Move ContentVideoCaptureDeviceCore from src/content to src/media

content/browser/media/capture/animated_content_sampler.h

-// Copyright (c) 2015 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#ifndef CONTENT_BROWSER_MEDIA_CAPTURE_ANIMATED_CONTENT_SAMPLER_H_
-#define CONTENT_BROWSER_MEDIA_CAPTURE_ANIMATED_CONTENT_SAMPLER_H_
-
-#include <deque>
-
-#include "base/time/time.h"
-#include "content/common/content_export.h"
-#include "ui/gfx/geometry/rect.h"
-
-namespace content {
-
-// Analyzes a sequence of events to detect the presence of constant frame rate
-// animated content.  In the case where there are multiple regions of animated
-// content, AnimatedContentSampler will propose sampling the one having the
-// largest "smoothness" impact, according to human perception (e.g., a 24 FPS
-// video versus a 60 FPS busy spinner).
-//
-// In addition, AnimatedContentSampler will provide rewritten frame timestamps,
-// for downstream consumers, that are "truer" to the source content than to the
-// local presentation hardware.
-class CONTENT_EXPORT AnimatedContentSampler {
- public:
-  explicit AnimatedContentSampler(base::TimeDelta min_capture_period);
-  ~AnimatedContentSampler();
-
-  // Get/Set the target sampling period.  This is used to determine whether to
-  // subsample the frames of animated content.
-  base::TimeDelta target_sampling_period() const {
-    return target_sampling_period_;
-  }
-  void SetTargetSamplingPeriod(base::TimeDelta period);
-
-  // Examines the given presentation event metadata, along with recent history,
-  // to detect animated content, updating the state of this sampler.
-  // |damage_rect| is the region of a frame about to be drawn, while
-  // |event_time| refers to the frame's estimated presentation time.
-  void ConsiderPresentationEvent(const gfx::Rect& damage_rect,
-                                 base::TimeTicks event_time);
-
-  // Returns true if animated content has been detected and a decision has been
-  // made about whether to sample the last event.
-  bool HasProposal() const;
-
-  // Returns true if the last event considered should be sampled.
-  bool ShouldSample() const;
-
-  // Returns a frame timestamp to provide to consumers of the sampled frame.
-  // Only valid when ShouldSample() returns true.
-  base::TimeTicks frame_timestamp() const { return frame_timestamp_; }
-
-  // Returns the current sampling period.  This can be treated as the estimated
-  // duration of the frame to be sampled.  Only valid when HasProposal()
-  // returns true.
-  base::TimeDelta sampling_period() const { return sampling_period_; }
-
-  // Accessors to currently-detected animating region/period, for logging.
-  const gfx::Rect& detected_region() const { return detected_region_; }
-  base::TimeDelta detected_period() const { return detected_period_; }
-
-  // Records that a frame with the given |frame_timestamp| was sampled.  This
-  // method should be called when *any* sampling is taken, even if it was not
-  // proposed by AnimatedContentSampler.
-  void RecordSample(base::TimeTicks frame_timestamp);
-
- private:
-  friend class AnimatedContentSamplerTest;
-
-  // Data structure for efficient online analysis of recent event history.
-  struct Observation {
-    gfx::Rect damage_rect;
-    base::TimeTicks event_time;
-
-    Observation(const gfx::Rect& d, base::TimeTicks e)
-        : damage_rect(d), event_time(e) {}
-  };
-  typedef std::deque<Observation> ObservationFifo;
-
-  // Adds an observation to |observations_|, and prunes-out the old ones.
-  void AddObservation(const gfx::Rect& damage_rect, base::TimeTicks event_time);
-
-  // Returns the damage Rect that is responsible for the majority of the pixel
-  // damage in recent event history, if there is such a Rect.  If there isn't,
-  // this method could still return any Rect, so the caller must confirm the
-  // returned Rect really is responsible for the majority of pixel damage.
-  gfx::Rect ElectMajorityDamageRect() const;
-
-  // Analyzes the observations relative to the current |event_time| to detect
-  // stable animating content.  If detected, returns true and sets the output
-  // arguments to the region of the animating content and its mean frame
-  // duration.
-  bool AnalyzeObservations(base::TimeTicks event_time,
-                           gfx::Rect* rect,
-                           base::TimeDelta* period) const;
-
-  // Called by ConsiderPresentationEvent() when the current event is part of a
-  // detected animation, to update |frame_timestamp_|.
-  base::TimeTicks ComputeNextFrameTimestamp(base::TimeTicks event_time) const;
-
-  // When the animation frame rate is greater than the target sampling rate,
-  // this function determines an integer division of the animation frame rate
-  // that is closest to the target sampling rate.  Returns the inverse of that
-  // result (the period).  If the animation frame rate is slower or the same as
-  // the target sampling rate, this function just returns |animation_period|.
-  static base::TimeDelta ComputeSamplingPeriod(
-      base::TimeDelta animation_period,
-      base::TimeDelta target_sampling_period,
-      base::TimeDelta min_capture_period);
-
-  // The client expects frame timestamps to be at least this far apart.
-  const base::TimeDelta min_capture_period_;
-
-  // A recent history of observations in chronological order, maintained by
-  // AddObservation().
-  ObservationFifo observations_;
-
-  // The region of currently-detected animated content.  If empty, that means
-  // "not detected."
-  gfx::Rect detected_region_;
-
-  // The mean frame duration of currently-detected animated content.  If zero,
-  // that means "not detected."
-  base::TimeDelta detected_period_;
-
-  // Target period between sampled frames.  This can be changed by the client at
-  // any time (e.g., to sample high frame rate content at a lower rate).
-  base::TimeDelta target_sampling_period_;
-
-  // The sampling period computed during the last call to
-  // ConsiderPresentationEvent().
-  base::TimeDelta sampling_period_;
-
-  // Indicates whether the last event caused animated content to be detected and
-  // whether the current event should be sampled.
-  enum {
-    NOT_SAMPLING,
-    START_SAMPLING,
-    SHOULD_NOT_SAMPLE,
-    SHOULD_SAMPLE
-  } sampling_state_;
-
-  // A token bucket that is used to decide which subset of the frames containing
-  // the animated content should be sampled.  Here, the smallest discrete unit
-  // of time (one microsecond) equals one token; and, tokens are only taken from
-  // the bucket when at least a full sampling period's worth are present.
-  base::TimeDelta token_bucket_;
-
-  // The rewritten frame timestamp for the latest event.
-  base::TimeTicks frame_timestamp_;
-};
-
-}  // namespace content
-
-#endif  // CONTENT_BROWSER_MEDIA_CAPTURE_ANIMATED_CONTENT_SAMPLER_H_