Don't recalculate Tl0PicIdx when the VP9 frame has no Tl0PicIdx.

webrtc/modules/video_coding/rtp_frame_reference_finder.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 658 matching lines @@
     // frames that was inserted into the FrameBuffer.
     vp9_fix_pid_offset_ = ForwardDiff<uint16_t, kPicIdLength>(
         *picture_id, vp9_fix_last_picture_id_);
     vp9_fix_pid_offset_ += kMaxPidDiff;
 
     fixed_pid = Add<kPicIdLength>(*picture_id, vp9_fix_pid_offset_);
     vp9_fix_last_picture_id_ = fixed_pid;
     vp9_fix_jump_timestamp_ = frame.timestamp;
     gof_info_.clear();
 
-    vp9_fix_tl0_pic_idx_offset_ =
-        ForwardDiff<uint8_t>(*tl0_pic_idx, vp9_fix_last_tl0_pic_idx_);
-    vp9_fix_tl0_pic_idx_offset_ += kMaxGofSaved;
-    fixed_tl0 = Add<kTl0PicIdLength>(*tl0_pic_idx, vp9_fix_tl0_pic_idx_offset_);
-    vp9_fix_last_tl0_pic_idx_ = fixed_tl0;
+    if (fixed_tl0 != kNoTl0PicIdx) {
+      vp9_fix_tl0_pic_idx_offset_ =
+          ForwardDiff<uint8_t>(*tl0_pic_idx, vp9_fix_last_tl0_pic_idx_);
+      vp9_fix_tl0_pic_idx_offset_ += kMaxGofSaved;
+      fixed_tl0 =
+          Add<kTl0PicIdLength>(*tl0_pic_idx, vp9_fix_tl0_pic_idx_offset_);
+      vp9_fix_last_tl0_pic_idx_ = fixed_tl0;
+    }
   }
 
   // Update |vp9_fix_last_picture_id_| with the most recent picture id.
   if (AheadOf<uint16_t, kPicIdLength>(fixed_pid, vp9_fix_last_picture_id_))
     vp9_fix_last_picture_id_ = fixed_pid;
 
   *picture_id = fixed_pid;
   *tl0_pic_idx = fixed_tl0;
 
   return false;
@@ skipping 54 matching lines @@
     if (!gof_info_.empty() &&
         AheadOf<uint8_t>(gof_info_.begin()->first, fixed_tl0)) {
       return true;
     }
   }
   return false;
 }
 
 }  // namespace video_coding
 }  // namespace webrtc