improved jitter buffer correction algorithm

src/buffer.cpp

@@ -41,6 +41,9 @@ void CNetBuf::Init ( const int iNewBlockSize,
 
     // use the "get" flag to make sure the buffer is cleared
     Clear ( CT_GET );
+
+    // init statistic
+    ErrorRateStatistic.Init ( MAX_STATISTIC_COUNT );
 }
 
 bool CNetBuf::Put ( const CVector<uint8_t>& vecbyData,
@@ -103,6 +106,9 @@ bool CNetBuf::Put ( const CVector<uint8_t>& vecbyData,
         eBufState = CNetBuf::BS_OK;
     }
 
+    // update statistic
+    ErrorRateStatistic.Update ( !bPutOK );
+
     return bPutOK;
 }
 
@@ -184,6 +190,9 @@ bool CNetBuf::Get ( CVector<uint8_t>& vecbyData )
         eBufState = CNetBuf::BS_OK;
     }
 
+    // update statistic
+    ErrorRateStatistic.Update ( !bGetOK );
+
     return bGetOK;
 }
 
@@ -231,14 +240,52 @@ int CNetBuf::GetAvailData() const
 
 void CNetBuf::Clear ( const EClearType eClearType )
 {
-// TEST defines
-const bool bUseRandomInit           = false;
-const int  iNumBlocksBoundForRandom = 6;
+    // Define the number of blocks bound for the "random offset" (1) algorithm.
+    // If we are above the bound, we use the "middle of buffer" (2) algorithm.
+    // Test results (with different jitter buffer sizes), given is the error
+    // probability of jitter buffer (probability of corrections in the buffer):
+    //  kX, 128 samples, WLAN:
+    //      2: (1) 5 %,    (2) 12.3 %
+    //      3: (1) 18.3 %, (2) 17.1 %
+    //      5: (1) 0.9 %,  (2) 0.8 %
+    //  kX, 128 samples, localhost:
+    //      2: (1) 2.5 %,  (2) 13 %
+    //      3: (1) 0.9 %,  (2) 1.1 %
+    //      5: (1) 0.7 %,  (2) 0.6 %
+    //  Behringer, 128 samples, WLAN:
+    //      2: (1) 5.8 %,  (2) 9.4 %
+    //      3: (1) 0.9 %,  (2) 0.8 %
+    //      5: (1) 0.4 %,  (2) 0.3 %
+    //  Behringer, 128 samples, localhost:
+    //      2: (1) 1 %,    (2) 9.8 %
+    //      3: (1) 0.57 %, (2) 0.6 %
+    //      5: (1) 0.6 %,  (2) 0.56 %
+    //  kX, 256 samples, WLAN:
+    //      3: (1) 24.2 %, (2) 18.4 %
+    //      4: (1) 1.5 %,  (2) 2.5 %
+    //      5: (1) 1 %,    (2) 1 %
+    //  ASIO4All, 256 samples, WLAN:
+    //      3: (1) 14.9 %, (2) 11.9 %
+    //      4: (1) 1.5 %,  (2) 7 %
+    //      5: (1) 1.2 %,  (2) 1.3 %
+    const int  iNumBlocksBoundInclForRandom = 4; // by extensive testing: 4
 
     int iNewFillLevel = 0;
 
     if ( iBlockSize != 0 )
     {
+        const int iNumBlocks = iMemSize / iBlockSize;
+        if ( iNumBlocks <= iNumBlocksBoundInclForRandom ) // just for small buffers
+        {
+            // random position algorithm
+            // overwrite fill level with random value, the range
+            // is 0 to (iMemSize - iBlockSize)
+            iNewFillLevel = static_cast<int> ( static_cast<double> ( rand() ) *
+                iNumBlocks / RAND_MAX ) * iBlockSize;
+        }
+        else
+        {
+            // middle of buffer algorithm
             // with the following operation we set the fill level to a block
             // boundary (one block below the middle of the buffer in case of odd
             // number of blocks, e.g.:
@@ -246,28 +293,9 @@ const int  iNumBlocksBoundForRandom = 6;
             // 1: 0   /   2: 0   /   3: 1   /   4: 1   /   5: 2 ...)
             iNewFillLevel =
                 ( ( ( iMemSize - iBlockSize) / 2 ) / iBlockSize ) * iBlockSize;
-
-// TEST random init position
-if ( bUseRandomInit )
-{
-    const int iNumBlocks = iMemSize / iBlockSize;
-    if ( iNumBlocks < iNumBlocksBoundForRandom ) // just for very small buffers
-    {
-        // overwrite fill level with random value, the range
-        // is 0 to (iMemSize - iBlockSize)
-        iNewFillLevel = static_cast<int> ( static_cast<double> ( rand() ) *
-            iNumBlocks / RAND_MAX ) * iBlockSize;
         }
     }
 
-/*
-// TEST
-static FILE* pFile = fopen ( "test.dat", "w" );
-fprintf ( pFile, "%d %d %d\n", iMemSize, iBlockSize, iNewFillLevel );
-fflush ( pFile );
-*/
-    }
-
     // different behaviour for get and put corrections
     if ( eClearType == CT_GET )
     {

src/buffer.h

@@ -29,7 +29,14 @@
 #include "global.h"
 
 
+/* Definitions ****************************************************************/
+// each regular buffer access lead to a count for put and get, assuming 2.33 ms
+// blocks we have 30 s / 2.33 ms * 2 = 25714
+#define MAX_STATISTIC_COUNT                 25714
+
+
 /* Classes ********************************************************************/
+// Network buffer (jitter buffer) ----------------------------------------------
 class CNetBuf
 {
 public:
@@ -42,6 +49,8 @@ public:
     bool Put ( const CVector<uint8_t>& vecbyData, const int iInSize );
     bool Get ( CVector<uint8_t>& vecbyData );
 
+    double GetErrorRate() { return ErrorRateStatistic.GetAverage(); }
+
 protected:
     enum EBufState { BS_OK, BS_FULL, BS_EMPTY };
     enum EClearType { CT_PUT, CT_GET };
@@ -55,10 +64,13 @@ protected:
     int              iNumInvalidElements;
     int              iGetPos, iPutPos;
     EBufState        eBufState;
+
+    // statistic
+    CErrorRate       ErrorRateStatistic;
 };
 
 
-// conversion buffer (very simple buffer)
+// Conversion buffer (very simple buffer) --------------------------------------
 template<class TData> class CConvBuf
 {
 public:

src/channel.h

@@ -104,6 +104,7 @@ public:
     int GetNetwFrameSizeFact() const { return iNetwFrameSizeFact; }
     int GetNetwFrameSize() const { return iNetwFrameSize; }
 
+    double GetJitterBufferErrorRate() { return SockBuf.GetErrorRate(); }
 
     // network protocol interface
     void CreateJitBufMes ( const int iJitBufSize )

src/llconclientdlg.cpp

@@ -704,6 +704,7 @@ void CLlconClientDlg::UpdateDisplay()
 
 // TEST
 //TextLabelStatus->setText ( QString( "Time: %1, Netw: %2" ).arg ( pClient->GetTimingStdDev() ).arg ( pClient->GetChannel()->GetTimingStdDev() ) );
+//TextLabelStatus->setText ( QString( "Buf. Err. Rate: %1 %" ).arg ( pClient->GetChannel()->GetJitterBufferErrorRate() * 100.0 ) );
 
 }
 

src/util.h

@@ -562,15 +562,15 @@ public:
 
 
 /******************************************************************************\
-* Cycle Time Variance Measurement                                              *
+* Statistics                                                                   *
 \******************************************************************************/
+// Cycle time variance measurement ---------------------------------------------
 // use for, e.g., measuring the variance of a timer
 class CCycleTimeVariance
 {
 public:
     CCycleTimeVariance() : iBlockLengthAtSystemSampleRate ( 0 ),
         dIntervalTime ( 0.0 ), iNewValueBoundFactor ( 0 ) {}
-    virtual ~CCycleTimeVariance() {}
 
     void Init ( const int iNewBlockLengthAtSystemSampleRate,
                 const int iNewSystemSampleRate,
@@ -644,4 +644,42 @@ protected:
     int               iNewValueBoundFactor;
 };
 
+// Error rate measurement ------------------------------------------------------
+class CErrorRate
+{
+public:
+    CErrorRate() {}
+
+    void Init ( const int iHistoryLength )
+    {
+        // initialize buffer
+        ErrorsMovAvBuf.Init ( iHistoryLength );
+    }
+
+    void Reset()
+    {
+        ErrorsMovAvBuf.Reset();
+    }
+
+    void Update ( const bool bState )
+    {
+        // add errors as values 0 and 1 to get correct error rate average
+        if ( bState )
+        {
+            ErrorsMovAvBuf.Add ( 1.0 );
+        }
+        else
+        {
+            ErrorsMovAvBuf.Add ( 0.0 );
+        }
+    }
+
+    // return the standard deviation, for that we need to calculate
+    // the sqaure root
+    double GetAverage() { return ErrorsMovAvBuf.GetAverage(); }
+
+protected:
+    CMovingAv<double> ErrorsMovAvBuf;
+};
+
 #endif /* !defined ( UTIL_HOIH934256GEKJH98_3_43445KJIUHF1912__INCLUDED_ ) */