Only advance |first_seq_num_| if packets are explicitly cleared from the PacketBuffer.

webrtc/modules/video_coding/packet_buffer.h

Index: webrtc/modules/video_coding/packet_buffer.h
diff --git a/webrtc/modules/video_coding/packet_buffer.h b/webrtc/modules/video_coding/packet_buffer.h
index 34a2d402bbbb24461a44dcd233264e86eef913bb..b9fb78207f297ae58b74be4174b741814bdbe5ea 100644
--- a/webrtc/modules/video_coding/packet_buffer.h
+++ b/webrtc/modules/video_coding/packet_buffer.h
@@ -94,7 +94,8 @@ class PacketBuffer {
   bool ExpandBufferSize() EXCLUSIVE_LOCKS_REQUIRED(crit_);
 
   // Test if all previous packets has arrived for the given sequence number.
-  bool IsContinuous(uint16_t seq_num) const EXCLUSIVE_LOCKS_REQUIRED(crit_);
+  bool PotentialNewFrame(uint16_t seq_num) const
+      EXCLUSIVE_LOCKS_REQUIRED(crit_);
 
   // Test if all packets of a frame has arrived, and if so, creates a frame.
   // May create multiple frames per invocation.
@@ -127,6 +128,9 @@ class PacketBuffer {
   // If the packet buffer has received its first packet.
   bool first_packet_received_ GUARDED_BY(crit_);
 
+  // If the buffer is cleared to a specific packet.
+  bool has_cleared_to_ GUARDED_BY(crit_);

[stefan-webrtc, 2016/10/18 17:57:23]

I have a hard time understanding this member. What specific packet has it
cleared to?

[philipel, 2016/10/19 08:34:54]

This variable is set to true when ClearTo() has been called. The reason I have
this variable is to be able to know if I should drop a packet because it's old
(we have cleared past it), or if I should accept it (due to reordering that
might occur at the start of the stream). See line 68 in packet_buffer.cc.

[danilchap, 2016/10/19 09:25:10]

may be name it something like
is_cleared_before_first_seq_num_ :
instead of describing past action, describe current state. (is instead of
has/was/had)
incorporate seq_num it is cleared to into name.
'before' as a notion of '<' since 'to' might mean '<='

+
   // Buffer that holds the inserted packets.
   std::vector<VCMPacket> data_buffer_ GUARDED_BY(crit_);