diff --git a/source/convert.cc b/source/convert.cc
index 842ef094f..9ec71058c 100644
--- a/source/convert.cc
+++ b/source/convert.cc
@@ -22,7 +22,43 @@ namespace libyuv {
 extern "C" {
 #endif
 
+#define SUBSAMPLE(v, a, s) (v < 0) ? (-((-v + a) >> s)) : ((v + a) >> s)
+static __inline int Abs(int v) {
+  return v >= 0 ? v : -v;
+}
+
+// Any I4xx To I420 format with mirroring.
+static int I4xxToI420(const uint8* src_y, int src_stride_y,
+                      const uint8* src_u, int src_stride_u,
+                      const uint8* src_v, int src_stride_v,
+                      uint8* dst_y, int dst_stride_y,
+                      uint8* dst_u, int dst_stride_u,
+                      uint8* dst_v, int dst_stride_v,
+                      int src_y_width, int src_y_height,
+                      int src_uv_width, int src_uv_height) {
+  if (src_y_width == 0 || src_y_height == 0 ||
+      src_uv_width == 0 || src_uv_height == 0) {
+    return -1;
+  }
+  const int dst_y_width = Abs(src_y_width);
+  const int dst_y_height = Abs(src_y_height);
+  const int dst_uv_width = SUBSAMPLE(dst_y_width, 1, 1);
+  const int dst_uv_height = SUBSAMPLE(dst_y_height, 1, 1);
+  ScalePlane(src_y, src_stride_y, src_y_width, src_y_height,
+             dst_y, dst_stride_y, dst_y_width, dst_y_height,
+             kFilterBilinear);
+  ScalePlane(src_u, src_stride_u, src_uv_width, src_uv_height,
+             dst_u, dst_stride_u, dst_uv_width, dst_uv_height,
+             kFilterBilinear);
+  ScalePlane(src_v, src_stride_v, src_uv_width, src_uv_height,
+             dst_v, dst_stride_v, dst_uv_width, dst_uv_height,
+             kFilterBilinear);
+  return 0;
+}
+
 // Copy I420 with optional flipping
+// TODO(fbarchard): Use Scale plane which supports mirroring, but ensure
+// is does row coalescing.
 LIBYUV_API
 int I420Copy(const uint8* src_y, int src_stride_y,
              const uint8* src_u, int src_stride_u,
@@ -69,37 +105,15 @@ int I422ToI420(const uint8* src_y, int src_stride_y,
                uint8* dst_u, int dst_stride_u,
                uint8* dst_v, int dst_stride_v,
                int width, int height) {
-  if (!src_y || !src_u || !src_v ||
-      !dst_y || !dst_u || !dst_v ||
-      width <= 0 || height == 0) {
-    return -1;
-  }
-  // Negative height means invert the image.
-  if (height < 0) {
-    height = -height;
-    src_y = src_y + (height - 1) * src_stride_y;
-    src_u = src_u + (height - 1) * src_stride_u;
-    src_v = src_v + (height - 1) * src_stride_v;
-    src_stride_y = -src_stride_y;
-    src_stride_u = -src_stride_u;
-    src_stride_v = -src_stride_v;
-  }
-
-  // Copy Y plane
-  if (dst_y) {
-    CopyPlane(src_y, src_stride_y, dst_y, dst_stride_y, width, height);
-  }
-
-  // Resample UV planes.
-  const int halfwidth = (width + 1) >> 1;
-  const int halfheight = (height + 1) >> 1;
-  ScalePlane(src_u, src_stride_u, halfwidth, height,
-             dst_u, dst_stride_u, halfwidth, halfheight,
-             kFilterBilinear);
-  ScalePlane(src_v, src_stride_v, halfwidth, height,
-             dst_v, dst_stride_v, halfwidth, halfheight,
-             kFilterBilinear);
-  return 0;
+  const int src_uv_width = SUBSAMPLE(width, 1, 1);
+  return I4xxToI420(src_y, src_stride_y,
+                    src_u, src_stride_u,
+                    src_v, src_stride_v,
+                    dst_y, dst_stride_y,
+                    dst_u, dst_stride_u,
+                    dst_v, dst_stride_v,
+                    width, height,
+                    src_uv_width, height);
 }
 
 // 444 chroma is 1x width, 1x height
@@ -112,37 +126,14 @@ int I444ToI420(const uint8* src_y, int src_stride_y,
                uint8* dst_u, int dst_stride_u,
                uint8* dst_v, int dst_stride_v,
                int width, int height) {
-  if (!src_y || !src_u || !src_v ||
-      !dst_y || !dst_u || !dst_v ||
-      width <= 0 || height == 0) {
-    return -1;
-  }
-  // Negative height means invert the image.
-  if (height < 0) {
-    height = -height;
-    src_y = src_y + (height - 1) * src_stride_y;
-    src_u = src_u + (height - 1) * src_stride_u;
-    src_v = src_v + (height - 1) * src_stride_v;
-    src_stride_y = -src_stride_y;
-    src_stride_u = -src_stride_u;
-    src_stride_v = -src_stride_v;
-  }
-
-  // Copy Y plane
-  if (dst_y) {
-    CopyPlane(src_y, src_stride_y, dst_y, dst_stride_y, width, height);
-  }
-
-  // Resample UV planes.
-  const int halfwidth = (width + 1) >> 1;
-  const int halfheight = (height + 1) >> 1;
-  ScalePlane(src_u, src_stride_u, width, height,
-             dst_u, dst_stride_u, halfwidth, halfheight,
-             kFilterBilinear);
-  ScalePlane(src_v, src_stride_v, width, height,
-             dst_v, dst_stride_v, halfwidth, halfheight,
-             kFilterBilinear);
-  return 0;
+  return I4xxToI420(src_y, src_stride_y,
+                    src_u, src_stride_u,
+                    src_v, src_stride_v,
+                    dst_y, dst_stride_y,
+                    dst_u, dst_stride_u,
+                    dst_v, dst_stride_v,
+                    width, height,
+                    width, height);
 }
 
 // 411 chroma is 1/4 width, 1x height
@@ -155,38 +146,15 @@ int I411ToI420(const uint8* src_y, int src_stride_y,
                uint8* dst_u, int dst_stride_u,
                uint8* dst_v, int dst_stride_v,
                int width, int height) {
-  if (!src_y || !src_u || !src_v ||
-      !dst_y || !dst_u || !dst_v ||
-      width <= 0 || height == 0) {
-    return -1;
-  }
-  // Negative height means invert the image.
-  if (height < 0) {
-    height = -height;
-    src_y = src_y + (height - 1) * src_stride_y;
-    src_u = src_u + (height - 1) * src_stride_u;
-    src_v = src_v + (height - 1) * src_stride_v;
-    src_stride_y = -src_stride_y;
-    src_stride_u = -src_stride_u;
-    src_stride_v = -src_stride_v;
-  }
-
-  // Copy Y plane
-  if (dst_y) {
-    CopyPlane(src_y, src_stride_y, dst_y, dst_stride_y, width, height);
-  }
-
-  // Resample UV planes.
-  const int halfwidth = (width + 1) >> 1;
-  const int halfheight = (height + 1) >> 1;
-  const int quarterwidth = (width + 3) >> 2;
-  ScalePlane(src_u, src_stride_u, quarterwidth, height,
-             dst_u, dst_stride_u, halfwidth, halfheight,
-             kFilterNone);
-  ScalePlane(src_v, src_stride_v, quarterwidth, height,
-             dst_v, dst_stride_v, halfwidth, halfheight,
-             kFilterNone);
-  return 0;
+  const int src_uv_width = SUBSAMPLE(width, 3, 2);
+  return I4xxToI420(src_y, src_stride_y,
+                    src_u, src_stride_u,
+                    src_v, src_stride_v,
+                    dst_y, dst_stride_y,
+                    dst_u, dst_stride_u,
+                    dst_v, dst_stride_v,
+                    width, height,
+                    src_uv_width, height);
 }
 
 // I400 is greyscale typically used in MJPG
@@ -232,7 +200,6 @@ static void CopyPlane2(const uint8* src, int src_stride_0, int src_stride_1,
   }
 #endif
 #if defined(HAS_COPYROW_ERMS)
-  // TODO(fbarchard): Detect Fast String support.
   if (TestCpuFlag(kCpuHasERMS)) {
     CopyRow = CopyRow_ERMS;
   }
diff --git a/source/convert_from.cc b/source/convert_from.cc
index 0507150a9..dc708de5e 100644
--- a/source/convert_from.cc
+++ b/source/convert_from.cc
@@ -25,6 +25,40 @@ namespace libyuv {
 extern "C" {
 #endif
 
+#define SUBSAMPLE(v, a, s) (v < 0) ? (-((-v + a) >> s)) : ((v + a) >> s)
+static __inline int Abs(int v) {
+  return v >= 0 ? v : -v;
+}
+
+// I420 To any I4xx YUV format with mirroring.
+static int I420ToI4xx(const uint8* src_y, int src_stride_y,
+                      const uint8* src_u, int src_stride_u,
+                      const uint8* src_v, int src_stride_v,
+                      uint8* dst_y, int dst_stride_y,
+                      uint8* dst_u, int dst_stride_u,
+                      uint8* dst_v, int dst_stride_v,
+                      int src_y_width, int src_y_height,
+                      int dst_uv_width, int dst_uv_height) {
+  if (src_y_width == 0 || src_y_height == 0 ||
+      dst_uv_width <= 0 || dst_uv_height <= 0) {
+    return -1;
+  }
+  const int dst_y_width = Abs(src_y_width);
+  const int dst_y_height = Abs(src_y_height);
+  const int src_uv_width = SUBSAMPLE(src_y_width, 1, 1);
+  const int src_uv_height = SUBSAMPLE(src_y_height, 1, 1);
+  ScalePlane(src_y, src_stride_y, src_y_width, src_y_height,
+             dst_y, dst_stride_y, dst_y_width, dst_y_height,
+             kFilterBilinear);
+  ScalePlane(src_u, src_stride_u, src_uv_width, src_uv_height,
+             dst_u, dst_stride_u, dst_uv_width, dst_uv_height,
+             kFilterBilinear);
+  ScalePlane(src_v, src_stride_v, src_uv_width, src_uv_height,
+             dst_v, dst_stride_v, dst_uv_width, dst_uv_height,
+             kFilterBilinear);
+  return 0;
+}
+
 // 420 chroma is 1/2 width, 1/2 height
 // 422 chroma is 1/2 width, 1x height
 LIBYUV_API
@@ -35,38 +69,16 @@ int I420ToI422(const uint8* src_y, int src_stride_y,
                uint8* dst_u, int dst_stride_u,
                uint8* dst_v, int dst_stride_v,
                int width, int height) {
-  if (!src_y || !src_u || !src_v ||
-      !dst_y || !dst_u || !dst_v ||
-      width <= 0 || height == 0) {
-    return -1;
-  }
-  // Negative height means invert the image.
-  if (height < 0) {
-    height = -height;
-    dst_y = dst_y + (height - 1) * dst_stride_y;
-    dst_u = dst_u + (height - 1) * dst_stride_u;
-    dst_v = dst_v + (height - 1) * dst_stride_v;
-    dst_stride_y = -dst_stride_y;
-    dst_stride_u = -dst_stride_u;
-    dst_stride_v = -dst_stride_v;
-  }
-
-  // Copy Y plane.
-  // TODO(fbarchard): Scale Y plane, which will do a copy, but allows mirror.
-  if (dst_y) {
-    CopyPlane(src_y, src_stride_y, dst_y, dst_stride_y, width, height);
-  }
-
-  // Resample UV planes.
-  const int halfwidth = (width + 1) >> 1;
-  const int halfheight = (height + 1) >> 1;
-  ScalePlane(src_u, src_stride_u, halfwidth, halfheight,
-             dst_u, dst_stride_u, halfwidth, height,
-             kFilterBilinear);
-  ScalePlane(src_v, src_stride_v, halfwidth, halfheight,
-             dst_v, dst_stride_v, halfwidth, height,
-             kFilterBilinear);
-  return 0;
+  const int dst_uv_width = (Abs(width) + 1) >> 1;
+  const int dst_uv_height = Abs(height);
+  return I420ToI4xx(src_y, src_stride_y,
+                    src_u, src_stride_u,
+                    src_v, src_stride_v,
+                    dst_y, dst_stride_y,
+                    dst_u, dst_stride_u,
+                    dst_v, dst_stride_v,
+                    width, height,
+                    dst_uv_width, dst_uv_height);
 }
 
 // 420 chroma is 1/2 width, 1/2 height
@@ -79,37 +91,16 @@ int I420ToI444(const uint8* src_y, int src_stride_y,
                uint8* dst_u, int dst_stride_u,
                uint8* dst_v, int dst_stride_v,
                int width, int height) {
-  if (!src_y || !src_u|| !src_v ||
-      !dst_y || !dst_u || !dst_v ||
-      width <= 0 || height == 0) {
-    return -1;
-  }
-  // Negative height means invert the image.
-  if (height < 0) {
-    height = -height;
-    dst_y = dst_y + (height - 1) * dst_stride_y;
-    dst_u = dst_u + (height - 1) * dst_stride_u;
-    dst_v = dst_v + (height - 1) * dst_stride_v;
-    dst_stride_y = -dst_stride_y;
-    dst_stride_u = -dst_stride_u;
-    dst_stride_v = -dst_stride_v;
-  }
-
-  // Copy Y plane
-  if (dst_y) {
-    CopyPlane(src_y, src_stride_y, dst_y, dst_stride_y, width, height);
-  }
-
-  // Resample UV planes.
-  const int halfwidth = (width + 1) >> 1;
-  const int halfheight = (height + 1) >> 1;
-  ScalePlane(src_u, src_stride_u, halfwidth, halfheight,
-             dst_u, dst_stride_u, width, height,
-             kFilterBilinear);
-  ScalePlane(src_v, src_stride_v, halfwidth, halfheight,
-             dst_v, dst_stride_v, width, height,
-             kFilterBilinear);
-  return 0;
+  const int dst_uv_width = Abs(width);
+  const int dst_uv_height = Abs(height);
+  return I420ToI4xx(src_y, src_stride_y,
+                    src_u, src_stride_u,
+                    src_v, src_stride_v,
+                    dst_y, dst_stride_y,
+                    dst_u, dst_stride_u,
+                    dst_v, dst_stride_v,
+                    width, height,
+                    dst_uv_width, dst_uv_height);
 }
 
 // 420 chroma is 1/2 width, 1/2 height
@@ -122,38 +113,16 @@ int I420ToI411(const uint8* src_y, int src_stride_y,
                uint8* dst_u, int dst_stride_u,
                uint8* dst_v, int dst_stride_v,
                int width, int height) {
-  if (!src_y || !src_u || !src_v ||
-      !dst_y || !dst_u || !dst_v ||
-      width <= 0 || height == 0) {
-    return -1;
-  }
-  // Negative height means invert the image.
-  if (height < 0) {
-    height = -height;
-    dst_y = dst_y + (height - 1) * dst_stride_y;
-    dst_u = dst_u + (height - 1) * dst_stride_u;
-    dst_v = dst_v + (height - 1) * dst_stride_v;
-    dst_stride_y = -dst_stride_y;
-    dst_stride_u = -dst_stride_u;
-    dst_stride_v = -dst_stride_v;
-  }
-
-  // Copy Y plane
-  if (dst_y) {
-    CopyPlane(src_y, src_stride_y, dst_y, dst_stride_y, width, height);
-  }
-
-  // Resample UV planes.
-  const int halfwidth = (width + 1) >> 1;
-  const int halfheight = (height + 1) >> 1;
-  const int quarterwidth = (width + 3) >> 2;
-  ScalePlane(src_u, src_stride_u, halfwidth, halfheight,
-             dst_u, dst_stride_u, quarterwidth, height,
-             kFilterBilinear);
-  ScalePlane(src_v, src_stride_v, halfwidth, halfheight,
-             dst_v, dst_stride_v, quarterwidth, height,
-             kFilterBilinear);
-  return 0;
+  const int dst_uv_width = (Abs(width) + 3) >> 2;
+  const int dst_uv_height = Abs(height);
+  return I420ToI4xx(src_y, src_stride_y,
+                    src_u, src_stride_u,
+                    src_v, src_stride_v,
+                    dst_y, dst_stride_y,
+                    dst_u, dst_stride_u,
+                    dst_v, dst_stride_v,
+                    width, height,
+                    dst_uv_width, dst_uv_height);
 }
 
 // Copy to I400. Source can be I420,422,444,400,NV12,NV21
diff --git a/source/scale.cc b/source/scale.cc
index 893002ba7..0141e1cd6 100644
--- a/source/scale.cc
+++ b/source/scale.cc
@@ -30,10 +30,7 @@ static __inline int Abs(int v) {
   return v >= 0 ? v : -v;
 }
 
-static __inline int Half(int v) {
-  return v >= 0 ? ((v + 1) >> 1) : -((-v + 1) >> 1);
-}
-
+#define SUBSAMPLE(v, a, s) (v < 0) ? (-((-v + a) >> s)) : ((v + a) >> s)
 
 // Scale plane, 1/2
 // This is an optimized version for scaling down a plane to 1/2 of
@@ -763,8 +760,7 @@ static void ScalePlaneSimple(int src_width, int src_height,
 }
 
 // Scale a plane.
-// This function in turn calls a scaling function suitable for handling
-// the desired resolutions.
+// This function dispatches to a specialized scaler based on scale factor.
 
 LIBYUV_API
 void ScalePlane(const uint8* src, int src_stride,
@@ -772,6 +768,13 @@ void ScalePlane(const uint8* src, int src_stride,
                 uint8* dst, int dst_stride,
                 int dst_width, int dst_height,
                 FilterMode filtering) {
+  // Negative height means invert the image.
+  if (src_height < 0) {
+    src_height = -src_height;
+    src = src + (src_height - 1) * src_stride;
+    src_stride = -src_stride;
+  }
+
   // Use specialized scales to improve performance for common resolutions.
   // For example, all the 1/2 scalings will use ScalePlaneDown2()
   if (dst_width == src_width && dst_height == src_height) {
@@ -841,8 +844,6 @@ void ScalePlane(const uint8* src, int src_stride,
 
 // Scale an I420 image.
 // This function in turn calls a scaling function for each plane.
-// TODO(fbarchard): Disable UNDER_ALLOCATED_HACK
-#define UNDER_ALLOCATED_HACK 1
 
 LIBYUV_API
 int I420Scale(const uint8* src_y, int src_stride_y,
@@ -858,43 +859,10 @@ int I420Scale(const uint8* src_y, int src_stride_y,
       !dst_y || !dst_u || !dst_v || dst_width <= 0 || dst_height <= 0) {
     return -1;
   }
-  // Negative height means invert the image.
-  if (src_height < 0) {
-    src_height = -src_height;
-    int halfheight = Half(src_height);
-    src_y = src_y + (src_height - 1) * src_stride_y;
-    src_u = src_u + (halfheight - 1) * src_stride_u;
-    src_v = src_v + (halfheight - 1) * src_stride_v;
-    src_stride_y = -src_stride_y;
-    src_stride_u = -src_stride_u;
-    src_stride_v = -src_stride_v;
-  }
-  int src_halfwidth = Half(src_width);
-  int src_halfheight = Half(src_height);
-  int dst_halfwidth = Half(dst_width);
-  int dst_halfheight = Half(dst_height);
-
-#ifdef UNDER_ALLOCATED_HACK
-  // If caller passed width / 2 for stride, adjust halfwidth to match.
-  if ((src_width & 1) && src_stride_u && src_halfwidth > Abs(src_stride_u)) {
-    src_halfwidth = src_width >> 1;
-  }
-  if ((dst_width & 1) && dst_stride_u && dst_halfwidth > Abs(dst_stride_u)) {
-    dst_halfwidth = dst_width >> 1;
-  }
-  // If caller used height / 2 when computing src_v, it will point into what
-  // should be the src_u plane. Detect this and reduce halfheight to match.
-  int uv_src_plane_size = src_halfwidth * src_halfheight;
-  if ((src_height & 1) &&
-      (src_v > src_u) && (src_v < (src_u + uv_src_plane_size))) {
-    src_halfheight = src_height >> 1;
-  }
-  int uv_dst_plane_size = dst_halfwidth * dst_halfheight;
-  if ((dst_height & 1) &&
-      (dst_v > dst_u) && (dst_v < (dst_u + uv_dst_plane_size))) {
-    dst_halfheight = dst_height >> 1;
-  }
-#endif
+  int src_halfwidth = SUBSAMPLE(src_width, 1, 1);
+  int src_halfheight = SUBSAMPLE(src_height, 1, 1);
+  int dst_halfwidth = SUBSAMPLE(dst_width, 1, 1);
+  int dst_halfheight = SUBSAMPLE(dst_height, 1, 1);
 
   ScalePlane(src_y, src_stride_y, src_width, src_height,
              dst_y, dst_stride_y, dst_width, dst_height,
@@ -917,59 +885,15 @@ int Scale(const uint8* src_y, const uint8* src_u, const uint8* src_v,
           int dst_stride_y, int dst_stride_u, int dst_stride_v,
           int dst_width, int dst_height,
           bool interpolate) {
-  if (!src_y || !src_u || !src_v || src_width <= 0 || src_height == 0 ||
-      !dst_y || !dst_u || !dst_v || dst_width <= 0 || dst_height <= 0) {
-    return -1;
-  }
-  // Negative height means invert the image.
-  if (src_height < 0) {
-    src_height = -src_height;
-    int halfheight = Half(src_height);
-    src_y = src_y + (src_height - 1) * src_stride_y;
-    src_u = src_u + (halfheight - 1) * src_stride_u;
-    src_v = src_v + (halfheight - 1) * src_stride_v;
-    src_stride_y = -src_stride_y;
-    src_stride_u = -src_stride_u;
-    src_stride_v = -src_stride_v;
-  }
-  int src_halfwidth = Half(src_width);
-  int src_halfheight = Half(src_height);
-  int dst_halfwidth = Half(dst_width);
-  int dst_halfheight = Half(dst_height);
-  FilterMode filtering = interpolate ? kFilterBox : kFilterNone;
-
-#ifdef UNDER_ALLOCATED_HACK
-  // If caller passed width / 2 for stride, adjust halfwidth to match.
-  if ((src_width & 1) && src_stride_u && src_halfwidth > Abs(src_stride_u)) {
-    src_halfwidth = src_width >> 1;
-  }
-  if ((dst_width & 1) && dst_stride_u && dst_halfwidth > Abs(dst_stride_u)) {
-    dst_halfwidth = dst_width >> 1;
-  }
-  // If caller used height / 2 when computing src_v, it will point into what
-  // should be the src_u plane. Detect this and reduce halfheight to match.
-  int uv_src_plane_size = src_halfwidth * src_halfheight;
-  if ((src_height & 1) &&
-      (src_v > src_u) && (src_v < (src_u + uv_src_plane_size))) {
-    src_halfheight = src_height >> 1;
-  }
-  int uv_dst_plane_size = dst_halfwidth * dst_halfheight;
-  if ((dst_height & 1) &&
-      (dst_v > dst_u) && (dst_v < (dst_u + uv_dst_plane_size))) {
-    dst_halfheight = dst_height >> 1;
-  }
-#endif
-
-  ScalePlane(src_y, src_stride_y, src_width, src_height,
-             dst_y, dst_stride_y, dst_width, dst_height,
-             filtering);
-  ScalePlane(src_u, src_stride_u, src_halfwidth, src_halfheight,
-             dst_u, dst_stride_u, dst_halfwidth, dst_halfheight,
-             filtering);
-  ScalePlane(src_v, src_stride_v, src_halfwidth, src_halfheight,
-             dst_v, dst_stride_v, dst_halfwidth, dst_halfheight,
-             filtering);
-  return 0;
+  return I420Scale(src_y, src_stride_y,
+                   src_u, src_stride_u,
+                   src_v, src_stride_v,
+                   src_width, src_height,
+                   dst_y, dst_stride_y,
+                   dst_u, dst_stride_u,
+                   dst_v, dst_stride_v,
+                   dst_width, dst_height,
+                   interpolate ? kFilterBox : kFilterNone);
 }
 
 // Deprecated api
@@ -983,10 +907,10 @@ int ScaleOffset(const uint8* src, int src_width, int src_height,
     return -1;
   }
   dst_yoffset = dst_yoffset & ~1;  // chroma requires offset to multiple of 2.
-  int src_halfwidth = Half(src_width);
-  int src_halfheight = Half(src_height);
-  int dst_halfwidth = Half(dst_width);
-  int dst_halfheight = Half(dst_height);
+  int src_halfwidth = SUBSAMPLE(src_width, 1, 1);
+  int src_halfheight = SUBSAMPLE(src_height, 1, 1);
+  int dst_halfwidth = SUBSAMPLE(dst_width, 1, 1);
+  int dst_halfheight = SUBSAMPLE(dst_height, 1, 1);
   int aheight = dst_height - dst_yoffset * 2;  // actual output height
   const uint8* src_y = src;
   const uint8* src_u = src + src_width * src_height;
@@ -997,9 +921,15 @@ int ScaleOffset(const uint8* src, int src_width, int src_height,
                  (dst_yoffset >> 1) * dst_halfwidth;
   uint8* dst_v = dst + dst_width * dst_height + dst_halfwidth * dst_halfheight +
                  (dst_yoffset >> 1) * dst_halfwidth;
-  return Scale(src_y, src_u, src_v, src_width, src_halfwidth, src_halfwidth,
-               src_width, src_height, dst_y, dst_u, dst_v, dst_width,
-               dst_halfwidth, dst_halfwidth, dst_width, aheight, interpolate);
+  return I420Scale(src_y, src_width,
+                   src_u, src_halfwidth,
+                   src_v, src_halfwidth,
+                   src_width, src_height,
+                   dst_y, dst_width,
+                   dst_u, dst_halfwidth,
+                   dst_v, dst_halfwidth,
+                   dst_width, aheight,
+                   interpolate ? kFilterBox : kFilterNone);
 }
 
 #ifdef __cplusplus
diff --git a/source/scale_common.cc b/source/scale_common.cc
index a4a9e3ef6..e7f56d319 100644
--- a/source/scale_common.cc
+++ b/source/scale_common.cc
@@ -462,7 +462,7 @@ void ScalePlaneVertical(int src_height,
                         int bpp, FilterMode filtering) {
   int dst_widthx4 = dst_width * bpp;
   src_argb += (x >> 16) * bpp;
-  assert(src_height > 0);
+  assert(src_height != 0);
   assert(dst_width > 0);
   assert(dst_height > 0);
   void (*InterpolateRow)(uint8* dst_argb, const uint8* src_argb,