Adds feature for companded MV encoding

The high-precision (1/8) pel bit is turned off if the reference
MV is larger than a threshold. The motivation for this patch is
the intuition that if motion is likely large (as indicated by
the reference), there is likley to be more motion blur, and as
a result 1/8 pel precision would be wasteful both in rd sense
as well as computationally.

The feature is incorporated as part of the newmventropy experiment.
There is a modest RD improvement with the patch. Overall the
results with the newmventropy experiment with the threshold being
16 integer pels are:

derf: +0.279%
std-hd: +0.617%
hd: +1.299%
yt: +0.822%

With threshold 8 integer pels are:

derf: +0.295%
std-hd: +0.623%
hd: +1.365%
yt: +0.847%

Patch: rebased
Patch: rebase fixes

Change-Id: I4ed14600df3c457944e6541ed407cb6e91fe428b

2 files changed, 20 insertions, 3 deletions

diff --git a/vp8/encoder/encodemv.c b/vp8/encoder/encodemv.c
index 217cc00c5..1289d89bb 100644
--- a/vp8/encoder/encodemv.c
+++ b/vp8/encoder/encodemv.c
@@ -526,6 +526,7 @@ void vp8_encode_nmv(vp8_writer *w, const MV *mv, const MV *ref,
 void vp8_encode_nmv_fp(vp8_writer *w, const MV *mv, const MV *ref,
                        const nmv_context *mvctx, int usehp) {
   MV_JOINT_TYPE j = vp8_get_mv_joint(*mv);
+  usehp = usehp && vp8_use_nmv_hp(ref);
   if (j == MV_JOINT_HZVNZ || j == MV_JOINT_HNZVNZ) {
     encode_nmv_component_fp(w, mv->row, ref->row, &mvctx->comps[0], usehp);
   }
diff --git a/vp8/encoder/mcomp.c b/vp8/encoder/mcomp.c
index 76accd423..a6cf2f18b 100644
--- a/vp8/encoder/mcomp.c
+++ b/vp8/encoder/mcomp.c
@@ -276,6 +276,7 @@ int vp8_find_best_sub_pixel_step_iteratively(MACROBLOCK *x, BLOCK *b, BLOCKD *d,
   int maxc, minc, maxr, minr;
   int y_stride;
   int offset;
+  int usehp = xd->allow_high_precision_mv;
 
 #if !CONFIG_SUPERBLOCKS && (ARCH_X86 || ARCH_X86_64)
   unsigned char *y0 = *(d->base_pre) + d->pre + (bestmv->as_mv.row) * d->pre_stride + bestmv->as_mv.col;
@@ -301,7 +302,6 @@ int vp8_find_best_sub_pixel_step_iteratively(MACROBLOCK *x, BLOCK *b, BLOCKD *d,
   y_stride = d->pre_stride;
 #endif
 
-
   rr = ref_mv->as_mv.row;
   rc = ref_mv->as_mv.col;
   br = bestmv->as_mv.row << 3;
@@ -403,7 +403,15 @@ int vp8_find_best_sub_pixel_step_iteratively(MACROBLOCK *x, BLOCK *b, BLOCKD *d,
     tc = bc;
   }
 
-  if (x->e_mbd.allow_high_precision_mv) {
+#if CONFIG_NEWMVENTROPY
+  if (xd->allow_high_precision_mv) {
+    usehp = vp8_use_nmv_hp(&ref_mv->as_mv);
+  } else {
+    usehp = 0;
+  }
+#endif
+
+  if (usehp) {
     hstep >>= 1;
     while (--eighthiters) {
       CHECK_BETTER(left, tr, tc - hstep);
@@ -471,6 +479,7 @@ int vp8_find_best_sub_pixel_step(MACROBLOCK *x, BLOCK *b, BLOCKD *d,
   int thismse;
   int y_stride;
   MACROBLOCKD *xd = &x->e_mbd;
+  int usehp = xd->allow_high_precision_mv;
 
 #if !CONFIG_SUPERBLOCKS && (ARCH_X86 || ARCH_X86_64)
   unsigned char *y0 = *(d->base_pre) + d->pre + (bestmv->as_mv.row) * d->pre_stride + bestmv->as_mv.col;
@@ -762,7 +771,14 @@ int vp8_find_best_sub_pixel_step(MACROBLOCK *x, BLOCK *b, BLOCKD *d,
     *sse1 = sse;
   }
 
-  if (!x->e_mbd.allow_high_precision_mv)
+#if CONFIG_NEWMVENTROPY
+  if (x->e_mbd.allow_high_precision_mv) {
+    usehp = vp8_use_nmv_hp(&ref_mv->as_mv);
+  } else {
+    usehp = 0;
+  }
+#endif
+  if (!usehp)
     return bestmse;
 
   /* Now do 1/8th pixel */