- make jitter calculation closer to RFC

src/engine/media/MT_Statistics.cpp

@@ -9,7 +9,38 @@ using namespace MT;
 
 void JitterStatistics::process(jrtplib::RTPPacket* packet, int rate)
 {
+    uint32_t      arrival = 0;
+    int           d = 0;
+    uint32_t      transit = 0;
+
+    uint64_t    current_time = TimeHelper::getTimestamp();
+    int         interarrival_time_ms = current_time - mPrevRxTimestamp;
+
+    // get the 'arrival time' of this packet as measured in 'timestamp units' and offset
+    //  to match the timestamp range in this stream
+    arrival = interarrival_time_ms * (rate / 1000);
+
+    if (mPrevArrival == 0)
+        arrival = packet->GetTimestamp();
+    else
+        arrival += mPrevArrival;;
+
+    mPrevArrival = packet->GetTimestamp();
+
+    transit = arrival - packet->GetTimestamp();
     jrtplib::RTPTime receiveTime = packet->GetReceiveTime();
+
+    d = transit - mPrevTransit;
+    mPrevTransit = transit;
+    if (d < 0)
+        d = -d;
+    mJitter += (1.0/16.0) * ((double)d - mJitter);
+
+    mPrevRxTimestamp = current_time;
+    if (mMaxJitter < mJitter)
+        mMaxJitter = mJitter;
+
+
     uint32_t timestamp = packet->GetTimestamp();
 
     if (!mLastJitter.is_initialized())
@@ -20,7 +51,14 @@ void JitterStatistics::process(jrtplib::RTPPacket* packet, int rate)
     }
     else
     {
-    double delta = (receiveTime.GetDouble() - mReceiveTime.GetDouble()) - double(timestamp - mReceiveTimestamp) / rate;
+        double receiveDelta = receiveTime.GetDouble() - mReceiveTime.GetDouble();
+        double timestampDelta = double(timestamp - mReceiveTimestamp);
+
+        if (timestampDelta == 0.0)
+            // Skip current packet silently. Most probably it is error in RTP stream like duplicated packet.
+            return;
+
+        double delta = receiveDelta / timestampDelta;
         if (fabs(delta) > mMaxDelta)
             mMaxDelta = fabs(delta);
 

src/engine/media/MT_Statistics.h

@@ -15,9 +15,9 @@ using std::experimental::optional;
 
 namespace MT
 {
-  template<typename T>
+template<typename T>
-  struct Average
+struct Average
-  {
+{
     int mCount = 0;
     T mSum = 0;
     T getAverage() const
@@ -32,11 +32,11 @@ namespace MT
         mCount++;
         mSum += value;
     }
-  };
+};
 
-  template<typename T, int minimum = 100000, int maximum = 0>
+template<typename T, int minimum = 100000, int maximum = 0>
-  struct ProbeStats
+struct ProbeStats
-  {
+{
     T mMin = minimum;
     T mMax = maximum;
     Average<T> mAverage;
@@ -64,36 +64,39 @@ namespace MT
         else
             return 0;
     }
-  };
+};
 
 
-  template<typename T>
+template<typename T>
-  struct StreamStats
+struct StreamStats
-  {
+{
     T mChunk;
     T mTotal;
-  };
+};
 
 
-  class JitterStatistics
+class JitterStatistics
-  {
+{
-  public:
+public:
     void process(jrtplib::RTPPacket* packet, int samplerate);
     ProbeStats<double> get() const  { return mJitter; }
     double getMaxDelta() const      { return mMaxDelta; }
 
-  protected:
+protected:
     // Jitter calculation
     jrtplib::RTPTime mReceiveTime = jrtplib::RTPTime(0,0);
     uint32_t mReceiveTimestamp = 0;
     optional<double> mLastJitter;
     ProbeStats<double> mJitter;
     double mMaxDelta = 0.0;
-  };
+    uint64_t mPrevRxTimestamp = 0;
+    uint64_t mPrevArrival = 0;
+    uint64_t mPrevTransit = 0;
+};
 
-  class Statistics
+class Statistics
-  {
+{
-  public:
+public:
     int       mReceived,        // Received traffic in bytes
     mSent,            // Sent traffic in bytes
     mReceivedRtp,     // Number of received rtp packets
@@ -136,13 +139,13 @@ namespace MT
     Statistics& operator -= (const Statistics& src);
 
     float mNetworkMos = 0.0;
-  #if defined(USE_PVQA_LIBRARY) && !defined(PVQA_SERVER)
+#if defined(USE_PVQA_LIBRARY) && !defined(PVQA_SERVER)
     float mPvqaMos = 0.0;
     std::string mPvqaReport;
-  #endif
+#endif
 
     std::string toShortString() const;
-  };
+};
 
 } // end of namespace MT