[WIP] Move media/capture to device/capture

media/capture/content/video_capture_oracle.h

-// Copyright (c) 2013 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 MEDIA_CAPTURE_CONTENT_VIDEO_CAPTURE_ORACLE_H_
-#define MEDIA_CAPTURE_CONTENT_VIDEO_CAPTURE_ORACLE_H_
-
-#include "base/callback_forward.h"
-#include "base/time/time.h"
-#include "media/capture/capture_export.h"
-#include "media/capture/content/animated_content_sampler.h"
-#include "media/capture/content/capture_resolution_chooser.h"
-#include "media/capture/content/feedback_signal_accumulator.h"
-#include "media/capture/content/smooth_event_sampler.h"
-#include "ui/gfx/geometry/rect.h"
-
-namespace media {
-
-// VideoCaptureOracle manages the producer-side throttling of captured frames
-// from a video capture device.  It is informed of every update by the device;
-// this empowers it to look into the future and decide if a particular frame
-// ought to be captured in order to achieve its target frame rate.
-class CAPTURE_EXPORT VideoCaptureOracle {
- public:
-  enum Event {
-    kCompositorUpdate,
-    kActiveRefreshRequest,
-    kPassiveRefreshRequest,
-    kMouseCursorUpdate,
-    kNumEvents,
-  };
-
-  VideoCaptureOracle(base::TimeDelta min_capture_period,
-                     const gfx::Size& max_frame_size,
-                     media::ResolutionChangePolicy resolution_change_policy,
-                     bool enable_auto_throttling);
-
-  virtual ~VideoCaptureOracle();
-
-  // Sets the source content size.  This may not have an immediate effect on the
-  // proposed capture size, as the oracle will prevent too-frequent changes from
-  // occurring.
-  void SetSourceSize(const gfx::Size& source_size);
-
-  // Record a event of type |event|, and decide whether the caller should do a
-  // frame capture.  |damage_rect| is the region of a frame about to be drawn,
-  // and may be an empty Rect, if this is not known.  If the caller accepts the
-  // oracle's proposal, it should call RecordCapture() to indicate this.
-  bool ObserveEventAndDecideCapture(Event event,
-                                    const gfx::Rect& damage_rect,
-                                    base::TimeTicks event_time);
-
-  // Record and update internal state based on whether the frame capture will be
-  // started.  |pool_utilization| is a value in the range 0.0 to 1.0 to indicate
-  // the current buffer pool utilization relative to a sustainable maximum (not
-  // the absolute maximum).  This method should only be called if the last call
-  // to ObserveEventAndDecideCapture() returned true.  The first method returns
-  // the |frame_number| to be used with CompleteCapture().
-  int RecordCapture(double pool_utilization);
-  void RecordWillNotCapture(double pool_utilization);
-
-  // Notify of the completion of a capture, and whether it was successful.
-  // Returns true iff the captured frame should be delivered.  |frame_timestamp|
-  // is set to the timestamp that should be provided to the consumer of the
-  // frame.
-  bool CompleteCapture(int frame_number,
-                       bool capture_was_successful,
-                       base::TimeTicks* frame_timestamp);
-
-  // Record the resource utilization feedback for a frame that was processed by
-  // the consumer.  This allows the oracle to reduce/increase future data volume
-  // if the consumer is overloaded/under-utilized.  |resource_utilization| is a
-  // value in the range 0.0 to 1.0 to indicate the current consumer resource
-  // utilization relative to a sustainable maximum (not the absolute maximum).
-  // This method should only be called for frames where CompleteCapture()
-  // returned true.
-  void RecordConsumerFeedback(int frame_number, double resource_utilization);
-
-  base::TimeDelta min_capture_period() const {
-    return smoothing_sampler_.min_capture_period();
-  }
-
-  // Returns the oracle's estimate of the duration of the next frame.  This
-  // should be called just after ObserveEventAndDecideCapture(), and will only
-  // be non-zero if the call returned true.
-  base::TimeDelta estimated_frame_duration() const {
-    return duration_of_next_frame_;
-  }
-
-  // Returns the capture frame size the client should use.  This is updated by
-  // calls to ObserveEventAndDecideCapture().  The oracle prevents too-frequent
-  // changes to the capture size, to avoid stressing the end-to-end pipeline.
-  gfx::Size capture_size() const { return capture_size_; }
-
-  // Returns the oracle's estimate of the last time animation was detected.
-  base::TimeTicks last_time_animation_was_detected() const {
-    return last_time_animation_was_detected_;
-  }
-
-  // Returns a NUL-terminated string containing a short, human-readable form of
-  // |event|.
-  static const char* EventAsString(Event event);
-
- private:
-  // Retrieve/Assign a frame timestamp by capture |frame_number|.  Only valid
-  // when IsFrameInRecentHistory(frame_number) returns true.
-  base::TimeTicks GetFrameTimestamp(int frame_number) const;
-  void SetFrameTimestamp(int frame_number, base::TimeTicks timestamp);
-
-  // Returns true if the frame timestamp ring-buffer currently includes a
-  // slot for the given |frame_number|.
-  bool IsFrameInRecentHistory(int frame_number) const;
-
-  // Queries the ResolutionChooser to update |capture_size_|, and resets all the
-  // FeedbackSignalAccumulator members to stable-state starting values.  The
-  // accumulators are reset such that they can only apply feedback updates for
-  // future frames (those with a timestamp after |last_frame_time|).
-  void CommitCaptureSizeAndReset(base::TimeTicks last_frame_time);
-
-  // Called after a capture or no-capture decision was recorded.  This analyzes
-  // current state and may result in a future change to the capture frame size.
-  void AnalyzeAndAdjust(base::TimeTicks analyze_time);
-
-  // Analyzes current feedback signal accumulators for an indication that the
-  // capture size should be decreased.  Returns either a decreased area, or -1
-  // if no decrease should be made.
-  int AnalyzeForDecreasedArea(base::TimeTicks analyze_time);
-
-  // Analyzes current feedback signal accumulators for an indication that the
-  // the system has had excellent long-term performance and the capture size
-  // should be increased to improve quality.  Returns either an increased area,
-  // or -1 if no increase should be made.
-  int AnalyzeForIncreasedArea(base::TimeTicks analyze_time);
-
-  // Set to false to prevent the oracle from automatically adjusting the capture
-  // size in response to end-to-end utilization.
-  const bool auto_throttling_enabled_;
-
-  // Incremented every time a paint or update event occurs.
-  int next_frame_number_;
-
-  // Stores the last |event_time| from the last observation/decision.  Used to
-  // sanity-check that event times are monotonically non-decreasing.
-  base::TimeTicks last_event_time_[kNumEvents];
-
-  // Updated by the last call to ObserveEventAndDecideCapture() with the
-  // estimated duration of the next frame to sample.  This is zero if the method
-  // returned false.
-  base::TimeDelta duration_of_next_frame_;
-
-  // Stores the frame number from the last successfully delivered frame.
-  int last_successfully_delivered_frame_number_;
-
-  // Stores the number of pending frame captures.
-  int num_frames_pending_;
-
-  // These track present/paint history and propose whether to sample each event
-  // for capture.  |smoothing_sampler_| uses a "works for all" heuristic, while
-  // |content_sampler_| specifically detects animated content (e.g., video
-  // playback) and decides which events to sample to "lock into" that content.
-  SmoothEventSampler smoothing_sampler_;
-  AnimatedContentSampler content_sampler_;
-
-  // Determines video capture frame sizes.
-  CaptureResolutionChooser resolution_chooser_;
-
-  // The timestamp of the frame just before the last call to SetSourceSize().
-  base::TimeTicks source_size_change_time_;
-
-  // The current capture size.  |resolution_chooser_| may hold an updated value
-  // because the oracle prevents this size from changing too frequently.  This
-  // avoids over-stressing consumers (e.g., when a window is being activly
-  // drag-resized) and allowing the end-to-end system time to stabilize.
-  gfx::Size capture_size_;
-
-  // Recent history of frame timestamps proposed by VideoCaptureOracle.  This is
-  // a ring-buffer, and should only be accessed by the Get/SetFrameTimestamp()
-  // methods.
-  enum { kMaxFrameTimestamps = 16 };
-  base::TimeTicks frame_timestamps_[kMaxFrameTimestamps];
-
-  // Recent average buffer pool utilization for capture.
-  FeedbackSignalAccumulator<base::TimeTicks> buffer_pool_utilization_;
-
-  // Estimated maximum frame area that currently can be handled by the consumer,
-  // in number of pixels per frame.  This is used to adjust the capture size up
-  // or down to a data volume the consumer can handle.  Note that some consumers
-  // do not provide feedback, and the analysis logic should account for that.
-  FeedbackSignalAccumulator<base::TimeTicks> estimated_capable_area_;
-
-  // The time of the first analysis which concluded the end-to-end system was
-  // under-utilized.  If null, the system is not currently under-utilized.  This
-  // is used to determine when a proving period has elapsed that justifies an
-  // increase in capture size.
-  base::TimeTicks start_time_of_underutilization_;
-
-  // The timestamp of the frame where |content_sampler_| last detected
-  // animation.  This determines whether capture size increases will be
-  // aggressive (because content is not animating).
-  base::TimeTicks last_time_animation_was_detected_;
-};
-
-}  // namespace media
-
-#endif  // MEDIA_CAPTURE_CONTENT_VIDEO_CAPTURE_ORACLE_H_