Always unwrap VP9 TL0PicIdx forward if the frame is newer.

Bug: webrtc:12979
Change-Id: Idcc14f8f61b04f9eb194b55ffa40fb95319a881c
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/226463
Reviewed-by: Danil Chapovalov <[email protected]>
Reviewed-by: Ilya Nikolaevskiy <[email protected]>
Reviewed-by: Mirko Bonadei <[email protected]>
Commit-Queue: Philip Eliasson <[email protected]>
Cr-Commit-Position: refs/heads/master@{#34513}

Author: Philipel-WebRTC

modules/video_coding/rtp_vp9_ref_finder.cc

@@ -77,8 +77,21 @@ RtpVp9RefFinder::FrameDecision RtpVp9RefFinder::ManageFrameInternal(
   }
 
   GofInfo* info;
-  int64_t unwrapped_tl0 =
-      tl0_unwrapper_.Unwrap(codec_header.tl0_pic_idx & 0xFF);
+
+  // The VP9 `tl0_pic_idx` is 8 bits and therefor wraps often. In the case of
+  // packet loss the next received frame could have a `tl0_pic_idx` that looks
+  // older than the previously received frame. Always wrap forward if |frame| is
+  // newer in RTP packet sequence number order.
+  int64_t unwrapped_tl0;
+  auto tl0_it = gof_info_.rbegin();
+  if (tl0_it != gof_info_.rend() &&
+      AheadOf(frame->last_seq_num(), tl0_it->second.last_seq_num)) {
+    unwrapped_tl0 =
+        tl0_unwrapper_.UnwrapForward(codec_header.tl0_pic_idx & 0xFF);
+  } else {
+    unwrapped_tl0 = tl0_unwrapper_.Unwrap(codec_header.tl0_pic_idx & 0xFF);
+  }
+
   if (codec_header.ss_data_available) {
     if (codec_header.temporal_idx != 0) {
       RTC_LOG(LS_WARNING) << "Received scalability structure on a non base "
@@ -104,9 +117,9 @@ RtpVp9RefFinder::FrameDecision RtpVp9RefFinder::ManageFrameInternal(
       current_ss_idx_ = Add<kMaxGofSaved>(current_ss_idx_, 1);
       scalability_structures_[current_ss_idx_] = gof;
       scalability_structures_[current_ss_idx_].pid_start = frame->Id();
-      gof_info_.emplace(
-          unwrapped_tl0,
-          GofInfo(&scalability_structures_[current_ss_idx_], frame->Id()));
+      gof_info_.emplace(unwrapped_tl0,
+                        GofInfo(&scalability_structures_[current_ss_idx_],
+                                frame->Id(), frame->last_seq_num()));
     }
 
     const auto gof_info_it = gof_info_.find(unwrapped_tl0);
@@ -147,7 +160,8 @@ RtpVp9RefFinder::FrameDecision RtpVp9RefFinder::ManageFrameInternal(
     if (codec_header.temporal_idx == 0) {
       gof_info_it = gof_info_
                         .emplace(unwrapped_tl0,
-                                 GofInfo(gof_info_it->second.gof, frame->Id()))
+                                 GofInfo(gof_info_it->second.gof, frame->Id(),
+                                         frame->last_seq_num()))
                         .first;
     }
 

modules/video_coding/rtp_vp9_ref_finder.h

@@ -42,10 +42,13 @@ class RtpVp9RefFinder {
   enum FrameDecision { kStash, kHandOff, kDrop };
 
   struct GofInfo {
-    GofInfo(GofInfoVP9* gof, uint16_t last_picture_id)
-        : gof(gof), last_picture_id(last_picture_id) {}
+    GofInfo(GofInfoVP9* gof, uint16_t last_picture_id, uint16_t last_seq_num)
+        : gof(gof),
+          last_picture_id(last_picture_id),
+          last_seq_num(last_seq_num) {}
     GofInfoVP9* gof;
     uint16_t last_picture_id;
+    uint16_t last_seq_num;
   };
 
   FrameDecision ManageFrameInternal(RtpFrameObject* frame);

modules/video_coding/rtp_vp9_ref_finder_unittest.cc

@@ -23,6 +23,7 @@ using ::testing::Matches;
 using ::testing::MatchResultListener;
 using ::testing::Pointee;
 using ::testing::Property;
+using ::testing::SizeIs;
 using ::testing::UnorderedElementsAreArray;
 
 namespace webrtc {
@@ -661,6 +662,24 @@ TEST_F(RtpVp9RefFinderTest, GofTl0Jump) {
   Insert(Frame().Pid(1).SidAndTid(0, 0).Tl0(0).Gof(&ss));
 }
 
+TEST_F(RtpVp9RefFinderTest, DontDiscardNewerFramesWithWrappedTl0) {
+  GofInfoVP9 ss;
+  ss.SetGofInfoVP9(kTemporalStructureMode1);
+
+  Insert(
+      Frame().Pid(0).SidAndTid(0, 0).Tl0(0).SeqNum(0, 0).AsKeyFrame().Gof(&ss));
+  // ... 254 frames are lost ...
+  Insert(Frame()
+             .Pid(255)
+             .SidAndTid(0, 0)
+             .Tl0(255)
+             .SeqNum(255, 255)
+             .AsKeyFrame()
+             .Gof(&ss));
+
+  EXPECT_THAT(frames_, SizeIs(2));
+}
+
 TEST_F(RtpVp9RefFinderTest, GofTidTooHigh) {
   const int kMaxTemporalLayers = 5;
   GofInfoVP9 ss;