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/*
* 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_;
};
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();
}
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_request_increased_resolution =
last_adaptation_request_ && last_adaptation_request_->step_type_ ==
Adaptation::StepType::kIncreaseResolution;
if (last_request_increased_resolution &&
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();
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 if we're awaiting a previous adaptation to have an effect or
// if we switched degradation preference.
bool last_request_decreased_resolution =
last_adaptation_request_ && last_adaptation_request_->step_type_ ==
Adaptation::StepType::kDecreaseResolution;
if (last_request_decreased_resolution &&
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());
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();
}
void VideoStreamAdapter::ApplyAdaptation(const Adaptation& adaptation) {
RTC_DCHECK_EQ(adaptation.validation_id_, adaptation_validation_id_);
if (adaptation.status() != Adaptation::Status::kValid)
return;
// 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(), adaptation.step().type});
// Adapt!
source_restrictor_->ApplyAdaptationStep(adaptation.step(),
degradation_preference_);
}
} // namespace webrtc