Preliminary change for new rtc rendering algorithm

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 "base/compiler_specific.h"
 #include "base/time/time.h"
 #include "base/values.h"
@@ skipping 32 matching lines @@
     // frame-level resource utilization stats.  Use Get/SetTimeDelta() for this
     // key.
     FRAME_DURATION,
 
     // Represents either the fixed frame rate, or the maximum frame rate to
     // expect from a variable-rate source.  This value generally remains the
     // same for all frames in the same session.  Use Get/SetDouble() for this
     // key.
     FRAME_RATE,
 
+    // This field represents the local time at which either: 1) the frame was
+    // generated, if it was done so locally; or 2) the targeted play-out time
+    // of the frame, if it was generated from a remote source. This value is NOT
+    // a high-resolution timestamp, and so it should not be used as a
+    // presentation time; but, instead, it should be used for buffering playback
+    // and for A/V synchronization purposes.
+    // Use Get/SetTimeTicks() for this key.
+    REFERENCE_TIME,
+
     // A feedback signal that indicates the fraction of the tolerable maximum
     // amount of resources that were utilized to process this frame.  A producer
     // can check this value after-the-fact, usually via a VideoFrame destruction
     // observer, to determine whether the consumer can handle more or less data
     // volume, and achieve the right quality versus performance trade-off.
     //
     // Use Get/SetDouble() for this key.  Values are interpreted as follows:
     // Less than 0.0 is meaningless and should be ignored.  1.0 indicates a
     // maximum sustainable utilization.  Greater than 1.0 indicates the consumer
     // is likely to stall or drop frames if the data volume is not reduced.
@@ skipping 46 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_