FrameBuffer::NextFrame now return pair<frame, reason>.

webrtc/modules/video_coding/frame_buffer2.h

 /*
  *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 18 matching lines @@
 class Clock;
 class VCMJitterEstimator;
 class VCMTiming;
 
 namespace video_coding {
 
 class FrameObject;
 
 class FrameBuffer {
  public:
+  enum ReturnReason {
+    kFrameFound,
+    kTimeout,
+    kStopped
+  };
+
   FrameBuffer(Clock* clock,
               VCMJitterEstimator* jitter_estimator,
               VCMTiming* timing);
 
   // Insert a frame into the frame buffer.
   void InsertFrame(std::unique_ptr<FrameObject> frame);
 
   // Get the next frame for decoding. Will return at latest after
-  // |max_wait_time_ms|, with either a managed FrameObject or an empty
-  // unique ptr if there is no available frame for decoding.
-  std::unique_ptr<FrameObject> NextFrame(int64_t max_wait_time_ms);
+  // |max_wait_time_ms|.
+  //  - If a frame is availiable within |max_wait_time_ms| it will return
+  //    {non-null unique ptr, kFrameFound}
+  //  - If no frame is available after |max_wait_time_ms| it will return
+  //    {null unique ptr, kTimeout}
+  //  - If the FrameBuffer is stopped then it will return
+  //    {null unique ptr, kStopped}
+  std::pair<std::unique_ptr<FrameObject>, ReturnReason>

[mflodman, 2016/09/02 12:05:57]

I'm not a big fan of returning a pair like this, wdyt of instead moving
FrameObject to the argument list?

[philipel, 2016/09/02 12:41:31]

The idea was to follow the stl style where pair<object, status> often is
returned, changed now to take an additional output parameter.

+      NextFrame(int64_t max_wait_time_ms);
 
   // Tells the FrameBuffer which protection mode that is in use. Affects
   // the frame timing.
   // TODO(philipel): Remove this when new timing calculations has been
   //                 implemented.
   void SetProtectionMode(VCMVideoProtection mode);
 
   // Start the frame buffer, has no effect if the frame buffer is started.
   // The frame buffer is started upon construction.
   void Start();
@@ skipping 33 matching lines @@
   bool stopped_ GUARDED_BY(crit_);
   VCMVideoProtection protection_mode_ GUARDED_BY(crit_);
 
   RTC_DISALLOW_IMPLICIT_CONSTRUCTORS(FrameBuffer);
 };
 
 }  // namespace video_coding
 }  // namespace webrtc
 
 #endif  // WEBRTC_MODULES_VIDEO_CODING_FRAME_BUFFER2_H_