- 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

@@ -89,6 +89,9 @@ namespace MT
     optional<double> mLastJitter;
     ProbeStats<double> mJitter;
     double mMaxDelta = 0.0;
+    uint64_t mPrevRxTimestamp = 0;
+    uint64_t mPrevArrival = 0;
+    uint64_t mPrevTransit = 0;
 };
 
 class Statistics