WIP: JVET-O0637 Choose line0 and line3 for gradient computation when chroma is same size as luma

source/Lib/CommonLib/LoopFilter.cpp

@@ -1206,18 +1206,33 @@ void LoopFilter::xEdgeFilterChroma(const CodingUnit& cu, const DeblockEdgeDir ed
 
         const int dp0 = xCalcDP(piTmpSrcChroma + iSrcStep*(iIdx*uiLoopLength + 0), iOffset);
         const int dq0 = xCalcDQ(piTmpSrcChroma + iSrcStep*(iIdx*uiLoopLength + 0), iOffset);
+#if JVET_O0637_CHROMA_GRADIENT_LINE_SELECTION
+        const int subSamplingShift = ( edgeDir == EDGE_VER ) ? m_shiftVer : m_shiftHor;
+        const int dp3 = ( subSamplingShift == 1 ) ? xCalcDP(piTmpSrcChroma + iSrcStep*(iIdx*uiLoopLength + 1), iOffset) : xCalcDP(piTmpSrcChroma + iSrcStep*(iIdx*uiLoopLength + 3), iOffset);
+        const int dq3 = ( subSamplingShift == 1 ) ? xCalcDQ(piTmpSrcChroma + iSrcStep*(iIdx*uiLoopLength + 1), iOffset) : xCalcDQ(piTmpSrcChroma + iSrcStep*(iIdx*uiLoopLength + 3), iOffset);
+#else
         const int dp1 = xCalcDP(piTmpSrcChroma + iSrcStep*(iIdx*uiLoopLength + 1), iOffset);
         const int dq1 = xCalcDQ(piTmpSrcChroma + iSrcStep*(iIdx*uiLoopLength + 1), iOffset);
+#endif
 
         const int d0 = dp0 + dq0;
+#if JVET_O0637_CHROMA_GRADIENT_LINE_SELECTION
+        const int d3 = dp3 + dq3;
+        const int d = d0 + d3;
+#else
         const int d1 = dp1 + dq1;
         const int d = d0 + d1;
+#endif
 
           if (d < beta)
           {
             useLongFilter = true;
             const bool sw = xUseStrongFiltering(piTmpSrcChroma + iSrcStep*(iIdx*uiLoopLength + 0), iOffset, 2 * d0, beta, iTc)
+#if JVET_O0637_CHROMA_GRADIENT_LINE_SELECTION
+                && xUseStrongFiltering(piTmpSrcChroma + iSrcStep*(iIdx*uiLoopLength + ( ( subSamplingShift == 1 ) ? 1 : 3 ) ), iOffset, 2 * d3, beta, iTc);
+#else
                 && xUseStrongFiltering(piTmpSrcChroma + iSrcStep*(iIdx*uiLoopLength + 1), iOffset, 2 * d1, beta, iTc);
+#endif
 
             for (unsigned step = 0; step < uiLoopLength; step++)
             {

source/Lib/CommonLib/TypeDef.h

@@ -52,6 +52,8 @@
 
 #define JVET_O0247_ALF_CTB_CODING_REDUNDANCY_REMOVAL      1 // JVET-O0247: not signal APS index when number APS is 2
 
+#define JVET_O0637_CHROMA_GRADIENT_LINE_SELECTION         1 // Choose line0 and line3 for gradient computation when chroma is same size as luma
+
 #define JVET_O0288_UNIFY_ALF_SLICE_TYPE_REMOVAL           1 // JVET-O0288: remove slice type dependency in ALF
 
 #define JVET_O0064_SIMP_ALF_CLIP_CODING                   1 // JVET-O0047/O0058/O0064/O0067/O0290/O0301/O0430: use FLC for alf clipping indices, always signal alf clipping indices