Added context reset when 2nd order coefficients are cleared

As discovered in path 10 of Change Ia12acd2f, reset 2nd order coeffs
without reset of above and left coding context may have introduced
problem that causes encoder/decoder mismatching. This commit added
update to coding context when the 2nd coefficients are cleared.

In addition, this commit also introduced early breakout in the checks
to speed up when coefficients are too significant to be cleared.

Change-Id: I85322a432b11e8af85001525d1e9dc218f9a0bd6

vp8/encoder/encodemb.c

@@ -606,18 +606,24 @@ static void optimize_b(MACROBLOCK *mb, int ib, int type,
     *a = *l = (d->eob != !type);
 }
 
-static void check_reset_2nd_coeffs(MACROBLOCKD *x)
+static void check_reset_2nd_coeffs(MACROBLOCKD *x, int type,
+                                   ENTROPY_CONTEXT *a, ENTROPY_CONTEXT *l)
 {
     int sum=0;
     int i;
     BLOCKD *bd = &x->block[24];
-    int eob_pos = (bd->eob<16)? vp8_default_zig_zag1d[bd->eob]:16;
+
+    if(bd->dequant[0]>=35 && bd->dequant[1]>=35)
+        return;
 
     for(i=0;i<bd->eob;i++)
     {
         int coef = bd->dqcoeff[vp8_default_zig_zag1d[i]];
         sum+= (coef>=0)?coef:-coef;
+        if(sum>=35)
+            return;
     }
+
     /**************************************************************************
     our inverse hadamard transform effectively is weighted sum of all 16 inputs
     with weight either 1 or -1. It has a last stage scaling of (sum+3)>>3. And
@@ -628,12 +634,18 @@ static void check_reset_2nd_coeffs(MACROBLOCKD *x)
     **************************************************************************/
     if(sum < 35)
     {
-        vpx_memset(bd->qcoeff,0,eob_pos*2);
-        vpx_memset(bd->dqcoeff,0,eob_pos*2);
+        for(i=0;i<bd->eob;i++)
+        {
+            int rc = vp8_default_zig_zag1d[i];
+            bd->qcoeff[rc]=0;
+            bd->dqcoeff[rc]=0;
+        }
         bd->eob = 0;
+        *a = *l = (bd->eob != !type);
     }
 }
-static void check_reset_8x8_2nd_coeffs(MACROBLOCKD *x)
+static void check_reset_8x8_2nd_coeffs(MACROBLOCKD *x, int type,
+                                   ENTROPY_CONTEXT *a, ENTROPY_CONTEXT *l)
 {
     int sum=0;
     int i;
@@ -668,6 +680,7 @@ static void check_reset_8x8_2nd_coeffs(MACROBLOCKD *x)
         bd->qcoeff[8] = 0;
         bd->dqcoeff[8] = 0;
         bd->eob = 0;
+        *a = *l = (bd->eob != !type);
     }
 }
 
@@ -709,7 +722,8 @@ static void optimize_mb(MACROBLOCK *x, const VP8_ENCODER_RTCD *rtcd)
         b=24;
         optimize_b(x, b, PLANE_TYPE_Y2,
             ta + vp8_block2above[b], tl + vp8_block2left[b], rtcd);
-        check_reset_2nd_coeffs(&x->e_mbd);
+        check_reset_2nd_coeffs(&x->e_mbd, PLANE_TYPE_Y2,
+            ta + vp8_block2above[b], tl + vp8_block2left[b]);
     }
 }
 
@@ -752,7 +766,8 @@ void vp8_optimize_mby(MACROBLOCK *x, const VP8_ENCODER_RTCD *rtcd)
         b=24;
         optimize_b(x, b, PLANE_TYPE_Y2,
             ta + vp8_block2above[b], tl + vp8_block2left[b], rtcd);
-        check_reset_2nd_coeffs(&x->e_mbd);
+        check_reset_2nd_coeffs(&x->e_mbd, PLANE_TYPE_Y2,
+            ta + vp8_block2above[b], tl + vp8_block2left[b]);
     }
 }
 
@@ -1110,7 +1125,9 @@ void optimize_mb_8x8(MACROBLOCK *x, const VP8_ENCODER_RTCD *rtcd)
 
     }
     //8x8 always have 2nd roder haar block
-    check_reset_8x8_2nd_coeffs(&x->e_mbd);
+    check_reset_8x8_2nd_coeffs(&x->e_mbd, PLANE_TYPE_Y2,
+            ta + vp8_block2above[24], tl + vp8_block2left[24]);
+
 }
 
 void vp8_optimize_mby_8x8(MACROBLOCK *x, const VP8_ENCODER_RTCD *rtcd)
@@ -1176,7 +1193,8 @@ void vp8_optimize_mby_8x8(MACROBLOCK *x, const VP8_ENCODER_RTCD *rtcd)
     }
 
     //8x8 always have 2nd roder haar block
-    check_reset_8x8_2nd_coeffs(&x->e_mbd);
+    check_reset_8x8_2nd_coeffs(&x->e_mbd, PLANE_TYPE_Y2,
+            ta + vp8_block2above[24], tl + vp8_block2left[24]);
 }
 
 void vp8_optimize_mbuv_8x8(MACROBLOCK *x, const VP8_ENCODER_RTCD *rtcd)