cast: Support for low-latency interactive mode

media/base/video_frame_metadata.h

 // Copyright 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 MEDIA_BASE_VIDEO_FRAME_METADATA_H_
 #define MEDIA_BASE_VIDEO_FRAME_METADATA_H_
 
+#include <string>
+
 #include "base/compiler_specific.h"
 #include "base/time/time.h"
 #include "base/values.h"
 #include "media/base/media_export.h"
 
 namespace media {
 
 class MEDIA_EXPORT VideoFrameMetadata {
  public:
   enum Key {
@@ skipping 52 matching lines @@
     // maximum sustainable utilization.  Greater than 1.0 indicates the consumer
     // is likely to stall or drop frames if the data volume is not reduced.
     //
     // Example: In a system that encodes and transmits video frames over the
     // network, this value can be used to indicate whether sufficient CPU
     // is available for encoding and/or sufficient bandwidth is available for
     // transmission over the network.  The maximum of the two utilization
     // measurements would be used as feedback.
     RESOURCE_UTILIZATION,
 
+    // This is a boolean that signals that the video capture engine detects
+    // interactive content. One possible optimization that this signal can help
+    // with is adjusting end-to-end latency based on whether the mode is turned

[miu, 2015/12/03 21:26:23]

For a bit more clarity for those unfamiliar with mirroring concepts:

s/with is adjusting/with is remoting content: adjusting/

and

s/based on whether the mode is turned on or off/down to help the user better
coordinate their actions/

[Irfan, 2015/12/04 22:45:37]

Done.

+    // on or off.
+    //
+    // Use Get/SetBoolean for this key.
+    INTERACTIVE_MODE,

[miu, 2015/12/03 21:26:23]

1. naming nit: How about INTERACTIVE_CONTENT?  (i.e., focus is on this
VideoFrame's media content, not an overall systemic "mode")

2. Please move this up so it's in alphabetical order.

[Irfan, 2015/12/04 22:45:37]

Done.

+
     NUM_KEYS
   };
 
   VideoFrameMetadata();
   ~VideoFrameMetadata();
 
   bool HasKey(Key key) const;
 
   void Clear() { dictionary_.Clear(); }
 
@@ skipping 28 matching lines @@
   const base::BinaryValue* GetBinaryValue(Key key) const;
 
   base::DictionaryValue dictionary_;
 
   DISALLOW_COPY_AND_ASSIGN(VideoFrameMetadata);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_BASE_VIDEO_FRAME_METADATA_H_