New FRAME_DURATION VideoFrameMetadata, with Cast Streaming use case.

content/browser/media/capture/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 CONTENT_BROWSER_MEDIA_CAPTURE_VIDEO_CAPTURE_ORACLE_H_
 #define CONTENT_BROWSER_MEDIA_CAPTURE_VIDEO_CAPTURE_ORACLE_H_
 
 #include "base/callback_forward.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/time/time.h"
@@ skipping 33 matching lines @@
 
   // Notify of the completion of a capture.  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, base::TimeTicks* frame_timestamp);
 
   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_;
+  }
+
  private:
   // Retrieve/Assign a frame timestamp by capture |frame_number|.
   base::TimeTicks GetFrameTimestamp(int frame_number) const;
   void SetFrameTimestamp(int frame_number, base::TimeTicks timestamp);
 
   // Incremented every time a paint or update event occurs.
   int 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 delivered frame.
   int last_delivered_frame_number_;
 
   // 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_;
 
   // 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];
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_MEDIA_CAPTURE_VIDEO_CAPTURE_ORACLE_H_