum.
       utilization_factor = std::min(
           utilization_factor, static_cast<double>(spatial_layer_bitrate_bps) /
                                   min_bitrates_bps_[si]);
     }

     // Populate the adjusted allocation with determined utilization factor.
     if (active_tls_[si] == 1 &&
         spatial_layer_bitrate_bps > bitrate_allocation.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 = static_cast<uint32_t>(
           spatial_layer_bitrate_bps / utilization_factor + 0.5);
       adjusted_allocation.SetBitrate(si, 0, adjusted_layer_bitrate_bps);
     } else {
       for (size_t ti = 0; ti < kMaxTemporalStreams; ++ti) {
         if (bitrate_allocation.HasBitrate(si, ti)) {
           uint32_t adjusted_layer_bitrate_bps = static_cast<uint32_t>(
               bitrate_allocation.GetBitrate(si, ti) / utilization_factor + 0.5);
           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 (spatial_layer_bitrate_bps > 0 &&
         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 * current_total_framerate_fps_, now_ms);
       }
     }
   }

   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_bitrate_allocation_,
                        current_total_framerate_fps_);
 }

 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_bitrate_allocation_,
                        current_total_framerate_fps_);
 }

 }  // namespace webrtc
	/*
	* 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 "absl/memory/memory.h"
	#include "rtc_base/logging.h"
	#include "rtc_base/time_utils.h"

	namespace webrtc {

	constexpr int64_t EncoderBitrateAdjuster::kWindowSizeMs;
	constexpr size_t EncoderBitrateAdjuster::kMinFramesSinceLayoutChange;
	constexpr double EncoderBitrateAdjuster::kDefaultUtilizationFactor;

	EncoderBitrateAdjuster::EncoderBitrateAdjuster(const VideoCodec& codec_settings)
	: current_total_framerate_fps_(0),
	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 VideoBitrateAllocation& bitrate_allocation,
	int framerate_fps) {
	current_bitrate_allocation_ = bitrate_allocation;
	current_total_framerate_fps_ = framerate_fps;

	// 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 (bitrate_allocation.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] =
	absl::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;
	for (size_t si = 0; si < kMaxSpatialLayers; ++si) {
	const uint32_t spatial_layer_bitrate_bps =
	bitrate_allocation.GetSpatialLayerSum(si);

	// Adjustment is done per spatial layer only (not per temporal layer).
	double utilization_factor;
	if (frames_since_layout_change_ < kMinFramesSinceLayoutChange) {
	utilization_factor = kDefaultUtilizationFactor;
	} else if (active_tls_[si] == 0 \|\| spatial_layer_bitrate_bps == 0) {
	// No signaled temporal layers, or no bitrate set. Could either be unused
	// spatial layer or bitrate dynamic mode; pass bitrate through without any
	// change.
	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]);
	utilization_factor =
	overshoot_detectors_[si][0]->GetUtilizationFactor(now_ms).value_or(
	kDefaultUtilizationFactor);
	} else if (spatial_layer_bitrate_bps > 0) {
	// 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.
	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_utilization_factor =
	overshoot_detectors_[si][ti]->GetUtilizationFactor(now_ms);
	if (!ti_utilization_factor) {
	utilization_factor = kDefaultUtilizationFactor;
	break;
	}
	const double weight =
	static_cast<double>(bitrate_allocation.GetBitrate(si, ti)) /
	spatial_layer_bitrate_bps;
	utilization_factor += weight * ti_utilization_factor.value();
	}
	} else {
	RTC_NOTREACHED();
	}

	// Don't boost target bitrate if encoder is under-using.
	utilization_factor = std::max(utilization_factor, 1.0);

	// Don't reduce encoder target below 50%, in which case the frame dropper
	// should kick in instead.
	utilization_factor = std::min(utilization_factor, 2.0);

	if (min_bitrates_bps_[si] > 0 && spatial_layer_bitrate_bps > 0 &&
	min_bitrates_bps_[si] < spatial_layer_bitrate_bps) {
	// Make sure rate adjuster doesn't push target bitrate below minimum.
	utilization_factor = std::min(
	utilization_factor, static_cast<double>(spatial_layer_bitrate_bps) /
	min_bitrates_bps_[si]);
	}

	// Populate the adjusted allocation with determined utilization factor.
	if (active_tls_[si] == 1 &&
	spatial_layer_bitrate_bps > bitrate_allocation.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 = static_cast<uint32_t>(
	spatial_layer_bitrate_bps / utilization_factor + 0.5);
	adjusted_allocation.SetBitrate(si, 0, adjusted_layer_bitrate_bps);
	} else {
	for (size_t ti = 0; ti < kMaxTemporalStreams; ++ti) {
	if (bitrate_allocation.HasBitrate(si, ti)) {
	uint32_t adjusted_layer_bitrate_bps = static_cast<uint32_t>(
	bitrate_allocation.GetBitrate(si, ti) / utilization_factor + 0.5);
	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 (spatial_layer_bitrate_bps > 0 &&
	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 * current_total_framerate_fps_, now_ms);
	}
	}
	}

	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_bitrate_allocation_,
	current_total_framerate_fps_);
	}

	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_bitrate_allocation_,
	current_total_framerate_fps_);
	}

	} // namespace webrtc