diff --git a/av1/common/scale.h b/av1/common/scale.h
new file mode 100644
index 0000000..bb02601
--- /dev/null
+++ b/av1/common/scale.h
@@ -0,0 +1,79 @@
+/*
+ *  Copyright (c) 2013 The WebM project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef VP10_COMMON_SCALE_H_
+#define VP10_COMMON_SCALE_H_
+
+#include "av1/common/mv.h"
+#include "aom_dsp/vpx_convolve.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#define REF_SCALE_SHIFT 14
+#define REF_NO_SCALE (1 << REF_SCALE_SHIFT)
+#define REF_INVALID_SCALE -1
+
+struct scale_factors {
+  int x_scale_fp;  // horizontal fixed point scale factor
+  int y_scale_fp;  // vertical fixed point scale factor
+  int x_step_q4;
+  int y_step_q4;
+
+  int (*scale_value_x)(int val, const struct scale_factors *sf);
+  int (*scale_value_y)(int val, const struct scale_factors *sf);
+
+  convolve_fn_t predict[2][2][2];  // horiz, vert, avg
+#if CONFIG_VP9_HIGHBITDEPTH
+  highbd_convolve_fn_t highbd_predict[2][2][2];  // horiz, vert, avg
+#endif                                           // CONFIG_VP9_HIGHBITDEPTH
+
+// Functions for non-interpolating filters (those that filter zero offsets)
+#if CONFIG_EXT_INTERP && SUPPORT_NONINTERPOLATING_FILTERS
+  convolve_fn_t predict_ni[2][2][2];  // horiz, vert, avg
+#if CONFIG_VP9_HIGHBITDEPTH
+  highbd_convolve_fn_t highbd_predict_ni[2][2][2];  // horiz, vert, avg
+#endif                                              // CONFIG_VP9_HIGHBITDEPTH
+#endif  // CONFIG_EXT_INTERP && SUPPORT_NONINTERPOLATING_FILTERS
+};
+
+MV32 vp10_scale_mv(const MV *mv, int x, int y, const struct scale_factors *sf);
+
+#if CONFIG_VP9_HIGHBITDEPTH
+void vp10_setup_scale_factors_for_frame(struct scale_factors *sf, int other_w,
+                                        int other_h, int this_w, int this_h,
+                                        int use_high);
+#else
+void vp10_setup_scale_factors_for_frame(struct scale_factors *sf, int other_w,
+                                        int other_h, int this_w, int this_h);
+#endif  // CONFIG_VP9_HIGHBITDEPTH
+
+static INLINE int vp10_is_valid_scale(const struct scale_factors *sf) {
+  return sf->x_scale_fp != REF_INVALID_SCALE &&
+         sf->y_scale_fp != REF_INVALID_SCALE;
+}
+
+static INLINE int vp10_is_scaled(const struct scale_factors *sf) {
+  return vp10_is_valid_scale(sf) &&
+         (sf->x_scale_fp != REF_NO_SCALE || sf->y_scale_fp != REF_NO_SCALE);
+}
+
+static INLINE int valid_ref_frame_size(int ref_width, int ref_height,
+                                       int this_width, int this_height) {
+  return 2 * this_width >= ref_width && 2 * this_height >= ref_height &&
+         this_width <= 16 * ref_width && this_height <= 16 * ref_height;
+}
+
+#ifdef __cplusplus
+}  // extern "C"
+#endif
+
+#endif  // VP10_COMMON_SCALE_H_