allow_warp: rectify mismatch between spec and code

As per the spec, we must compare the scales at higher precision in this
function to check if there is a rescale.

So, we use the av1_is_scaled() function that looks at the fixed point
scales.

BUG=aomedia:2191

Change-Id: I9276dc6f54fe01deb98549ac4ebcc25fae462cf2

av1/common/reconinter.c

diff --git a/av1/common/reconinter.c b/av1/common/reconinter.c
index 21d3534..f6e5b11 100644
--- a/av1/common/reconinter.c
+++ b/av1/common/reconinter.c
@@ -35,10 +35,12 @@
 int av1_allow_warp(const MB_MODE_INFO *const mbmi,
                    const WarpTypesAllowed *const warp_types,
                    const WarpedMotionParams *const gm_params,
-                   int build_for_obmc, int x_scale, int y_scale,
+                   int build_for_obmc, const struct scale_factors *const sf,
                    WarpedMotionParams *final_warp_params) {
-  if (x_scale != SCALE_SUBPEL_SHIFTS || y_scale != SCALE_SUBPEL_SHIFTS)
-    return 0;
+  // Note: As per the spec, we must test the fixed point scales here, which are
+  // at a higher precision (1 << 14) than the xs and ys in subpel_params (that
+  // have 1 << 10 precision).
+  if (av1_is_scaled(sf)) return 0;
 
   if (final_warp_params != NULL) *final_warp_params = default_warp_params;
 
@@ -75,8 +77,7 @@
   const int do_warp =
       (w >= 8 && h >= 8 &&
        av1_allow_warp(mi, warp_types, &xd->global_motion[mi->ref_frame[ref]],
-                      build_for_obmc, subpel_params->xs, subpel_params->ys,
-                      &final_warp_params));
+                      build_for_obmc, sf, &final_warp_params));
   const int is_intrabc = mi->use_intrabc;
   assert(IMPLIES(is_intrabc, !do_warp));
 

av1/common/reconinter.h

diff --git a/av1/common/reconinter.h b/av1/common/reconinter.h
index db86c77..b98b0ca 100644
--- a/av1/common/reconinter.h
+++ b/av1/common/reconinter.h
@@ -355,7 +355,7 @@
 int av1_allow_warp(const MB_MODE_INFO *const mbmi,
                    const WarpTypesAllowed *const warp_types,
                    const WarpedMotionParams *const gm_params,
-                   int build_for_obmc, int x_scale, int y_scale,
+                   int build_for_obmc, const struct scale_factors *const sf,
                    WarpedMotionParams *final_warp_params);
 
 #ifdef __cplusplus

av1/decoder/decodeframe.c

diff --git a/av1/decoder/decodeframe.c b/av1/decoder/decodeframe.c
index ae32a0b..f4aa4a3 100644
--- a/av1/decoder/decodeframe.c
+++ b/av1/decoder/decodeframe.c
@@ -789,8 +789,7 @@
       int do_warp = (bw >= 8 && bh >= 8 &&
                      av1_allow_warp(mi, &warp_types,
                                     &xd->global_motion[mi->ref_frame[ref]],
-                                    build_for_obmc, subpel_params[ref].xs,
-                                    subpel_params[ref].ys, NULL));
+                                    build_for_obmc, sf, NULL));
       do_warp = (do_warp && xd->cur_frame_force_integer_mv == 0);
 
       extend_mc_border(sf, pre_buf, scaled_mv, block, subpel_x_mv, subpel_y_mv,