cast: Support for low-latency interactive mode

media/capture/content/video_capture_oracle.cc

 // 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.
 
 #include "media/capture/content/video_capture_oracle.h"
 
 #include <algorithm>
 
 #include "base/format_macros.h"
 #include "base/numerics/safe_conversions.h"
@@ skipping 285 matching lines @@
           frame_number, delta.InMicroseconds(),
           100.0 * FractionFromExpectedFrameRate(delta, 30),
           100.0 * FractionFromExpectedFrameRate(delta, 25),
           100.0 * FractionFromExpectedFrameRate(delta, 24));
     }
   }
 
   return true;
 }
 
+bool VideoCaptureOracle::IsAnimationActive() const {
+  base::TimeDelta duration =
+      base::TimeTicks::Now() - last_time_animation_was_detected_;
+  return duration.InMicroseconds() < kDebouncingPeriodForAnimatedContentMicros;

[miu, 2015/12/01 21:15:27]

I don't think this does what you intended.  The kDebouncingPeriod is something
orthogonal.  It was meant to prevent unintended resolution increases as the
"capability" signals fluctuate.

The VCOracle only sets |last_time_animation_was_detected_| after the
AnimatedContentSampler detects animation, and that takes 1-2 seconds' worth of
events to trigger.  So, I think you can just use that.

Overall, I suggest an inline accessor for |last_time_animation_was_detected_|
and plumb this timestamp through to video_sender.cc.

[Irfan, 2015/12/02 22:32:44]

As discussed, this has the same intention. Will be moving the logic out though.

+}
+
 void VideoCaptureOracle::RecordConsumerFeedback(int frame_number,
                                                 double resource_utilization) {
   if (!auto_throttling_enabled_)
     return;
 
   if (!std::isfinite(resource_utilization)) {
     LOG(DFATAL) << "Non-finite utilization provided by consumer for frame #"
                 << frame_number << ": " << resource_utilization;
     return;
   }
@@ skipping 209 matching lines @@
   // Content is not animating, so permit an immediate increase in the capture
   // area.  This allows the system to quickly improve the quality of
   // non-animating content (frame drops are not much of a concern).
   VLOG(2) << "Proposing a "
           << (100.0 * (increased_area - current_area) / current_area)
           << "% increase in capture area for non-animating content.  :-)";
   return increased_area;
 }
 
 }  // namespace media