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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.
*/
#ifndef CALL_ADAPTATION_VIDEO_STREAM_ADAPTER_H_
#define CALL_ADAPTATION_VIDEO_STREAM_ADAPTER_H_
#include <memory>
#include "absl/types/optional.h"
#include "api/rtp_parameters.h"
#include "api/video/video_adaptation_counters.h"
#include "call/adaptation/resource.h"
#include "call/adaptation/video_source_restrictions.h"
#include "call/adaptation/video_stream_input_state.h"
#include "modules/video_coding/utility/quality_scaler.h"
#include "rtc_base/experiments/balanced_degradation_settings.h"
namespace webrtc {
class VideoStreamAdapter;
extern const int kMinFrameRateFps;
VideoSourceRestrictions FilterRestrictionsByDegradationPreference(
VideoSourceRestrictions source_restrictions,
DegradationPreference degradation_preference);
VideoAdaptationCounters FilterVideoAdaptationCountersByDegradationPreference(
VideoAdaptationCounters counters,
DegradationPreference degradation_preference);
int GetHigherResolutionThan(int pixel_count);
// Represents one step that the VideoStreamAdapter can take when adapting the
// VideoSourceRestrictions up or down. Or, if adaptation is not valid, provides
// a Status code indicating the reason for not adapting.
class Adaptation final {
public:
enum class Status {
// Applying this adaptation will have an effect. All other Status codes
// indicate that adaptation is not possible and why.
kValid,
// Cannot adapt. The minimum or maximum adaptation has already been reached.
// There are no more steps to take.
kLimitReached,
// Cannot adapt. The resolution or frame rate requested by a recent
// adaptation has not yet been reflected in the input resolution or frame
// rate; adaptation is refused to avoid "double-adapting".
kAwaitingPreviousAdaptation,
};
// The status of this Adaptation. To find out how this Adaptation affects
// VideoSourceRestrictions, see VideoStreamAdapter::PeekNextRestrictions().
Status status() const;
// Used for stats reporting.
bool min_pixel_limit_reached() const;
private:
// The adapter needs to know about step type and step target in order to
// construct and perform an Adaptation, which is a detail we do not want to
// expose to the public interface.
friend class VideoStreamAdapter;
enum class StepType {
kIncreaseResolution,
kDecreaseResolution,
kIncreaseFrameRate,
kDecreaseFrameRate,
};
struct Step {
Step(StepType type, int target);
const StepType type;
const int target; // Pixel or frame rate depending on |type|.
};
// Constructs with a valid adaptation Step. Status is kValid.
Adaptation(int validation_id, Step step);
Adaptation(int validation_id, Step step, bool min_pixel_limit_reached);
// Constructor when adaptation is not valid. Status MUST NOT be kValid.
Adaptation(int validation_id, Status invalid_status);
Adaptation(int validation_id,
Status invalid_status,
bool min_pixel_limit_reached);
const Step& step() const; // Only callable if |status_| is kValid.
// An Adaptation can become invalidated if the state of VideoStreamAdapter is
// modified before the Adaptation is applied. To guard against this, this ID
// has to match VideoStreamAdapter::adaptation_validation_id_ when applied.
const int validation_id_;
const Status status_;
const absl::optional<Step> step_; // Only present if |status_| is kValid.
const bool min_pixel_limit_reached_;
};
// Owns the VideoSourceRestriction for a single stream and is responsible for
// adapting it up or down when told to do so. This class serves the following
// purposes:
// 1. Keep track of a stream's restrictions.
// 2. Provide valid ways to adapt up or down the stream's restrictions.
// 3. Modify the stream's restrictions in one of the valid ways.
class VideoStreamAdapter {
public:
VideoStreamAdapter();
~VideoStreamAdapter();
VideoSourceRestrictions source_restrictions() const;
const VideoAdaptationCounters& adaptation_counters() const;
void ClearRestrictions();
// TODO(hbos): Setting the degradation preference should not clear
// restrictions! This is not defined in the spec and is unexpected, there is a
// tiny risk that people would discover and rely on this behavior.
void SetDegradationPreference(DegradationPreference degradation_preference);
// The adaptaiton logic depends on these inputs.
void SetInput(VideoStreamInputState input_state);
// Returns an adaptation that we are guaranteed to be able to apply, or a
// status code indicating the reason why we cannot adapt.
Adaptation GetAdaptationUp() const;
Adaptation GetAdaptationDown() const;
// Returns the restrictions that result from applying the adaptation, without
// actually applying it. If the adaptation is not valid, current restrictions
// are returned.
VideoSourceRestrictions PeekNextRestrictions(
const Adaptation& adaptation) const;
// Updates source_restrictions() based according to the Adaptation.
void ApplyAdaptation(const Adaptation& adaptation);
private:
class VideoSourceRestrictor;
// The input frame rate and resolution at the time of an adaptation in the
// direction described by |mode_| (up or down).
// TODO(https://crbug.com/webrtc/11393): Can this be renamed? Can this be
// merged with AdaptationTarget?
struct AdaptationRequest {
// The pixel count produced by the source at the time of the adaptation.
int input_pixel_count_;
// Framerate received from the source at the time of the adaptation.
int framerate_fps_;
// Degradation preference for the request.
Adaptation::StepType step_type_;
};
// Owner and modifier of the VideoSourceRestriction of this stream adaptor.
const std::unique_ptr<VideoSourceRestrictor> source_restrictor_;
// Decides the next adaptation target in DegradationPreference::BALANCED.
const BalancedDegradationSettings balanced_settings_;
// To guard against applying adaptations that have become invalidated, an
// Adaptation that is applied has to have a matching validation ID.
int adaptation_validation_id_;
// When deciding the next target up or down, different strategies are used
// depending on the DegradationPreference.
// https://w3c.github.io/mst-content-hint/#dom-rtcdegradationpreference
DegradationPreference degradation_preference_;
VideoStreamInputState input_state_;
// The input frame rate, resolution and adaptation direction of the last
// ApplyAdaptationTarget(). Used to avoid adapting twice if a recent
// adaptation has not had an effect on the input frame rate or resolution yet.
// TODO(hbos): Can we implement a more general "cooldown" mechanism of
// resources intead? If we already have adapted it seems like we should wait
// a while before adapting again, so that we are not acting on usage
// measurements that are made obsolete/unreliable by an "ongoing" adaptation.
absl::optional<AdaptationRequest> last_adaptation_request_;
};
} // namespace webrtc
#endif // CALL_ADAPTATION_VIDEO_STREAM_ADAPTER_H_