Checking scale factors on access.

It is possible to have invalid scale factors and not access them
during decoding. Error is reported if we really try to use invalid scale
factors.

Change-Id: Ie532d3ea7325ee0c7a6ada08269f804350c80fdf

3 files changed, 23 insertions, 22 deletions

diff --git a/vp9/common/vp9_reconinter.c b/vp9/common/vp9_reconinter.c
index 1975e2e76..89c2aa820 100644
--- a/vp9/common/vp9_reconinter.c
+++ b/vp9/common/vp9_reconinter.c
@@ -253,7 +253,7 @@ void vp9_setup_scale_factors(VP9_COMMON *cm, int i) {
     vp9_zero(*sf);
   } else {
     YV12_BUFFER_CONFIG *const fb = &cm->yv12_fb[ref];
-    vp9_setup_scale_factors_for_frame(cm, sf,
+    vp9_setup_scale_factors_for_frame(sf,
                                       fb->y_crop_width, fb->y_crop_height,
                                       cm->width, cm->height);
 
diff --git a/vp9/common/vp9_scale.c b/vp9/common/vp9_scale.c
index 12acac1c9..0b8dc23ea 100644
--- a/vp9/common/vp9_scale.c
+++ b/vp9/common/vp9_scale.c
@@ -10,7 +10,6 @@
 
 #include "./vp9_rtcd.h"
 #include "vp9/common/vp9_filter.h"
-#include "vp9/common/vp9_onyxc_int.h"
 #include "vp9/common/vp9_scale.h"
 
 static INLINE int scaled_x(int val, const struct scale_factors *scale) {
@@ -70,33 +69,32 @@ static int check_scale_factors(int other_w, int other_h,
          this_h <= 16 * other_h;
 }
 
-void vp9_setup_scale_factors_for_frame(struct VP9Common *cm,
-                                       struct scale_factors *scale,
+void vp9_setup_scale_factors_for_frame(struct scale_factors *scale,
                                        int other_w, int other_h,
                                        int this_w, int this_h) {
-  if (!check_scale_factors(other_w, other_h, this_w, this_h))
-    vpx_internal_error(&cm->error, VPX_CODEC_UNSUP_BITSTREAM,
-                       "Invalid scale factors");
-
+  if (!check_scale_factors(other_w, other_h, this_w, this_h)) {
+    scale->x_scale_fp = VP9_REF_INVALID_SCALE;
+    scale->y_scale_fp = VP9_REF_INVALID_SCALE;
+    return;
+  }
 
   scale->x_scale_fp = get_fixed_point_scale_factor(other_w, this_w);
-  scale->x_offset_q4 = 0;  // calculated per block
-  scale->x_step_q4 = scaled_x(16, scale);
-
   scale->y_scale_fp = get_fixed_point_scale_factor(other_h, this_h);
-  scale->y_offset_q4 = 0;  // calculated per block
+  scale->x_step_q4 = scaled_x(16, scale);
   scale->y_step_q4 = scaled_y(16, scale);
+  scale->x_offset_q4 = 0;  // calculated per block
+  scale->y_offset_q4 = 0;  // calculated per block
 
-  if (other_w == this_w && other_h == this_h) {
-    scale->scale_value_x = unscaled_value;
-    scale->scale_value_y = unscaled_value;
-    scale->set_scaled_offsets = set_offsets_without_scaling;
-    scale->scale_mv = unscaled_mv;
-  } else {
+  if (vp9_is_scaled(scale)) {
     scale->scale_value_x = scaled_x;
     scale->scale_value_y = scaled_y;
     scale->set_scaled_offsets = set_offsets_with_scaling;
     scale->scale_mv = scaled_mv;
+  } else {
+    scale->scale_value_x = unscaled_value;
+    scale->scale_value_y = unscaled_value;
+    scale->set_scaled_offsets = set_offsets_without_scaling;
+    scale->scale_mv = unscaled_mv;
   }
 
   // TODO(agrange): Investigate the best choice of functions to use here
diff --git a/vp9/common/vp9_scale.h b/vp9/common/vp9_scale.h
index e3fcae1fc..827ae9bce 100644
--- a/vp9/common/vp9_scale.h
+++ b/vp9/common/vp9_scale.h
@@ -14,10 +14,9 @@
 #include "vp9/common/vp9_mv.h"
 #include "vp9/common/vp9_convolve.h"
 
-struct VP9Common;
-
 #define VP9_REF_SCALE_SHIFT 14
 #define VP9_REF_NO_SCALE (1 << VP9_REF_SCALE_SHIFT)
+#define VP9_REF_INVALID_SCALE -1
 
 struct scale_factors {
   int x_scale_fp;   // horizontal fixed point scale factor
@@ -35,11 +34,15 @@ struct scale_factors {
   convolve_fn_t predict[2][2][2];  // horiz, vert, avg
 };
 
-void vp9_setup_scale_factors_for_frame(struct VP9Common *cm,
-                                       struct scale_factors *scale,
+void vp9_setup_scale_factors_for_frame(struct scale_factors *scale,
                                        int other_w, int other_h,
                                        int this_w, int this_h);
 
+static int vp9_is_valid_scale(const struct scale_factors *sf) {
+  return sf->x_scale_fp != VP9_REF_INVALID_SCALE &&
+         sf->y_scale_fp != VP9_REF_INVALID_SCALE;
+}
+
 static int vp9_is_scaled(const struct scale_factors *sf) {
   return sf->x_scale_fp != VP9_REF_NO_SCALE ||
          sf->y_scale_fp != VP9_REF_NO_SCALE;