Bug Fix: WebRTC Receiver Timestamp Jump Detection

webrtc/system_wrappers/source/timestamp_extrapolator.cc

 /*
  *  Copyright (c) 2011 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 67 matching lines @@
     }
 
     // Remove offset to prevent badly scaled matrices
     tMs -= _startMs;
 
     CheckForWrapArounds(ts90khz);
 
     int64_t unwrapped_ts90khz = static_cast<int64_t>(ts90khz) +
         _wrapArounds * ((static_cast<int64_t>(1) << 32) - 1);
 
-    if (_prevUnwrappedTimestamp >= 0 &&
-        unwrapped_ts90khz < _prevUnwrappedTimestamp)
-    {
-        // Drop reordered frames.
-        _rwLock->ReleaseLockExclusive();
-        return;
-    }
-
     if (_firstAfterReset)
     {
         // Make an initial guess of the offset,
         // should be almost correct since tMs - _startMs
         // should about zero at this time.
         _w[1] = -_w[0] * tMs;
         _firstTimestamp = unwrapped_ts90khz;
         _firstAfterReset = false;
     }
 
     double residual =
         (static_cast<double>(unwrapped_ts90khz) - _firstTimestamp) -
         static_cast<double>(tMs) * _w[0] - _w[1];
     if (DelayChangeDetection(residual) &&
         _packetCount >= _startUpFilterDelayInPackets)
     {
         // A sudden change of average network delay has been detected.
         // Force the filter to adjust its offset parameter by changing
         // the offset uncertainty. Don't do this during startup.
         _pP[1][1] = _pP11;
     }
+
+    if (_prevUnwrappedTimestamp >= 0 &&
+        unwrapped_ts90khz < _prevUnwrappedTimestamp)
+    {
+        // Drop reordered frames.
+        _rwLock->ReleaseLockExclusive();
+        return;
+    }
+
     //T = [t(k) 1]';
     //that = T'*w;
     //K = P*T/(lambda + T'*P*T);
     double K[2];
     K[0] = _pP[0][0] * tMs + _pP[0][1];
     K[1] = _pP[1][0] * tMs + _pP[1][1];
     double TPT = _lambda + tMs * K[0] + K[1];
     K[0] /= TPT;
     K[1] /= TPT;
     //w = w + K*(ts(k) - that);
@@ skipping 98 matching lines @@
     if (_detectorAccumulatorPos > _alarmThreshold || _detectorAccumulatorNeg < -_alarmThreshold)
     {
         // Alarm
         _detectorAccumulatorPos = _detectorAccumulatorNeg = 0;
         return true;
     }
     return false;
 }
 
 }