Request keyframe if too many packets are missing and NACK is disabled.

webrtc/modules/video_coding/main/source/jitter_buffer.cc

Index: webrtc/modules/video_coding/main/source/jitter_buffer.cc
diff --git a/webrtc/modules/video_coding/main/source/jitter_buffer.cc b/webrtc/modules/video_coding/main/source/jitter_buffer.cc
index 9156cc1a61dba45624bda8c73da4886fce71b242..07bed230aa7b763b81a43cb6aefc492f79ac4014 100644
--- a/webrtc/modules/video_coding/main/source/jitter_buffer.cc
+++ b/webrtc/modules/video_coding/main/source/jitter_buffer.cc
@@ -940,9 +940,6 @@ VCMFrameBuffer* VCMJitterBuffer::NextFrame() const {
 }
 
 bool VCMJitterBuffer::UpdateNackList(uint16_t sequence_number) {
-  if (nack_mode_ == kNoNack) {
-    return true;
-  }
   // Make sure we don't add packets which are already too old to be decoded.
   if (!last_decoded_state_.in_initial_state()) {
     latest_received_sequence_number_ = LatestSequenceNumber(
@@ -951,6 +948,10 @@ bool VCMJitterBuffer::UpdateNackList(uint16_t sequence_number) {
   }
   if (IsNewerSequenceNumber(sequence_number,
                             latest_received_sequence_number_)) {
+    if (nack_mode_ == kNoNack) {
+      // Packets missing but NACK disabled, request key frame.

[pbos-webrtc, 2015/06/26 05:01:02]

Should we request a keyframe even though the sequence is decodable? That might
make sense, since quality will start to deteriorate.

Also should this be called UpdateNackList if it's not related to NACK? Should
this check be plugged in elsewhere, or method renamed?

[joachim, 2015/06/26 07:46:01]

I'm not sure how to check if the sequence is decodable at that point. Isn't that
something only the codec knows?
I renamed the method to "CoverSequenceUpTo" and updated the comment in the
header file.

+      return false;
+    }
     // Push any missing sequence numbers to the NACK list.
     for (uint16_t i = latest_received_sequence_number_ + 1;
          IsNewerSequenceNumber(sequence_number, i); ++i) {
@@ -967,7 +968,7 @@ bool VCMJitterBuffer::UpdateNackList(uint16_t sequence_number) {
       LOG(LS_WARNING) << "Requesting key frame due to missing too old packets";
       return false;
     }
-  } else {
+  } else if (nack_mode_ != kNoNack) {
     missing_sequence_numbers_.erase(sequence_number);
     TRACE_EVENT_INSTANT1(TRACE_DISABLED_BY_DEFAULT("webrtc_rtp"), "RemoveNack",
                          "seqnum", sequence_number);