JVET-T0064 Addition of ALF filter strength control to VTM

cfg/encoder_intra_vtm.cfg

@@ -88,6 +88,7 @@ LMChroma                     : 1      # use CCLM only
 DepQuant                     : 1
 IMV                          : 1
 ALF                          : 1
+ALFStrength                  : 1.0
 IBC                          : 0      # turned off in CTC
 AllowDisFracMMVD             : 1
 AffineAmvr                   : 0

cfg/encoder_lowdelay_P_vtm.cfg

@@ -111,6 +111,7 @@ LMChroma                     : 1      # use CCLM only
 DepQuant                     : 1
 IMV                          : 1
 ALF                          : 1
+ALFStrength                  : 1.0
 CIIP                         : 1
 IBC                          : 0      # turned off in CTC
 AllowDisFracMMVD             : 1

cfg/encoder_lowdelay_vtm.cfg

@@ -112,6 +112,7 @@ LMChroma                     : 1      # use CCLM only
 DepQuant                     : 1
 IMV                          : 1
 ALF                          : 1
+ALFStrength                  : 1.0
 BCW                          : 1
 BcwFast                      : 1
 CIIP                         : 1

cfg/encoder_randomaccess_vtm.cfg

@@ -140,6 +140,7 @@ LMChroma                     : 1      # use CCLM only
 DepQuant                     : 1
 IMV                          : 1
 ALF                          : 1
+ALFStrength                  : 1.0
 BCW                          : 1
 BcwFast                      : 1
 BIO                          : 1

cfg/encoder_randomaccess_vtm_gop16.cfg

@@ -124,6 +124,7 @@ LMChroma                     : 1      # use CCLM only
 DepQuant                     : 1
 IMV                          : 1
 ALF                          : 1
+ALFStrength                  : 1.0
 BCW                          : 1
 BcwFast                      : 1
 BIO                          : 1

doc/software-manual.tex

@@ -2888,6 +2888,12 @@ switched at CTB level. Set to 1 to disable alternative chroma filters.
 Value shall be in the range 1..8.
 \\
 
+\Option{ALFStrength} &
+%\ShortOption{\None} &
+\Default{1.0} &
+Enables control of ALF filter strength. The parameter scales the magnitudes of the ALF filter coefficients for both luma and chroma.
+\\
+
 \Option{CCALF} &
 %\ShortOption{\None} &
 \Default{true} &

source/App/EncoderApp/EncApp.cpp

@@ -1048,6 +1048,9 @@ void EncApp::xInitLibCfg()
   m_cEncLib.setForceSingleSplitThread                            ( m_forceSplitSequential );
 #endif
   m_cEncLib.setUseALF                                            ( m_alf );
+#if JVET_T0064
+  m_cEncLib.setALFStrength                                       (m_alfStrength);
+#endif
   m_cEncLib.setUseCCALF                                          ( m_ccalf );
   m_cEncLib.setCCALFQpThreshold                                  ( m_ccalfQpThreshold );
   m_cEncLib.setLmcs                                              ( m_lmcsEnabled );

source/App/EncoderApp/EncAppCfg.cpp

@@ -1403,6 +1403,9 @@ bool EncAppCfg::parseCfg( int argc, char* argv[] )
   ("DebugCTU",                                        m_debugCTU,                                  -1, "If DebugBitstream is present, load frames up to this POC from this bitstream. Starting with DebugPOC-frame at CTUline containin debug CTU.")
   ("EnsureWppBitEqual",                               m_ensureWppBitEqual,                      false, "Ensure the results are equal to results with WPP-style parallelism, even if WPP is off")
   ( "ALF",                                             m_alf,                                    true, "Adaptive Loop Filter\n" )
+#if JVET_T0064
+  ("ALFStrength", m_alfStrength, 1.0, "Adaptive Loop Filter strength. The parameter scales the magnitudes of the ALF filter coefficients for both luma and chroma.")
+#endif
   ( "CCALF",                                           m_ccalf,                                  true, "Cross-component Adaptive Loop Filter" )
   ( "CCALFQpTh",                                       m_ccalfQpThreshold,                         37, "QP threshold above which encoder reduces CCALF usage")
   ( "RPR",                                            m_rprEnabledFlag,                          true, "Reference Sample Resolution" )

source/App/EncoderApp/EncAppCfg.h

@@ -694,6 +694,9 @@ protected:
   bool        m_forceDecodeBitstream1;
 
   bool        m_alf;                                          ///< Adaptive Loop Filter
+#if JVET_T0064
+  double      m_alfStrength;
+#endif
   bool        m_ccalf;
   int         m_ccalfQpThreshold;
 

source/Lib/CommonLib/TypeDef.h

@@ -69,6 +69,8 @@
 #define JVET_S0175_ASPECT5                                1 // use u(8) instead of u(4) for (ffi_)display_elemental_periods_minus1 and pt_display_elemental_periods_minus1
 #define JVET_S0175_ASPECT6                                1 // The general_nal_hrd_params_present_flag and general_vcl_hrd_params_present_flag are allowed to both be equal to 0
 #define JVET_R0046_IRAP_ASPECT2                           1 // Add a constraint on an ILRP being either an IRAP picture or having TemporalId less than or equal to Max (0, vps_max_tid_il_ref_pics_plus1[ refPicVpsLayerId ] - 1 )
+#define JVET_T0064                                        1 // JVET-T0064: control of filter strength for ALF
+
 
 //########### place macros to be be kept below this line ###############
 #define JVET_S0257_DUMP_360SEI_MESSAGE                    1 // Software support of 360 SEI messages

source/Lib/EncoderLib/EncAdaptiveLoopFilter.cpp

@@ -1834,7 +1834,12 @@ double EncAdaptiveLoopFilter::deriveCoeffQuant( int *filterClipp, int *filterCoe
   filterCoeffQuant[numCoeff - 1] = 0;
 
   int modified=1;
-
+#if JVET_T0064
+  if( m_encCfg->getALFStrength() != 1.0 )
+  {
+    modified = 0;
+  }
+#endif
   double errRef=cov.calcErrorForCoeffs( filterClipp, filterCoeffQuant, numCoeff, bitDepth );
   while( modified )
   {
@@ -1878,7 +1883,11 @@ void EncAdaptiveLoopFilter::roundFiltCoeff( int *filterCoeffQuant, double *filte
   for( int i = 0; i < numCoeff; i++ )
   {
     int sign = filterCoeff[i] > 0 ? 1 : -1;
+#if JVET_T0064
+    filterCoeffQuant[i] = int((filterCoeff[i] * m_encCfg->getALFStrength()) * sign * factor + 0.5) * sign;
+#else
     filterCoeffQuant[i] = int( filterCoeff[i] * sign * factor + 0.5 ) * sign;
+#endif
   }
 }
 
@@ -2721,7 +2730,16 @@ void  EncAdaptiveLoopFilter::alfEncoderCtb(CodingStructure& cs, AlfParam& alfPar
           double         costOn = MAX_DOUBLE;
           ctxTempStart = AlfCtx(m_CABACEstimator->getCtx());
           int iBestFilterSetIdx = 0;
+#if JVET_T0064
+          int firstFilterSetIdx = 0;
+          if (m_encCfg->getALFStrength() != 1.0)
+          {
+            firstFilterSetIdx = NUM_FIXED_FILTER_SETS;
+          }
+          for (int filterSetIdx = firstFilterSetIdx; filterSetIdx < numFilterSet; filterSetIdx++)
+#else
           for (int filterSetIdx = 0; filterSetIdx < numFilterSet; filterSetIdx++)
+#endif
           {
             //rate
             m_CABACEstimator->getCtx() = AlfCtx(ctxTempStart);

source/Lib/EncoderLib/EncCfg.h

@@ -738,6 +738,9 @@ protected:
 #endif
 
   bool        m_alf;                                          ///< Adaptive Loop Filter
+#if JVET_T0064
+  double      m_alfStrength;
+#endif
   bool        m_ccalf;
   int         m_ccalfQpThreshold;
 #if JVET_O0756_CALCULATE_HDRMETRICS
@@ -1923,6 +1926,10 @@ public:
 #endif
   void         setUseALF( bool b ) { m_alf = b; }
   bool         getUseALF()                                      const { return m_alf; }
+#if JVET_T0064
+  void         setALFStrength( double s) { m_alfStrength = s; }
+  double       getALFStrength()                                 const { return m_alfStrength; }
+#endif
   void         setUseCCALF( bool b )                                  { m_ccalf = b; }
   bool         getUseCCALF()                                    const { return m_ccalf; }
   void         setCCALFQpThreshold( int b )                           { m_ccalfQpThreshold = b; }