video_coding::PacketBuffer now group all H264 packets with the same timestamp into the same frame.

webrtc/modules/video_coding/packet_buffer.cc

 /*
  *  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 193 matching lines @@
     // If all packets of the frame is continuous, find the first packet of the
     // frame and create an RtpFrameObject.
     if (sequence_buffer_[index].frame_end) {
       size_t frame_size = 0;
       int max_nack_count = -1;
       uint16_t start_seq_num = seq_num;
 
       // Find the start index by searching backward until the packet with
       // the |frame_begin| flag is set.
       int start_index = index;
+
+      bool is_h264 = data_buffer_[start_index].codec == kVideoCodecH264;
+      int64_t frame_timestamp = data_buffer_[start_index].timestamp;
       while (true) {
         frame_size += data_buffer_[start_index].sizeBytes;
         max_nack_count =
             std::max(max_nack_count, data_buffer_[start_index].timesNacked);
         sequence_buffer_[start_index].frame_created = true;
 
-        if (sequence_buffer_[start_index].frame_begin)
+        if (!is_h264 && sequence_buffer_[start_index].frame_begin)
           break;
 
         start_index = start_index > 0 ? start_index - 1 : size_ - 1;
-        start_seq_num--;
+
+        if (is_h264 && start_index != static_cast<int>(index) &&

[stefan-webrtc, 2017/02/02 15:19:00]

Can we have a short comment on what this is trying to achieve? It's a bit hard
for a reader to interpret.

Is it something like "Beginning of an h.264 frame has been reached if the
timestamp changes and the begin bit has been found on the previous packet."? 
Why is that not true for all codecs? And do we know that the previous packet had
a begin bit?

[philipel, 2017/02/02 15:47:37]

Added a comment about it.

+            (!sequence_buffer_[start_index].used ||
+             data_buffer_[start_index].timestamp != frame_timestamp)) {
+          break;
+        }
+
+        --start_seq_num;
       }
 
       found_frames.emplace_back(
           new RtpFrameObject(this, start_seq_num, seq_num, frame_size,
                              max_nack_count, clock_->TimeInMilliseconds()));
     }
     ++seq_num;
     ++packets_tested;
   }
   return found_frames;
@@ skipping 55 matching lines @@
 int PacketBuffer::Release() const {
   int count = rtc::AtomicOps::Decrement(&ref_count_);
   if (!count) {
     delete this;
   }
   return count;
 }
 
 }  // namespace video_coding
 }  // namespace webrtc