Worked around the increased BDBR regression issue.

The regression was caused by the tile group implementation (PR #348),
when ImproveSharpness is used, as it would impact the QP values of
each CU and latter mode decision process.

So temporarily work around the issue and need to fix it in the future.

Signed-off-by: Austin Hu <austin.hu@intel.com>

Source/Lib/Codec/EbPictureDecisionProcess.c

@@ -1020,9 +1020,14 @@ void* PictureDecisionKernel(void *inputPtr)
 
                         pictureControlSetPtr->disableTmvpFlag = sequenceControlSetPtr->staticConfig.unrestrictedMotionVector == 0 ? EB_TRUE : EB_FALSE;
 
+                        // FIXME: work around the increased BDBR regression issue induced by the
+                        // tile group implementation (PR #348), when ImproveSharpness is used.
+#if 0
                         pictureControlSetPtr->useSrcRef = (sequenceControlSetPtr->staticConfig.improveSharpness && pictureControlSetPtr->temporalLayerIndex > 0) ?
                             EB_TRUE :
                             EB_FALSE;
+#endif
+                        pictureControlSetPtr->useSrcRef = EB_FALSE;
 
                         SignalDerivationMultiProcessesOq(
                                 sequenceControlSetPtr,