[core] New moving average value for sent/recv rates over last second (#3009)

* [core] Average values for sent/recv bitrate are now over last second.

* [core] Adding packet header size in average measure

* [core] Removing inheritance and fixing issue in rate compute

Author: npanhaleux

srtcore/buffer_tools.cpp

@@ -273,5 +273,65 @@ int CSndRateEstimator::incSampleIdx(int val, int inc) const
     return val;
 }
 
+CMovingRateEstimator::CMovingRateEstimator()
+    : m_tsFirstSampleTime(sync::steady_clock::now())
+    , m_iCurSampleIdx(0)
+    , m_iRateBps(0)
+    , m_Samples(NUM_PERIODS)
+{
+    resetRate(0, NUM_PERIODS);
 }
 
+void CMovingRateEstimator::addSample(int pkts, double bytes)
+{
+    const time_point now             = steady_clock::now();
+    const int        iSampleDeltaIdx = int(count_milliseconds(now - m_tsLastSlotTimestamp) / SAMPLE_DURATION_MS);
+
+    if (iSampleDeltaIdx == 0)
+    {
+        m_Samples[m_iCurSampleIdx].m_iBytesCount += bytes;
+        m_Samples[m_iCurSampleIdx].m_iPktsCount += pkts;
+    }
+    else
+    {
+        if ((m_iCurSampleIdx + iSampleDeltaIdx) < NUM_PERIODS)
+            resetRate(m_iCurSampleIdx + 1, m_iCurSampleIdx + iSampleDeltaIdx);
+        else
+        {
+            int loopbackDiff = m_iCurSampleIdx + iSampleDeltaIdx - NUM_PERIODS;
+            resetRate(m_iCurSampleIdx + 1, NUM_PERIODS);
+            resetRate(0, loopbackDiff);
+        }
+
+        m_iCurSampleIdx                          = ((m_iCurSampleIdx + iSampleDeltaIdx) % NUM_PERIODS);
+        m_Samples[m_iCurSampleIdx].m_iBytesCount = bytes;
+        m_Samples[m_iCurSampleIdx].m_iPktsCount  = pkts;
+
+        m_tsLastSlotTimestamp += milliseconds_from(SAMPLE_DURATION_MS * iSampleDeltaIdx);
+
+        computeAverageValue();
+    }
+}
+
+void CMovingRateEstimator::resetRate(int from, int to)
+{
+    for (int i = max(0, from); i < min(int(NUM_PERIODS), to); i++)
+        m_Samples[i].reset();
+}
+
+void CMovingRateEstimator::computeAverageValue()
+{
+    const time_point now           = steady_clock::now();
+    const int        startDelta    = count_milliseconds(now - m_tsFirstSampleTime);
+    const bool       isFirstPeriod = startDelta < (SAMPLE_DURATION_MS * NUM_PERIODS);
+    int              newRateBps    = 0;
+
+    for (int i = 0; i < NUM_PERIODS; i++)
+        newRateBps += (m_Samples[i].m_iBytesCount + (CPacket::HDR_SIZE * m_Samples[i].m_iPktsCount));
+
+    if (isFirstPeriod)
+        newRateBps = newRateBps * SAMPLE_DURATION_MS * NUM_PERIODS / max(1, startDelta);
+
+    m_iRateBps = newRateBps;
+}
+} // namespace srt

srtcore/buffer_tools.h

@@ -192,10 +192,87 @@ class CSndRateEstimator
 
     Sample m_Samples[NUM_PERIODS];
 
-    time_point m_tsFirstSampleTime; //< Start time of the first sample.
+    time_point m_tsFirstSampleTime; //< Start time of the first sameple.
     int        m_iFirstSampleIdx;   //< Index of the first sample.
     int        m_iCurSampleIdx;     //< Index of the current sample being collected.
-    int        m_iRateBps;          //< Rate in Bytes/sec.
+    int        m_iRateBps;          // Input Rate in Bytes/sec
+};
+
+class CMovingRateEstimator
+{
+    typedef sync::steady_clock::time_point time_point;
+
+public:
+    CMovingRateEstimator();
+
+    /// Add sample.
+    /// @param [in] pkts   number of packets in the sample.
+    /// @param [in] bytes  number of payload bytes in the sample.
+    void addSample(int pkts = 0, double bytes = 0);
+
+    /// Clean the mobile measures table to reset average value.
+    void resetRate() { resetRate(0, NUM_PERIODS); };
+
+    /// Retrieve estimated bitrate in bytes per second with 16-byte packet header.
+    int getRate() const { return m_iRateBps; }
+
+private:
+    // We would like responsiveness (accuracy) of rate estimation higher than 100 ms
+    // (ideally around 50 ms) for network adaptive algorithms.
+    static const int NUM_PERIODS        = 100; // To get 1s of values
+    static const int SAMPLE_DURATION_MS = 10;  // 10 ms
+    time_point       m_tsFirstSampleTime;      //< Start time of the first sample.
+    time_point       m_tsLastSlotTimestamp;    // Used to compute the delta between 2 calls
+    int              m_iCurSampleIdx;          //< Index of the current sample being collected.
+    int              m_iRateBps;               //< Rate in Bytes/sec.
+
+    struct Sample
+    {
+        int m_iPktsCount;  // number of payload packets
+        int m_iBytesCount; // number of payload bytes
+
+        void reset()
+        {
+            m_iPktsCount  = 0;
+            m_iBytesCount = 0;
+        }
+
+        Sample()
+            : m_iPktsCount(0)
+            , m_iBytesCount(0)
+        {
+        }
+
+        Sample(int iPkts, int iBytes)
+            : m_iPktsCount(iPkts)
+            , m_iBytesCount(iBytes)
+        {
+        }
+
+        Sample operator+(const Sample& other)
+        {
+            return Sample(m_iPktsCount + other.m_iPktsCount, m_iBytesCount + other.m_iBytesCount);
+        }
+
+        Sample& operator+=(const Sample& other)
+        {
+            *this = *this + other;
+            return *this;
+        }
+
+        bool empty() const { return m_iPktsCount == 0; }
+    };
+
+    srt::FixedArray<Sample> m_Samples; // Table of stored data
+
+    /// This method will compute the average value based on all table's measures and the period
+    /// (NUM_PERIODS*SAMPLE_DURATION_MS)
+    void computeAverageValue();
+
+    /// Reset a part of the stored measures
+    /// @param from The beginning where the reset have to be applied
+    /// @param to   The last data that have to be reset
+    void resetRate(int from, int to);
 };
 
 } // namespace srt

srtcore/core.cpp

@@ -7665,10 +7665,15 @@ void srt::CUDT::bstats(CBytePerfMon *perf, bool clear, bool instantaneous)
         perf->pktRcvUndecryptTotal  = m_stats.rcvr.undecrypted.total.count();
         perf->byteRcvUndecryptTotal = m_stats.rcvr.undecrypted.total.bytes();
 
+        
+        // Average values management
+        // We are updating rate with 0 Byte 0 packet to ensure an up to date compute in case we are not sending packet for a while.
+        m_stats.sndr.updateRate(0, 0);
+        m_stats.rcvr.updateRate(0, 0);
+        perf->mbpsSendRate = Bps2Mbps(m_stats.sndr.getAverageValue());
+        perf->mbpsRecvRate = Bps2Mbps(m_stats.rcvr.getAverageValue());
+
         // TODO: The following class members must be protected with a different mutex, not the m_StatsLock.
-        const double interval     = (double) count_microseconds(currtime - m_stats.tsLastSampleTime);
-        perf->mbpsSendRate        = double(perf->byteSent) * 8.0 / interval;
-        perf->mbpsRecvRate        = double(perf->byteRecv) * 8.0 / interval;
         perf->usPktSndPeriod      = (double) count_microseconds(m_tdSendInterval.load());
         perf->pktFlowWindow       = m_iFlowWindowSize.load();
         perf->pktCongestionWindow = m_iCongestionWindow;
@@ -9836,6 +9841,7 @@ bool srt::CUDT::packData(CPacket& w_packet, steady_clock::time_point& w_nexttime
     m_stats.sndr.sent.count(payload);
     if (new_packet_packed)
         m_stats.sndr.sentUnique.count(payload);
+    m_stats.sndr.updateRate(1, payload);
     leaveCS(m_StatsLock);
 
     const duration sendint = m_tdSendInterval;
@@ -10520,6 +10526,7 @@ int srt::CUDT::processData(CUnit* in_unit)
 
     enterCS(m_StatsLock);
     m_stats.rcvr.recvd.count(pktsz);
+    m_stats.rcvr.updateRate(1, pktsz);
     leaveCS(m_StatsLock);
 
     loss_seqs_t                             filter_loss_seqs;

srtcore/stats.h

@@ -13,6 +13,7 @@
 
 #include "platform_sys.h"
 #include "packet.h"
+#include "buffer_tools.h"
 
 namespace srt
 {
@@ -144,6 +145,8 @@ struct Sender
     Metric<Packets> recvdAck; // The number of ACK packets received by the sender.
     Metric<Packets> recvdNak; // The number of ACK packets received by the sender.
 
+    CMovingRateEstimator mavgRateEstimator; // The average Mbps over last second
+
     void reset()
     {
         sent.reset();
@@ -167,6 +170,12 @@ struct Sender
         recvdNak.resetTrace();
         sentFilterExtra.resetTrace();
     }
+
+    void updateRate(int pkts, double bytes) { mavgRateEstimator.addSample(pkts, bytes); }
+
+    void resetRate() { mavgRateEstimator.resetRate(); }
+
+    int getAverageValue() { return mavgRateEstimator.getRate(); }
 };
 
 /// Receiver-side statistics.
@@ -187,6 +196,8 @@ struct Receiver
     Metric<Packets> sentAck; // The number of ACK packets sent by the receiver.
     Metric<Packets> sentNak; // The number of NACK packets sent by the receiver.
 
+    CMovingRateEstimator mavgRateEstimator; // The average Mbps over last second
+
     void reset()
     {
         recvd.reset();
@@ -218,6 +229,12 @@ struct Receiver
         sentAck.resetTrace();
         sentNak.resetTrace();
     }
+
+    void updateRate(int pkts, double bytes) { mavgRateEstimator.addSample(pkts, bytes); }
+
+    void resetRate() { mavgRateEstimator.resetRate(); }
+
+    int getAverageValue() { return mavgRateEstimator.getRate(); }
 };
 
 } // namespace stats