If present, only use picture ids to identify missing frames.

This is necessary in some scenarios to avoid false non-zero loss reports when doing stream thinning.

BUG=

Review URL: https://webrtc-codereview.appspot.com/793008

git-svn-id: http://webrtc.googlecode.com/svn/trunk@2784 4adac7df-926f-26a2-2b94-8c16560cd09d

src/modules/video_coding/main/source/decoding_state.cc

@@ -127,10 +127,11 @@ void VCMDecodingState::UpdateSyncState(const VCMFrameBuffer* frame) {
     // Verify that we are still in sync.
     // Sync will be broken if continuity is true for layers but not for the
     // other methods (PictureId and SeqNum).
-    if (!ContinuousPictureId(frame->PictureId()) &&
-        !ContinuousSeqNum(static_cast<uint16_t>(frame->GetLowSeqNum()))) {
-      // Non-layered methods have failed.
-      full_sync_ = false;
+    if (UsingPictureId(frame)) {
+      full_sync_ = ContinuousPictureId(frame->PictureId());
+    } else {
+      full_sync_ = ContinuousSeqNum(static_cast<uint16_t>(
+          frame->GetLowSeqNum()));
     }
   }
 }
@@ -152,17 +153,16 @@ bool VCMDecodingState::ContinuousFrame(const VCMFrameBuffer* frame) const {
     // continuity if sync can be restored by this frame.
     if (!full_sync_ && !frame->LayerSync())
       return false;
-    else if (!ContinuousPictureId(frame->PictureId()))
+    else if (UsingPictureId(frame)) {
+      return ContinuousPictureId(frame->PictureId());
+    } else {
       return ContinuousSeqNum(static_cast<uint16_t>(frame->GetLowSeqNum()));
+    }
   }
   return true;
 }
 
 bool VCMDecodingState::ContinuousPictureId(int picture_id) const {
-  // First, check if applicable.
-  if (picture_id == kNoPictureId || picture_id_ == kNoPictureId)
-    return false;
-
   int next_picture_id = picture_id_ + 1;
   if (picture_id < picture_id_) {
     // Wrap
@@ -199,4 +199,8 @@ bool VCMDecodingState::ContinuousLayer(int temporal_id,
   return (static_cast<uint8_t>(tl0_pic_id_ + 1) == tl0_pic_id);
 }
 
+bool VCMDecodingState::UsingPictureId(const VCMFrameBuffer* frame) const {
+  return (frame->PictureId() != kNoPictureId && picture_id_ != kNoPictureId);
+}
+
 }  // namespace webrtc

src/modules/video_coding/main/source/decoding_state.h

@@ -52,6 +52,7 @@ class VCMDecodingState {
   bool ContinuousPictureId(int picture_id) const;
   bool ContinuousSeqNum(uint16_t seq_num) const;
   bool ContinuousLayer(int temporal_id, int tl0_pic_id) const;
+  bool UsingPictureId(const VCMFrameBuffer* frame) const;
 
   // Keep state of last decoded frame.
   // TODO(mikhal/stefan): create designated classes to handle these types.

src/modules/video_coding/main/source/decoding_state_unittest.cc

@@ -405,6 +405,38 @@ TEST(TestDecodingState, MultiLayerBehavior) {
   delete packet;
 }
 
+TEST(TestDecodingState, DiscontinuousPicIdContinuousSeqNum) {
+  VCMDecodingState dec_state;
+  VCMFrameBuffer frame;
+  VCMPacket packet;
+  frame.Reset();
+  frame.SetState(kStateEmpty);
+  packet.frameType = kVideoFrameKey;
+  packet.codecSpecificHeader.codec = kRTPVideoVP8;
+  packet.timestamp = 0;
+  packet.seqNum = 0;
+  packet.codecSpecificHeader.codecHeader.VP8.tl0PicIdx = 0;
+  packet.codecSpecificHeader.codecHeader.VP8.temporalIdx = 0;
+  packet.codecSpecificHeader.codecHeader.VP8.pictureId = 0;
+  frame.InsertPacket(packet, 0, false, 0);
+  dec_state.SetState(&frame);
+  EXPECT_TRUE(dec_state.full_sync());
+
+  // Continuous sequence number but discontinuous picture id. This implies a
+  // a loss and we have to fall back to only decoding the base layer.
+  frame.Reset();
+  frame.SetState(kStateEmpty);
+  packet.frameType = kVideoFrameDelta;
+  packet.timestamp += 3000;
+  ++packet.seqNum;
+  packet.codecSpecificHeader.codecHeader.VP8.temporalIdx = 1;
+  packet.codecSpecificHeader.codecHeader.VP8.pictureId = 2;
+  frame.InsertPacket(packet, 0, false, 0);
+  EXPECT_FALSE(dec_state.ContinuousFrame(&frame));
+  dec_state.SetState(&frame);
+  EXPECT_FALSE(dec_state.full_sync());
+}
+
 TEST(TestDecodingState, OldInput) {
   VCMDecodingState dec_state;
   // Identify packets belonging to old frames/packets.