call/adaptation/video_stream_adapter.cc - src - Git at Google

 /*
  *  Copyright 2020 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 "call/adaptation/video_stream_adapter.h"

 #include <algorithm>
 #include <limits>
 #include <utility>

 #include "absl/types/optional.h"
 #include "api/video/video_adaptation_reason.h"
 #include "api/video_codecs/video_encoder.h"
 #include "rtc_base/constructor_magic.h"
 #include "rtc_base/logging.h"
 #include "rtc_base/numerics/safe_conversions.h"

 namespace webrtc {

 const int kMinFrameRateFps = 2;

 namespace {

 // Generate suggested higher and lower frame rates and resolutions, to be
 // applied to the VideoSourceRestrictor. These are used in "maintain-resolution"
 // and "maintain-framerate". The "balanced" degradation preference also makes
 // use of BalancedDegradationPreference when generating suggestions. The
 // VideoSourceRestrictor decidedes whether or not a proposed adaptation is
 // valid.

 // For frame rate, the steps we take are 2/3 (down) and 3/2 (up).
 int GetLowerFrameRateThan(int fps) {
   RTC_DCHECK(fps != std::numeric_limits<int>::max());
   return (fps * 2) / 3;
 }
 // TODO(hbos): Use absl::optional<> instead?
 int GetHigherFrameRateThan(int fps) {
   return fps != std::numeric_limits<int>::max()
              ? (fps * 3) / 2
              : std::numeric_limits<int>::max();
 }

 // For resolution, the steps we take are 3/5 (down) and 5/3 (up).
 // Notice the asymmetry of which restriction property is set depending on if
 // we are adapting up or down:
 // - VideoSourceRestrictor::DecreaseResolution() sets the max_pixels_per_frame()
 //   to the desired target and target_pixels_per_frame() to null.
 // - VideoSourceRestrictor::IncreaseResolutionTo() sets the
 //   target_pixels_per_frame() to the desired target, and max_pixels_per_frame()
 //   is set according to VideoSourceRestrictor::GetIncreasedMaxPixelsWanted().
 int GetLowerResolutionThan(int pixel_count) {
   RTC_DCHECK(pixel_count != std::numeric_limits<int>::max());
   return (pixel_count * 3) / 5;
 }

 }  // namespace

 VideoSourceRestrictions FilterRestrictionsByDegradationPreference(
     VideoSourceRestrictions source_restrictions,
     DegradationPreference degradation_preference) {
   switch (degradation_preference) {
     case DegradationPreference::BALANCED:
       break;
     case DegradationPreference::MAINTAIN_FRAMERATE:
       source_restrictions.set_max_frame_rate(absl::nullopt);
       break;
     case DegradationPreference::MAINTAIN_RESOLUTION:
       source_restrictions.set_max_pixels_per_frame(absl::nullopt);
       source_restrictions.set_target_pixels_per_frame(absl::nullopt);
       break;
     case DegradationPreference::DISABLED:
       source_restrictions.set_max_pixels_per_frame(absl::nullopt);
       source_restrictions.set_target_pixels_per_frame(absl::nullopt);
       source_restrictions.set_max_frame_rate(absl::nullopt);
   }
   return source_restrictions;
 }

 VideoAdaptationCounters FilterVideoAdaptationCountersByDegradationPreference(
     VideoAdaptationCounters counters,
     DegradationPreference degradation_preference) {
   switch (degradation_preference) {
     case DegradationPreference::BALANCED:
       break;
     case DegradationPreference::MAINTAIN_FRAMERATE:
       counters.fps_adaptations = 0;
       break;
     case DegradationPreference::MAINTAIN_RESOLUTION:
       counters.resolution_adaptations = 0;
       break;
     case DegradationPreference::DISABLED:
       counters.resolution_adaptations = 0;
       counters.fps_adaptations = 0;
       break;
     default:
       RTC_NOTREACHED();
   }
   return counters;
 }

 // TODO(hbos): Use absl::optional<> instead?
 int GetHigherResolutionThan(int pixel_count) {
   return pixel_count != std::numeric_limits<int>::max()
              ? (pixel_count * 5) / 3
              : std::numeric_limits<int>::max();
 }

 Adaptation::Step::Step(StepType type, int target)
     : type(type), target(target) {}

 Adaptation::Adaptation(int validation_id, Step step)
     : validation_id_(validation_id),
       status_(Status::kValid),
       step_(std::move(step)),
       min_pixel_limit_reached_(false) {}

 Adaptation::Adaptation(int validation_id,
                        Step step,
                        bool min_pixel_limit_reached)
     : validation_id_(validation_id),
       status_(Status::kValid),
       step_(std::move(step)),
       min_pixel_limit_reached_(min_pixel_limit_reached) {}

 Adaptation::Adaptation(int validation_id, Status invalid_status)
     : validation_id_(validation_id),
       status_(invalid_status),
       step_(absl::nullopt),
       min_pixel_limit_reached_(false) {
   RTC_DCHECK_NE(status_, Status::kValid);
 }

 Adaptation::Adaptation(int validation_id,
                        Status invalid_status,
                        bool min_pixel_limit_reached)
     : validation_id_(validation_id),
       status_(invalid_status),
       step_(absl::nullopt),
       min_pixel_limit_reached_(min_pixel_limit_reached) {
   RTC_DCHECK_NE(status_, Status::kValid);
 }

 Adaptation::Status Adaptation::status() const {
   return status_;
 }

 bool Adaptation::min_pixel_limit_reached() const {
   return min_pixel_limit_reached_;
 }

 const Adaptation::Step& Adaptation::step() const {
   RTC_DCHECK_EQ(status_, Status::kValid);
   return step_.value();
 }

 // VideoSourceRestrictor is responsible for keeping track of current
 // VideoSourceRestrictions.
 class VideoStreamAdapter::VideoSourceRestrictor {
  public:
   VideoSourceRestrictor() {}

   VideoSourceRestrictions source_restrictions() const {
     return source_restrictions_;
   }
   const VideoAdaptationCounters& adaptation_counters() const {
     return adaptations_;
   }
   void ClearRestrictions() {
     source_restrictions_ = VideoSourceRestrictions();
     adaptations_ = VideoAdaptationCounters();
   }

   void set_min_pixels_per_frame(int min_pixels_per_frame) {
     min_pixels_per_frame_ = min_pixels_per_frame;
   }

   int min_pixels_per_frame() const { return min_pixels_per_frame_; }

   bool CanDecreaseResolutionTo(int target_pixels) {
     int max_pixels_per_frame = rtc::dchecked_cast<int>(
         source_restrictions_.max_pixels_per_frame().value_or(
             std::numeric_limits<int>::max()));
     return target_pixels < max_pixels_per_frame &&
            target_pixels >= min_pixels_per_frame_;
   }

   bool CanIncreaseResolutionTo(int target_pixels) {
     int max_pixels_wanted = GetIncreasedMaxPixelsWanted(target_pixels);
     int max_pixels_per_frame = rtc::dchecked_cast<int>(
         source_restrictions_.max_pixels_per_frame().value_or(
             std::numeric_limits<int>::max()));
     return max_pixels_wanted > max_pixels_per_frame;
   }

   bool CanDecreaseFrameRateTo(int max_frame_rate) {
     const int fps_wanted = std::max(kMinFrameRateFps, max_frame_rate);
     return fps_wanted < rtc::dchecked_cast<int>(
                             source_restrictions_.max_frame_rate().value_or(
                                 std::numeric_limits<int>::max()));
   }

   bool CanIncreaseFrameRateTo(int max_frame_rate) {
     return max_frame_rate > rtc::dchecked_cast<int>(
                                 source_restrictions_.max_frame_rate().value_or(
                                     std::numeric_limits<int>::max()));
   }

   void ApplyAdaptationStep(const Adaptation::Step& step,
                            DegradationPreference degradation_preference) {
     switch (step.type) {
       case Adaptation::StepType::kIncreaseResolution:
         IncreaseResolutionTo(step.target);
         break;
       case Adaptation::StepType::kDecreaseResolution:
         DecreaseResolutionTo(step.target);
         break;
       case Adaptation::StepType::kIncreaseFrameRate:
         IncreaseFrameRateTo(step.target);
         // TODO(https://crbug.com/webrtc/11222): Don't adapt in two steps.
         // GetAdaptationUp() should tell us the correct value, but BALANCED
         // logic in DecrementFramerate() makes it hard to predict whether this
         // will be the last step. Remove the dependency on
         // adaptation_counters().
         if (degradation_preference == DegradationPreference::BALANCED &&
             adaptation_counters().fps_adaptations == 0 &&
             step.target != std::numeric_limits<int>::max()) {
           RTC_LOG(LS_INFO) << "Removing framerate down-scaling setting.";
           IncreaseFrameRateTo(std::numeric_limits<int>::max());
         }
         break;
       case Adaptation::StepType::kDecreaseFrameRate:
         DecreaseFrameRateTo(step.target);
         break;
     }
   }

  private:
   static int GetIncreasedMaxPixelsWanted(int target_pixels) {
     if (target_pixels == std::numeric_limits<int>::max())
       return std::numeric_limits<int>::max();
     // When we decrease resolution, we go down to at most 3/5 of current pixels.
     // Thus to increase resolution, we need 3/5 to get back to where we started.
     // When going up, the desired max_pixels_per_frame() has to be significantly
     // higher than the target because the source's native resolutions might not
     // match the target. We pick 12/5 of the target.
     //
     // (This value was historically 4 times the old target, which is (3/5)*4 of
     // the new target - or 12/5 - assuming the target is adjusted according to
     // the above steps.)
     RTC_DCHECK(target_pixels != std::numeric_limits<int>::max());
     return (target_pixels * 12) / 5;
   }

   void DecreaseResolutionTo(int target_pixels) {
     RTC_DCHECK(CanDecreaseResolutionTo(target_pixels));
     RTC_LOG(LS_INFO) << "Scaling down resolution, max pixels: "
                      << target_pixels;
     source_restrictions_.set_max_pixels_per_frame(
         target_pixels != std::numeric_limits<int>::max()
             ? absl::optional<size_t>(target_pixels)
             : absl::nullopt);
     source_restrictions_.set_target_pixels_per_frame(absl::nullopt);
     ++adaptations_.resolution_adaptations;
   }

   void IncreaseResolutionTo(int target_pixels) {
     RTC_DCHECK(CanIncreaseResolutionTo(target_pixels));
     int max_pixels_wanted = GetIncreasedMaxPixelsWanted(target_pixels);
     RTC_LOG(LS_INFO) << "Scaling up resolution, max pixels: "
                      << max_pixels_wanted;
     source_restrictions_.set_max_pixels_per_frame(
         max_pixels_wanted != std::numeric_limits<int>::max()
             ? absl::optional<size_t>(max_pixels_wanted)
             : absl::nullopt);
     source_restrictions_.set_target_pixels_per_frame(
         max_pixels_wanted != std::numeric_limits<int>::max()
             ? absl::optional<size_t>(target_pixels)
             : absl::nullopt);
     --adaptations_.resolution_adaptations;
     RTC_DCHECK_GE(adaptations_.resolution_adaptations, 0);
   }

   void DecreaseFrameRateTo(int max_frame_rate) {
     RTC_DCHECK(CanDecreaseFrameRateTo(max_frame_rate));
     max_frame_rate = std::max(kMinFrameRateFps, max_frame_rate);
     RTC_LOG(LS_INFO) << "Scaling down framerate: " << max_frame_rate;
     source_restrictions_.set_max_frame_rate(
         max_frame_rate != std::numeric_limits<int>::max()
             ? absl::optional<double>(max_frame_rate)
             : absl::nullopt);
     ++adaptations_.fps_adaptations;
   }

   void IncreaseFrameRateTo(int max_frame_rate) {
     RTC_DCHECK(CanIncreaseFrameRateTo(max_frame_rate));
     RTC_LOG(LS_INFO) << "Scaling up framerate: " << max_frame_rate;
     source_restrictions_.set_max_frame_rate(
         max_frame_rate != std::numeric_limits<int>::max()
             ? absl::optional<double>(max_frame_rate)
             : absl::nullopt);
     --adaptations_.fps_adaptations;
     RTC_DCHECK_GE(adaptations_.fps_adaptations, 0);
   }

   // Needed by CanDecreaseResolutionTo().
   int min_pixels_per_frame_ = 0;
   // Current State.
   VideoSourceRestrictions source_restrictions_;
   VideoAdaptationCounters adaptations_;
 };

 // static
 VideoStreamAdapter::AdaptationRequest::Mode
 VideoStreamAdapter::AdaptationRequest::GetModeFromAdaptationAction(
     Adaptation::StepType step_type) {
   switch (step_type) {
     case Adaptation::StepType::kIncreaseResolution:
       return AdaptationRequest::Mode::kAdaptUp;
     case Adaptation::StepType::kDecreaseResolution:
       return AdaptationRequest::Mode::kAdaptDown;
     case Adaptation::StepType::kIncreaseFrameRate:
       return AdaptationRequest::Mode::kAdaptUp;
     case Adaptation::StepType::kDecreaseFrameRate:
       return AdaptationRequest::Mode::kAdaptDown;
   }
 }

 VideoStreamAdapter::VideoStreamAdapter()
     : source_restrictor_(std::make_unique<VideoSourceRestrictor>()),
       balanced_settings_(),
       adaptation_validation_id_(0),
       degradation_preference_(DegradationPreference::DISABLED),
       input_state_(),
       last_adaptation_request_(absl::nullopt) {}

 VideoStreamAdapter::~VideoStreamAdapter() {}

 VideoSourceRestrictions VideoStreamAdapter::source_restrictions() const {
   return source_restrictor_->source_restrictions();
 }

 const VideoAdaptationCounters& VideoStreamAdapter::adaptation_counters() const {
   return source_restrictor_->adaptation_counters();
 }

 const BalancedDegradationSettings& VideoStreamAdapter::balanced_settings()
     const {
   return balanced_settings_;
 }

 void VideoStreamAdapter::ClearRestrictions() {
   // Invalidate any previously returned Adaptation.
   ++adaptation_validation_id_;
   source_restrictor_->ClearRestrictions();
   last_adaptation_request_.reset();
 }

 void VideoStreamAdapter::SetDegradationPreference(
     DegradationPreference degradation_preference) {
   if (degradation_preference_ == degradation_preference)
     return;
   // Invalidate any previously returned Adaptation.
   ++adaptation_validation_id_;
   if (degradation_preference == DegradationPreference::BALANCED ||
       degradation_preference_ == DegradationPreference::BALANCED) {
     ClearRestrictions();
   }
   degradation_preference_ = degradation_preference;
 }

 void VideoStreamAdapter::SetInput(VideoStreamInputState input_state) {
   // Invalidate any previously returned Adaptation.
   ++adaptation_validation_id_;
   input_state_ = input_state;
   source_restrictor_->set_min_pixels_per_frame(
       input_state_.min_pixels_per_frame());
 }

 Adaptation VideoStreamAdapter::GetAdaptationUp() const {
   RTC_DCHECK_NE(degradation_preference_, DegradationPreference::DISABLED);
   RTC_DCHECK(input_state_.HasInputFrameSizeAndFramesPerSecond());
   // Don't adapt if we're awaiting a previous adaptation to have an effect.
   bool last_adaptation_was_up =
       last_adaptation_request_ &&
       last_adaptation_request_->mode_ == AdaptationRequest::Mode::kAdaptUp;
   if (last_adaptation_was_up &&
       degradation_preference_ == DegradationPreference::MAINTAIN_FRAMERATE &&
       input_state_.frame_size_pixels().value() <=
           last_adaptation_request_->input_pixel_count_) {
     return Adaptation(adaptation_validation_id_,
                       Adaptation::Status::kAwaitingPreviousAdaptation);
   }

   // Maybe propose targets based on degradation preference.
   switch (degradation_preference_) {
     case DegradationPreference::BALANCED: {
       // Attempt to increase target frame rate.
       int target_fps =
           balanced_settings_.MaxFps(input_state_.video_codec_type(),
                                     input_state_.frame_size_pixels().value());
       if (source_restrictor_->CanIncreaseFrameRateTo(target_fps)) {
         return Adaptation(
             adaptation_validation_id_,
             Adaptation::Step(Adaptation::StepType::kIncreaseFrameRate,
                              target_fps));
       }
       // Scale up resolution.
       ABSL_FALLTHROUGH_INTENDED;
     }
     case DegradationPreference::MAINTAIN_FRAMERATE: {
       // Attempt to increase pixel count.
       int target_pixels = input_state_.frame_size_pixels().value();
       if (source_restrictor_->adaptation_counters().resolution_adaptations ==
           1) {
         RTC_LOG(LS_INFO) << "Removing resolution down-scaling setting.";
         target_pixels = std::numeric_limits<int>::max();
       }
       target_pixels = GetHigherResolutionThan(target_pixels);
       if (!source_restrictor_->CanIncreaseResolutionTo(target_pixels)) {
         return Adaptation(adaptation_validation_id_,
                           Adaptation::Status::kLimitReached);
       }
       return Adaptation(
           adaptation_validation_id_,
           Adaptation::Step(Adaptation::StepType::kIncreaseResolution,
                            target_pixels));
     }
     case DegradationPreference::MAINTAIN_RESOLUTION: {
       // Scale up framerate.
       int target_fps = input_state_.frames_per_second().value();
       if (source_restrictor_->adaptation_counters().fps_adaptations == 1) {
         RTC_LOG(LS_INFO) << "Removing framerate down-scaling setting.";
         target_fps = std::numeric_limits<int>::max();
       }
       target_fps = GetHigherFrameRateThan(target_fps);
       if (!source_restrictor_->CanIncreaseFrameRateTo(target_fps)) {
         return Adaptation(adaptation_validation_id_,
                           Adaptation::Status::kLimitReached);
       }
       return Adaptation(
           adaptation_validation_id_,
           Adaptation::Step(Adaptation::StepType::kIncreaseFrameRate,
                            target_fps));
     }
     case DegradationPreference::DISABLED:
       RTC_NOTREACHED();
       return Adaptation(adaptation_validation_id_,
                         Adaptation::Status::kLimitReached);
   }
 }

 Adaptation VideoStreamAdapter::GetAdaptationDown() const {
   RTC_DCHECK_NE(degradation_preference_, DegradationPreference::DISABLED);
   RTC_DCHECK(input_state_.HasInputFrameSizeAndFramesPerSecond());
   // Don't adapt adaptation is disabled.
   bool last_adaptation_was_down =
       last_adaptation_request_ &&
       last_adaptation_request_->mode_ == AdaptationRequest::Mode::kAdaptDown;
   // Don't adapt if we're awaiting a previous adaptation to have an effect.
   if (last_adaptation_was_down &&
       degradation_preference_ == DegradationPreference::MAINTAIN_FRAMERATE &&
       input_state_.frame_size_pixels().value() >=
           last_adaptation_request_->input_pixel_count_) {
     return Adaptation(adaptation_validation_id_,
                       Adaptation::Status::kAwaitingPreviousAdaptation);
   }

   // Maybe propose targets based on degradation preference.
   switch (degradation_preference_) {
     case DegradationPreference::BALANCED: {
       // Try scale down framerate, if lower.
       int target_fps =
           balanced_settings_.MinFps(input_state_.video_codec_type(),
                                     input_state_.frame_size_pixels().value());
       if (source_restrictor_->CanDecreaseFrameRateTo(target_fps)) {
         return Adaptation(
             adaptation_validation_id_,
             Adaptation::Step(Adaptation::StepType::kDecreaseFrameRate,
                              target_fps));
       }
       // Scale down resolution.
       ABSL_FALLTHROUGH_INTENDED;
     }
     case DegradationPreference::MAINTAIN_FRAMERATE: {
       // Scale down resolution.
       int target_pixels =
           GetLowerResolutionThan(input_state_.frame_size_pixels().value());
       bool min_pixel_limit_reached =
           target_pixels < source_restrictor_->min_pixels_per_frame();
       if (!source_restrictor_->CanDecreaseResolutionTo(target_pixels)) {
         return Adaptation(adaptation_validation_id_,
                           Adaptation::Status::kLimitReached,
                           min_pixel_limit_reached);
       }
       return Adaptation(
           adaptation_validation_id_,
           Adaptation::Step(Adaptation::StepType::kDecreaseResolution,
                            target_pixels),
           min_pixel_limit_reached);
     }
     case DegradationPreference::MAINTAIN_RESOLUTION: {
       int target_fps =
           GetLowerFrameRateThan(input_state_.frames_per_second().value());
       if (!source_restrictor_->CanDecreaseFrameRateTo(target_fps)) {
         return Adaptation(adaptation_validation_id_,
                           Adaptation::Status::kLimitReached);
       }
       return Adaptation(
           adaptation_validation_id_,
           Adaptation::Step(Adaptation::StepType::kDecreaseFrameRate,
                            target_fps));
     }
     case DegradationPreference::DISABLED:
       RTC_NOTREACHED();
       return Adaptation(adaptation_validation_id_,
                         Adaptation::Status::kLimitReached);
   }
 }

 VideoSourceRestrictions VideoStreamAdapter::PeekNextRestrictions(
     const Adaptation& adaptation) const {
   RTC_DCHECK_EQ(adaptation.validation_id_, adaptation_validation_id_);
   if (adaptation.status() != Adaptation::Status::kValid)
     return source_restrictor_->source_restrictions();
   VideoSourceRestrictor restrictor_copy = *source_restrictor_;
   restrictor_copy.ApplyAdaptationStep(adaptation.step(),
                                       degradation_preference_);
   return restrictor_copy.source_restrictions();
 }

 ResourceListenerResponse VideoStreamAdapter::ApplyAdaptation(
     const Adaptation& adaptation) {
   RTC_DCHECK_EQ(adaptation.validation_id_, adaptation_validation_id_);
   if (adaptation.status() != Adaptation::Status::kValid) {
     return ResourceListenerResponse::kNothing;
   }
   // Remember the input pixels and fps of this adaptation. Used to avoid
   // adapting again before this adaptation has had an effect.
   last_adaptation_request_.emplace(AdaptationRequest{
       input_state_.frame_size_pixels().value(),
       input_state_.frames_per_second().value(),
       AdaptationRequest::GetModeFromAdaptationAction(adaptation.step().type)});
   // Adapt!
   source_restrictor_->ApplyAdaptationStep(adaptation.step(),
                                           degradation_preference_);
   // In BALANCED, if requested FPS is higher or close to input FPS to the target
   // we tell the QualityScaler to increase its frequency.
   // TODO(hbos): Don't have QualityScaler-specific logic here. If the
   // QualityScaler wants to add special logic depending on what effects
   // adaptation had, it should listen to changes to the VideoSourceRestrictions
   // instead.
   if (degradation_preference_ == DegradationPreference::BALANCED &&
       adaptation.step().type == Adaptation::StepType::kDecreaseFrameRate) {
     absl::optional<int> min_diff =
         balanced_settings_.MinFpsDiff(input_state_.frame_size_pixels().value());
     if (min_diff && input_state_.frames_per_second().value() > 0) {
       int fps_diff =
           input_state_.frames_per_second().value() - adaptation.step().target;
       if (fps_diff < min_diff.value()) {
         return ResourceListenerResponse::kQualityScalerShouldIncreaseFrequency;
       }
     }
   }
   return ResourceListenerResponse::kNothing;
 }

 }  // namespace webrtc
	/*
	* Copyright 2020 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 "call/adaptation/video_stream_adapter.h"

	#include <algorithm>
	#include <limits>
	#include <utility>

	#include "absl/types/optional.h"
	#include "api/video/video_adaptation_reason.h"
	#include "api/video_codecs/video_encoder.h"
	#include "rtc_base/constructor_magic.h"
	#include "rtc_base/logging.h"
	#include "rtc_base/numerics/safe_conversions.h"

	namespace webrtc {

	const int kMinFrameRateFps = 2;

	namespace {

	// Generate suggested higher and lower frame rates and resolutions, to be
	// applied to the VideoSourceRestrictor. These are used in "maintain-resolution"
	// and "maintain-framerate". The "balanced" degradation preference also makes
	// use of BalancedDegradationPreference when generating suggestions. The
	// VideoSourceRestrictor decidedes whether or not a proposed adaptation is
	// valid.

	// For frame rate, the steps we take are 2/3 (down) and 3/2 (up).
	int GetLowerFrameRateThan(int fps) {
	RTC_DCHECK(fps != std::numeric_limits<int>::max());
	return (fps * 2) / 3;
	}
	// TODO(hbos): Use absl::optional<> instead?
	int GetHigherFrameRateThan(int fps) {
	return fps != std::numeric_limits<int>::max()
	? (fps * 3) / 2
	: std::numeric_limits<int>::max();
	}

	// For resolution, the steps we take are 3/5 (down) and 5/3 (up).
	// Notice the asymmetry of which restriction property is set depending on if
	// we are adapting up or down:
	// - VideoSourceRestrictor::DecreaseResolution() sets the max_pixels_per_frame()
	// to the desired target and target_pixels_per_frame() to null.
	// - VideoSourceRestrictor::IncreaseResolutionTo() sets the
	// target_pixels_per_frame() to the desired target, and max_pixels_per_frame()
	// is set according to VideoSourceRestrictor::GetIncreasedMaxPixelsWanted().
	int GetLowerResolutionThan(int pixel_count) {
	RTC_DCHECK(pixel_count != std::numeric_limits<int>::max());
	return (pixel_count * 3) / 5;
	}

	} // namespace

	VideoSourceRestrictions FilterRestrictionsByDegradationPreference(
	VideoSourceRestrictions source_restrictions,
	DegradationPreference degradation_preference) {
	switch (degradation_preference) {
	case DegradationPreference::BALANCED:
	break;
	case DegradationPreference::MAINTAIN_FRAMERATE:
	source_restrictions.set_max_frame_rate(absl::nullopt);
	break;
	case DegradationPreference::MAINTAIN_RESOLUTION:
	source_restrictions.set_max_pixels_per_frame(absl::nullopt);
	source_restrictions.set_target_pixels_per_frame(absl::nullopt);
	break;
	case DegradationPreference::DISABLED:
	source_restrictions.set_max_pixels_per_frame(absl::nullopt);
	source_restrictions.set_target_pixels_per_frame(absl::nullopt);
	source_restrictions.set_max_frame_rate(absl::nullopt);
	}
	return source_restrictions;
	}

	VideoAdaptationCounters FilterVideoAdaptationCountersByDegradationPreference(
	VideoAdaptationCounters counters,
	DegradationPreference degradation_preference) {
	switch (degradation_preference) {
	case DegradationPreference::BALANCED:
	break;
	case DegradationPreference::MAINTAIN_FRAMERATE:
	counters.fps_adaptations = 0;
	break;
	case DegradationPreference::MAINTAIN_RESOLUTION:
	counters.resolution_adaptations = 0;
	break;
	case DegradationPreference::DISABLED:
	counters.resolution_adaptations = 0;
	counters.fps_adaptations = 0;
	break;
	default:
	RTC_NOTREACHED();
	}
	return counters;
	}

	// TODO(hbos): Use absl::optional<> instead?
	int GetHigherResolutionThan(int pixel_count) {
	return pixel_count != std::numeric_limits<int>::max()
	? (pixel_count * 5) / 3
	: std::numeric_limits<int>::max();
	}

	Adaptation::Step::Step(StepType type, int target)
	: type(type), target(target) {}

	Adaptation::Adaptation(int validation_id, Step step)
	: validation_id_(validation_id),
	status_(Status::kValid),
	step_(std::move(step)),
	min_pixel_limit_reached_(false) {}

	Adaptation::Adaptation(int validation_id,
	Step step,
	bool min_pixel_limit_reached)
	: validation_id_(validation_id),
	status_(Status::kValid),
	step_(std::move(step)),
	min_pixel_limit_reached_(min_pixel_limit_reached) {}

	Adaptation::Adaptation(int validation_id, Status invalid_status)
	: validation_id_(validation_id),
	status_(invalid_status),
	step_(absl::nullopt),
	min_pixel_limit_reached_(false) {
	RTC_DCHECK_NE(status_, Status::kValid);
	}

	Adaptation::Adaptation(int validation_id,
	Status invalid_status,
	bool min_pixel_limit_reached)
	: validation_id_(validation_id),
	status_(invalid_status),
	step_(absl::nullopt),
	min_pixel_limit_reached_(min_pixel_limit_reached) {
	RTC_DCHECK_NE(status_, Status::kValid);
	}

	Adaptation::Status Adaptation::status() const {
	return status_;
	}

	bool Adaptation::min_pixel_limit_reached() const {
	return min_pixel_limit_reached_;
	}

	const Adaptation::Step& Adaptation::step() const {
	RTC_DCHECK_EQ(status_, Status::kValid);
	return step_.value();
	}

	// VideoSourceRestrictor is responsible for keeping track of current
	// VideoSourceRestrictions.
	class VideoStreamAdapter::VideoSourceRestrictor {
	public:
	VideoSourceRestrictor() {}

	VideoSourceRestrictions source_restrictions() const {
	return source_restrictions_;
	}
	const VideoAdaptationCounters& adaptation_counters() const {
	return adaptations_;
	}
	void ClearRestrictions() {
	source_restrictions_ = VideoSourceRestrictions();
	adaptations_ = VideoAdaptationCounters();
	}

	void set_min_pixels_per_frame(int min_pixels_per_frame) {
	min_pixels_per_frame_ = min_pixels_per_frame;
	}

	int min_pixels_per_frame() const { return min_pixels_per_frame_; }

	bool CanDecreaseResolutionTo(int target_pixels) {
	int max_pixels_per_frame = rtc::dchecked_cast<int>(
	source_restrictions_.max_pixels_per_frame().value_or(
	std::numeric_limits<int>::max()));
	return target_pixels < max_pixels_per_frame &&
	target_pixels >= min_pixels_per_frame_;
	}

	bool CanIncreaseResolutionTo(int target_pixels) {
	int max_pixels_wanted = GetIncreasedMaxPixelsWanted(target_pixels);
	int max_pixels_per_frame = rtc::dchecked_cast<int>(
	source_restrictions_.max_pixels_per_frame().value_or(
	std::numeric_limits<int>::max()));
	return max_pixels_wanted > max_pixels_per_frame;
	}

	bool CanDecreaseFrameRateTo(int max_frame_rate) {
	const int fps_wanted = std::max(kMinFrameRateFps, max_frame_rate);
	return fps_wanted < rtc::dchecked_cast<int>(
	source_restrictions_.max_frame_rate().value_or(
	std::numeric_limits<int>::max()));
	}

	bool CanIncreaseFrameRateTo(int max_frame_rate) {
	return max_frame_rate > rtc::dchecked_cast<int>(
	source_restrictions_.max_frame_rate().value_or(
	std::numeric_limits<int>::max()));
	}

	void ApplyAdaptationStep(const Adaptation::Step& step,
	DegradationPreference degradation_preference) {
	switch (step.type) {
	case Adaptation::StepType::kIncreaseResolution:
	IncreaseResolutionTo(step.target);
	break;
	case Adaptation::StepType::kDecreaseResolution:
	DecreaseResolutionTo(step.target);
	break;
	case Adaptation::StepType::kIncreaseFrameRate:
	IncreaseFrameRateTo(step.target);
	// TODO(https://crbug.com/webrtc/11222): Don't adapt in two steps.
	// GetAdaptationUp() should tell us the correct value, but BALANCED
	// logic in DecrementFramerate() makes it hard to predict whether this
	// will be the last step. Remove the dependency on
	// adaptation_counters().
	if (degradation_preference == DegradationPreference::BALANCED &&
	adaptation_counters().fps_adaptations == 0 &&
	step.target != std::numeric_limits<int>::max()) {
	RTC_LOG(LS_INFO) << "Removing framerate down-scaling setting.";
	IncreaseFrameRateTo(std::numeric_limits<int>::max());
	}
	break;
	case Adaptation::StepType::kDecreaseFrameRate:
	DecreaseFrameRateTo(step.target);
	break;
	}
	}

	private:
	static int GetIncreasedMaxPixelsWanted(int target_pixels) {
	if (target_pixels == std::numeric_limits<int>::max())
	return std::numeric_limits<int>::max();
	// When we decrease resolution, we go down to at most 3/5 of current pixels.
	// Thus to increase resolution, we need 3/5 to get back to where we started.
	// When going up, the desired max_pixels_per_frame() has to be significantly
	// higher than the target because the source's native resolutions might not
	// match the target. We pick 12/5 of the target.
	//
	// (This value was historically 4 times the old target, which is (3/5)*4 of
	// the new target - or 12/5 - assuming the target is adjusted according to
	// the above steps.)
	RTC_DCHECK(target_pixels != std::numeric_limits<int>::max());
	return (target_pixels * 12) / 5;
	}

	void DecreaseResolutionTo(int target_pixels) {
	RTC_DCHECK(CanDecreaseResolutionTo(target_pixels));
	RTC_LOG(LS_INFO) << "Scaling down resolution, max pixels: "
	<< target_pixels;
	source_restrictions_.set_max_pixels_per_frame(
	target_pixels != std::numeric_limits<int>::max()
	? absl::optional<size_t>(target_pixels)
	: absl::nullopt);
	source_restrictions_.set_target_pixels_per_frame(absl::nullopt);
	++adaptations_.resolution_adaptations;
	}

	void IncreaseResolutionTo(int target_pixels) {
	RTC_DCHECK(CanIncreaseResolutionTo(target_pixels));
	int max_pixels_wanted = GetIncreasedMaxPixelsWanted(target_pixels);
	RTC_LOG(LS_INFO) << "Scaling up resolution, max pixels: "
	<< max_pixels_wanted;
	source_restrictions_.set_max_pixels_per_frame(
	max_pixels_wanted != std::numeric_limits<int>::max()
	? absl::optional<size_t>(max_pixels_wanted)
	: absl::nullopt);
	source_restrictions_.set_target_pixels_per_frame(
	max_pixels_wanted != std::numeric_limits<int>::max()
	? absl::optional<size_t>(target_pixels)
	: absl::nullopt);
	--adaptations_.resolution_adaptations;
	RTC_DCHECK_GE(adaptations_.resolution_adaptations, 0);
	}

	void DecreaseFrameRateTo(int max_frame_rate) {
	RTC_DCHECK(CanDecreaseFrameRateTo(max_frame_rate));
	max_frame_rate = std::max(kMinFrameRateFps, max_frame_rate);
	RTC_LOG(LS_INFO) << "Scaling down framerate: " << max_frame_rate;
	source_restrictions_.set_max_frame_rate(
	max_frame_rate != std::numeric_limits<int>::max()
	? absl::optional<double>(max_frame_rate)
	: absl::nullopt);
	++adaptations_.fps_adaptations;
	}

	void IncreaseFrameRateTo(int max_frame_rate) {
	RTC_DCHECK(CanIncreaseFrameRateTo(max_frame_rate));
	RTC_LOG(LS_INFO) << "Scaling up framerate: " << max_frame_rate;
	source_restrictions_.set_max_frame_rate(
	max_frame_rate != std::numeric_limits<int>::max()
	? absl::optional<double>(max_frame_rate)
	: absl::nullopt);
	--adaptations_.fps_adaptations;
	RTC_DCHECK_GE(adaptations_.fps_adaptations, 0);
	}

	// Needed by CanDecreaseResolutionTo().
	int min_pixels_per_frame_ = 0;
	// Current State.
	VideoSourceRestrictions source_restrictions_;
	VideoAdaptationCounters adaptations_;
	};

	// static
	VideoStreamAdapter::AdaptationRequest::Mode
	VideoStreamAdapter::AdaptationRequest::GetModeFromAdaptationAction(
	Adaptation::StepType step_type) {
	switch (step_type) {
	case Adaptation::StepType::kIncreaseResolution:
	return AdaptationRequest::Mode::kAdaptUp;
	case Adaptation::StepType::kDecreaseResolution:
	return AdaptationRequest::Mode::kAdaptDown;
	case Adaptation::StepType::kIncreaseFrameRate:
	return AdaptationRequest::Mode::kAdaptUp;
	case Adaptation::StepType::kDecreaseFrameRate:
	return AdaptationRequest::Mode::kAdaptDown;
	}
	}

	VideoStreamAdapter::VideoStreamAdapter()
	: source_restrictor_(std::make_unique<VideoSourceRestrictor>()),
	balanced_settings_(),
	adaptation_validation_id_(0),
	degradation_preference_(DegradationPreference::DISABLED),
	input_state_(),
	last_adaptation_request_(absl::nullopt) {}

	VideoStreamAdapter::~VideoStreamAdapter() {}

	VideoSourceRestrictions VideoStreamAdapter::source_restrictions() const {
	return source_restrictor_->source_restrictions();
	}

	const VideoAdaptationCounters& VideoStreamAdapter::adaptation_counters() const {
	return source_restrictor_->adaptation_counters();
	}

	const BalancedDegradationSettings& VideoStreamAdapter::balanced_settings()
	const {
	return balanced_settings_;
	}

	void VideoStreamAdapter::ClearRestrictions() {
	// Invalidate any previously returned Adaptation.
	++adaptation_validation_id_;
	source_restrictor_->ClearRestrictions();
	last_adaptation_request_.reset();
	}

	void VideoStreamAdapter::SetDegradationPreference(
	DegradationPreference degradation_preference) {
	if (degradation_preference_ == degradation_preference)
	return;
	// Invalidate any previously returned Adaptation.
	++adaptation_validation_id_;
	if (degradation_preference == DegradationPreference::BALANCED \|\|
	degradation_preference_ == DegradationPreference::BALANCED) {
	ClearRestrictions();
	}
	degradation_preference_ = degradation_preference;
	}

	void VideoStreamAdapter::SetInput(VideoStreamInputState input_state) {
	// Invalidate any previously returned Adaptation.
	++adaptation_validation_id_;
	input_state_ = input_state;
	source_restrictor_->set_min_pixels_per_frame(
	input_state_.min_pixels_per_frame());
	}

	Adaptation VideoStreamAdapter::GetAdaptationUp() const {
	RTC_DCHECK_NE(degradation_preference_, DegradationPreference::DISABLED);
	RTC_DCHECK(input_state_.HasInputFrameSizeAndFramesPerSecond());
	// Don't adapt if we're awaiting a previous adaptation to have an effect.
	bool last_adaptation_was_up =
	last_adaptation_request_ &&
	last_adaptation_request_->mode_ == AdaptationRequest::Mode::kAdaptUp;
	if (last_adaptation_was_up &&
	degradation_preference_ == DegradationPreference::MAINTAIN_FRAMERATE &&
	input_state_.frame_size_pixels().value() <=
	last_adaptation_request_->input_pixel_count_) {
	return Adaptation(adaptation_validation_id_,
	Adaptation::Status::kAwaitingPreviousAdaptation);
	}

	// Maybe propose targets based on degradation preference.
	switch (degradation_preference_) {
	case DegradationPreference::BALANCED: {
	// Attempt to increase target frame rate.
	int target_fps =
	balanced_settings_.MaxFps(input_state_.video_codec_type(),
	input_state_.frame_size_pixels().value());
	if (source_restrictor_->CanIncreaseFrameRateTo(target_fps)) {
	return Adaptation(
	adaptation_validation_id_,
	Adaptation::Step(Adaptation::StepType::kIncreaseFrameRate,
	target_fps));
	}
	// Scale up resolution.
	ABSL_FALLTHROUGH_INTENDED;
	}
	case DegradationPreference::MAINTAIN_FRAMERATE: {
	// Attempt to increase pixel count.
	int target_pixels = input_state_.frame_size_pixels().value();
	if (source_restrictor_->adaptation_counters().resolution_adaptations ==
	1) {
	RTC_LOG(LS_INFO) << "Removing resolution down-scaling setting.";
	target_pixels = std::numeric_limits<int>::max();
	}
	target_pixels = GetHigherResolutionThan(target_pixels);
	if (!source_restrictor_->CanIncreaseResolutionTo(target_pixels)) {
	return Adaptation(adaptation_validation_id_,
	Adaptation::Status::kLimitReached);
	}
	return Adaptation(
	adaptation_validation_id_,
	Adaptation::Step(Adaptation::StepType::kIncreaseResolution,
	target_pixels));
	}
	case DegradationPreference::MAINTAIN_RESOLUTION: {
	// Scale up framerate.
	int target_fps = input_state_.frames_per_second().value();
	if (source_restrictor_->adaptation_counters().fps_adaptations == 1) {
	RTC_LOG(LS_INFO) << "Removing framerate down-scaling setting.";
	target_fps = std::numeric_limits<int>::max();
	}
	target_fps = GetHigherFrameRateThan(target_fps);
	if (!source_restrictor_->CanIncreaseFrameRateTo(target_fps)) {
	return Adaptation(adaptation_validation_id_,
	Adaptation::Status::kLimitReached);
	}
	return Adaptation(
	adaptation_validation_id_,
	Adaptation::Step(Adaptation::StepType::kIncreaseFrameRate,
	target_fps));
	}
	case DegradationPreference::DISABLED:
	RTC_NOTREACHED();
	return Adaptation(adaptation_validation_id_,
	Adaptation::Status::kLimitReached);
	}
	}

	Adaptation VideoStreamAdapter::GetAdaptationDown() const {
	RTC_DCHECK_NE(degradation_preference_, DegradationPreference::DISABLED);
	RTC_DCHECK(input_state_.HasInputFrameSizeAndFramesPerSecond());
	// Don't adapt adaptation is disabled.
	bool last_adaptation_was_down =
	last_adaptation_request_ &&
	last_adaptation_request_->mode_ == AdaptationRequest::Mode::kAdaptDown;
	// Don't adapt if we're awaiting a previous adaptation to have an effect.
	if (last_adaptation_was_down &&
	degradation_preference_ == DegradationPreference::MAINTAIN_FRAMERATE &&
	input_state_.frame_size_pixels().value() >=
	last_adaptation_request_->input_pixel_count_) {
	return Adaptation(adaptation_validation_id_,
	Adaptation::Status::kAwaitingPreviousAdaptation);
	}

	// Maybe propose targets based on degradation preference.
	switch (degradation_preference_) {
	case DegradationPreference::BALANCED: {
	// Try scale down framerate, if lower.
	int target_fps =
	balanced_settings_.MinFps(input_state_.video_codec_type(),
	input_state_.frame_size_pixels().value());
	if (source_restrictor_->CanDecreaseFrameRateTo(target_fps)) {
	return Adaptation(
	adaptation_validation_id_,
	Adaptation::Step(Adaptation::StepType::kDecreaseFrameRate,
	target_fps));
	}
	// Scale down resolution.
	ABSL_FALLTHROUGH_INTENDED;
	}
	case DegradationPreference::MAINTAIN_FRAMERATE: {
	// Scale down resolution.
	int target_pixels =
	GetLowerResolutionThan(input_state_.frame_size_pixels().value());
	bool min_pixel_limit_reached =
	target_pixels < source_restrictor_->min_pixels_per_frame();
	if (!source_restrictor_->CanDecreaseResolutionTo(target_pixels)) {
	return Adaptation(adaptation_validation_id_,
	Adaptation::Status::kLimitReached,
	min_pixel_limit_reached);
	}
	return Adaptation(
	adaptation_validation_id_,
	Adaptation::Step(Adaptation::StepType::kDecreaseResolution,
	target_pixels),
	min_pixel_limit_reached);
	}
	case DegradationPreference::MAINTAIN_RESOLUTION: {
	int target_fps =
	GetLowerFrameRateThan(input_state_.frames_per_second().value());
	if (!source_restrictor_->CanDecreaseFrameRateTo(target_fps)) {
	return Adaptation(adaptation_validation_id_,
	Adaptation::Status::kLimitReached);
	}
	return Adaptation(
	adaptation_validation_id_,
	Adaptation::Step(Adaptation::StepType::kDecreaseFrameRate,
	target_fps));
	}
	case DegradationPreference::DISABLED:
	RTC_NOTREACHED();
	return Adaptation(adaptation_validation_id_,
	Adaptation::Status::kLimitReached);
	}
	}

	VideoSourceRestrictions VideoStreamAdapter::PeekNextRestrictions(
	const Adaptation& adaptation) const {
	RTC_DCHECK_EQ(adaptation.validation_id_, adaptation_validation_id_);
	if (adaptation.status() != Adaptation::Status::kValid)
	return source_restrictor_->source_restrictions();
	VideoSourceRestrictor restrictor_copy = *source_restrictor_;
	restrictor_copy.ApplyAdaptationStep(adaptation.step(),
	degradation_preference_);
	return restrictor_copy.source_restrictions();
	}

	ResourceListenerResponse VideoStreamAdapter::ApplyAdaptation(
	const Adaptation& adaptation) {
	RTC_DCHECK_EQ(adaptation.validation_id_, adaptation_validation_id_);
	if (adaptation.status() != Adaptation::Status::kValid) {
	return ResourceListenerResponse::kNothing;
	}
	// Remember the input pixels and fps of this adaptation. Used to avoid
	// adapting again before this adaptation has had an effect.
	last_adaptation_request_.emplace(AdaptationRequest{
	input_state_.frame_size_pixels().value(),
	input_state_.frames_per_second().value(),
	AdaptationRequest::GetModeFromAdaptationAction(adaptation.step().type)});
	// Adapt!
	source_restrictor_->ApplyAdaptationStep(adaptation.step(),
	degradation_preference_);
	// In BALANCED, if requested FPS is higher or close to input FPS to the target
	// we tell the QualityScaler to increase its frequency.
	// TODO(hbos): Don't have QualityScaler-specific logic here. If the
	// QualityScaler wants to add special logic depending on what effects
	// adaptation had, it should listen to changes to the VideoSourceRestrictions
	// instead.
	if (degradation_preference_ == DegradationPreference::BALANCED &&
	adaptation.step().type == Adaptation::StepType::kDecreaseFrameRate) {
	absl::optional<int> min_diff =
	balanced_settings_.MinFpsDiff(input_state_.frame_size_pixels().value());
	if (min_diff && input_state_.frames_per_second().value() > 0) {
	int fps_diff =
	input_state_.frames_per_second().value() - adaptation.step().target;
	if (fps_diff < min_diff.value()) {
	return ResourceListenerResponse::kQualityScalerShouldIncreaseFrequency;
	}
	}
	}
	return ResourceListenerResponse::kNothing;
	}

	} // namespace webrtc