Add m-esr52 at 52.6.0

1 files changed, 672 insertions, 0 deletions

diff --git a/gfx/ycbcr/ycbcr_to_rgb565.cpp b/gfx/ycbcr/ycbcr_to_rgb565.cpp
new file mode 100644
index 000000000..0572e3e09
--- /dev/null
+++ b/gfx/ycbcr/ycbcr_to_rgb565.cpp
@@ -0,0 +1,672 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <stdlib.h>
+#include <limits.h>
+#include "nsDebug.h"
+#include "ycbcr_to_rgb565.h"
+#include "nsAlgorithm.h"
+
+
+
+#ifdef HAVE_YCBCR_TO_RGB565
+
+namespace mozilla {
+
+namespace gfx {
+
+/*This contains all of the parameters that are needed to convert a row.
+  Passing them in a struct instead of as individual parameters saves the need
+   to continually push onto the stack the ones that are fixed for every row.*/
+struct yuv2rgb565_row_scale_bilinear_ctx{
+  uint16_t *rgb_row;
+  const uint8_t *y_row;
+  const uint8_t *u_row;
+  const uint8_t *v_row;
+  int y_yweight;
+  int y_pitch;
+  int width;
+  int source_x0_q16;
+  int source_dx_q16;
+  /*Not used for 4:4:4, except with chroma-nearest.*/
+  int source_uv_xoffs_q16;
+  /*Not used for 4:4:4 or chroma-nearest.*/
+  int uv_pitch;
+  /*Not used for 4:2:2, 4:4:4, or chroma-nearest.*/
+  int uv_yweight;
+};
+
+
+
+/*This contains all of the parameters that are needed to convert a row.
+  Passing them in a struct instead of as individual parameters saves the need
+   to continually push onto the stack the ones that are fixed for every row.*/
+struct yuv2rgb565_row_scale_nearest_ctx{
+  uint16_t *rgb_row;
+  const uint8_t *y_row;
+  const uint8_t *u_row;
+  const uint8_t *v_row;
+  int width;
+  int source_x0_q16;
+  int source_dx_q16;
+  /*Not used for 4:4:4.*/
+  int source_uv_xoffs_q16;
+};
+
+
+
+typedef void (*yuv2rgb565_row_scale_bilinear_func)(
+ const yuv2rgb565_row_scale_bilinear_ctx *ctx, int dither);
+
+typedef void (*yuv2rgb565_row_scale_nearest_func)(
+ const yuv2rgb565_row_scale_nearest_ctx *ctx, int dither);
+
+
+
+//TODO: fix NEON asm for iOS
+# if defined(MOZILLA_MAY_SUPPORT_NEON) && !defined(__APPLE__)
+
+extern "C" void ScaleYCbCr42xToRGB565_BilinearY_Row_NEON(
+ const yuv2rgb565_row_scale_bilinear_ctx *ctx, int dither);
+
+void __attribute((noinline)) yuv42x_to_rgb565_row_neon(uint16 *dst,
+                                                       const uint8 *y,
+                                                       const uint8 *u,
+                                                       const uint8 *v,
+                                                       int n,
+                                                       int oddflag);
+
+#endif
+
+
+
+/*Bilinear interpolation of a single value.
+  This uses the exact same formulas as the asm, even though it adds some extra
+   shifts that do nothing but reduce accuracy.*/
+static int bislerp(const uint8_t *row,
+                   int pitch,
+                   int source_x,
+                   int xweight,
+                   int yweight) {
+  int a;
+  int b;
+  int c;
+  int d;
+  a = row[source_x];
+  b = row[source_x+1];
+  c = row[source_x+pitch];
+  d = row[source_x+pitch+1];
+  a = ((a<<8)+(c-a)*yweight+128)>>8;
+  b = ((b<<8)+(d-b)*yweight+128)>>8;
+  return ((a<<8)+(b-a)*xweight+128)>>8;
+}
+
+/*Convert a single pixel from Y'CbCr to RGB565.
+  This uses the exact same formulas as the asm, even though we could make the
+   constants a lot more accurate with 32-bit wide registers.*/
+static uint16_t yu2rgb565(int y, int u, int v, int dither) {
+  /*This combines the constant offset that needs to be added during the Y'CbCr
+     conversion with a rounding offset that depends on the dither parameter.*/
+  static const int DITHER_BIAS[4][3]={
+    {-14240,    8704,    -17696},
+    {-14240+128,8704+64, -17696+128},
+    {-14240+256,8704+128,-17696+256},
+    {-14240+384,8704+192,-17696+384}
+  };
+  int r;
+  int g;
+  int b;
+  r = clamped((74*y+102*v+DITHER_BIAS[dither][0])>>9, 0, 31);
+  g = clamped((74*y-25*u-52*v+DITHER_BIAS[dither][1])>>8, 0, 63);
+  b = clamped((74*y+129*u+DITHER_BIAS[dither][2])>>9, 0, 31);
+  return (uint16_t)(r<<11 | g<<5 | b);
+}
+
+static void ScaleYCbCr420ToRGB565_Bilinear_Row_C(
+ const yuv2rgb565_row_scale_bilinear_ctx *ctx, int dither){
+  int x;
+  int source_x_q16;
+  source_x_q16 = ctx->source_x0_q16;
+  for (x = 0; x < ctx->width; x++) {
+    int source_x;
+    int xweight;
+    int y;
+    int u;
+    int v;
+    xweight = ((source_x_q16&0xFFFF)+128)>>8;
+    source_x = source_x_q16>>16;
+    y = bislerp(ctx->y_row, ctx->y_pitch, source_x, xweight, ctx->y_yweight);
+    xweight = (((source_x_q16+ctx->source_uv_xoffs_q16)&0x1FFFF)+256)>>9;
+    source_x = (source_x_q16+ctx->source_uv_xoffs_q16)>>17;
+    source_x_q16 += ctx->source_dx_q16;
+    u = bislerp(ctx->u_row, ctx->uv_pitch, source_x, xweight, ctx->uv_yweight);
+    v = bislerp(ctx->v_row, ctx->uv_pitch, source_x, xweight, ctx->uv_yweight);
+    ctx->rgb_row[x] = yu2rgb565(y, u, v, dither);
+    dither ^= 3;
+  }
+}
+
+static void ScaleYCbCr422ToRGB565_Bilinear_Row_C(
+ const yuv2rgb565_row_scale_bilinear_ctx *ctx, int dither){
+  int x;
+  int source_x_q16;
+  source_x_q16 = ctx->source_x0_q16;
+  for (x = 0; x < ctx->width; x++) {
+    int source_x;
+    int xweight;
+    int y;
+    int u;
+    int v;
+    xweight = ((source_x_q16&0xFFFF)+128)>>8;
+    source_x = source_x_q16>>16;
+    y = bislerp(ctx->y_row, ctx->y_pitch, source_x, xweight, ctx->y_yweight);
+    xweight = (((source_x_q16+ctx->source_uv_xoffs_q16)&0x1FFFF)+256)>>9;
+    source_x = (source_x_q16+ctx->source_uv_xoffs_q16)>>17;
+    source_x_q16 += ctx->source_dx_q16;
+    u = bislerp(ctx->u_row, ctx->uv_pitch, source_x, xweight, ctx->y_yweight);
+    v = bislerp(ctx->v_row, ctx->uv_pitch, source_x, xweight, ctx->y_yweight);
+    ctx->rgb_row[x] = yu2rgb565(y, u, v, dither);
+    dither ^= 3;
+  }
+}
+
+static void ScaleYCbCr444ToRGB565_Bilinear_Row_C(
+ const yuv2rgb565_row_scale_bilinear_ctx *ctx, int dither){
+  int x;
+  int source_x_q16;
+  source_x_q16 = ctx->source_x0_q16;
+  for (x = 0; x < ctx->width; x++) {
+    int source_x;
+    int xweight;
+    int y;
+    int u;
+    int v;
+    xweight = ((source_x_q16&0xFFFF)+128)>>8;
+    source_x = source_x_q16>>16;
+    source_x_q16 += ctx->source_dx_q16;
+    y = bislerp(ctx->y_row, ctx->y_pitch, source_x, xweight, ctx->y_yweight);
+    u = bislerp(ctx->u_row, ctx->y_pitch, source_x, xweight, ctx->y_yweight);
+    v = bislerp(ctx->v_row, ctx->y_pitch, source_x, xweight, ctx->y_yweight);
+    ctx->rgb_row[x] = yu2rgb565(y, u, v, dither);
+    dither ^= 3;
+  }
+}
+
+static void ScaleYCbCr42xToRGB565_BilinearY_Row_C(
+ const yuv2rgb565_row_scale_bilinear_ctx *ctx, int dither){
+  int x;
+  int source_x_q16;
+  source_x_q16 = ctx->source_x0_q16;
+  for (x = 0; x < ctx->width; x++) {
+    int source_x;
+    int xweight;
+    int y;
+    int u;
+    int v;
+    xweight = ((source_x_q16&0xFFFF)+128)>>8;
+    source_x = source_x_q16>>16;
+    y = bislerp(ctx->y_row, ctx->y_pitch, source_x, xweight, ctx->y_yweight);
+    source_x = (source_x_q16+ctx->source_uv_xoffs_q16)>>17;
+    source_x_q16 += ctx->source_dx_q16;
+    u = ctx->u_row[source_x];
+    v = ctx->v_row[source_x];
+    ctx->rgb_row[x] = yu2rgb565(y, u, v, dither);
+    dither ^= 3;
+  }
+}
+
+static void ScaleYCbCr444ToRGB565_BilinearY_Row_C(
+ const yuv2rgb565_row_scale_bilinear_ctx *ctx, int dither){
+  int x;
+  int source_x_q16;
+  source_x_q16 = ctx->source_x0_q16;
+  for (x = 0; x < ctx->width; x++) {
+    int source_x;
+    int xweight;
+    int y;
+    int u;
+    int v;
+    xweight = ((source_x_q16&0xFFFF)+128)>>8;
+    source_x = source_x_q16>>16;
+    y = bislerp(ctx->y_row, ctx->y_pitch, source_x, xweight, ctx->y_yweight);
+    source_x = (source_x_q16+ctx->source_uv_xoffs_q16)>>16;
+    source_x_q16 += ctx->source_dx_q16;
+    u = ctx->u_row[source_x];
+    v = ctx->v_row[source_x];
+    ctx->rgb_row[x] = yu2rgb565(y, u, v, dither);
+    dither ^= 3;
+  }
+}
+
+static void ScaleYCbCr42xToRGB565_Nearest_Row_C(
+ const yuv2rgb565_row_scale_nearest_ctx *ctx, int dither){
+  int y;
+  int u;
+  int v;
+  int x;
+  int source_x_q16;
+  int source_x;
+  source_x_q16 = ctx->source_x0_q16;
+  for (x = 0; x < ctx->width; x++) {
+    source_x = source_x_q16>>16;
+    y = ctx->y_row[source_x];
+    source_x = (source_x_q16+ctx->source_uv_xoffs_q16)>>17;
+    source_x_q16 += ctx->source_dx_q16;
+    u = ctx->u_row[source_x];
+    v = ctx->v_row[source_x];
+    ctx->rgb_row[x] = yu2rgb565(y, u, v, dither);
+    dither ^= 3;
+  }
+}
+
+static void ScaleYCbCr444ToRGB565_Nearest_Row_C(
+ const yuv2rgb565_row_scale_nearest_ctx *ctx, int dither){
+  int y;
+  int u;
+  int v;
+  int x;
+  int source_x_q16;
+  int source_x;
+  source_x_q16 = ctx->source_x0_q16;
+  for (x = 0; x < ctx->width; x++) {
+    source_x = source_x_q16>>16;
+    source_x_q16 += ctx->source_dx_q16;
+    y = ctx->y_row[source_x];
+    u = ctx->u_row[source_x];
+    v = ctx->v_row[source_x];
+    ctx->rgb_row[x] = yu2rgb565(y, u, v, dither);
+    dither ^= 3;
+  }
+}
+
+void ScaleYCbCrToRGB565(const uint8_t *y_buf,
+                                 const uint8_t *u_buf,
+                                 const uint8_t *v_buf,
+                                 uint8_t *rgb_buf,
+                                 int source_x0,
+                                 int source_y0,
+                                 int source_width,
+                                 int source_height,
+                                 int width,
+                                 int height,
+                                 int y_pitch,
+                                 int uv_pitch,
+                                 int rgb_pitch,
+                                 YUVType yuv_type,
+                                 ScaleFilter filter) {
+  int source_x0_q16;
+  int source_y0_q16;
+  int source_dx_q16;
+  int source_dy_q16;
+  int source_uv_xoffs_q16;
+  int source_uv_yoffs_q16;
+  int x_shift;
+  int y_shift;
+  int ymin;
+  int ymax;
+  int uvmin;
+  int uvmax;
+  int dither;
+  /*We don't support negative destination rectangles (just flip the source
+     instead), and for empty ones there's nothing to do.*/
+  if (width <= 0 || height <= 0)
+    return;
+  /*These bounds are required to avoid 16.16 fixed-point overflow.*/
+  NS_ASSERTION(source_x0 > (INT_MIN>>16) && source_x0 < (INT_MAX>>16),
+    "ScaleYCbCrToRGB565 source X offset out of bounds.");
+  NS_ASSERTION(source_x0+source_width > (INT_MIN>>16)
+            && source_x0+source_width < (INT_MAX>>16),
+    "ScaleYCbCrToRGB565 source width out of bounds.");
+  NS_ASSERTION(source_y0 > (INT_MIN>>16) && source_y0 < (INT_MAX>>16),
+    "ScaleYCbCrToRGB565 source Y offset out of bounds.");
+  NS_ASSERTION(source_y0+source_height > (INT_MIN>>16)
+            && source_y0+source_height < (INT_MAX>>16),
+    "ScaleYCbCrToRGB565 source height out of bounds.");
+  /*We require the same stride for Y' and Cb and Cr for 4:4:4 content.*/
+  NS_ASSERTION(yuv_type != YV24 || y_pitch == uv_pitch,
+    "ScaleYCbCrToRGB565 luma stride differs from chroma for 4:4:4 content.");
+  /*We assume we can read outside the bounds of the input, because it makes
+     the code much simpler (and in practice is true: both Theora and VP8 return
+     padded reference frames).
+    In practice, we do not even _have_ the actual bounds of the source, as
+     we are passed a crop rectangle from it, and not the dimensions of the full
+     image.
+    This assertion will not guarantee our out-of-bounds reads are safe, but it
+     should at least catch the simple case of passing in an unpadded buffer.*/
+  NS_ASSERTION(abs(y_pitch) >= abs(source_width)+16,
+    "ScaleYCbCrToRGB565 source image unpadded?");
+  /*The NEON code requires the pointers to be aligned to a 16-byte boundary at
+     the start of each row.
+    This should be true for all of our sources.
+    We could try to fix this up if it's not true by adjusting source_x0, but
+     that would require the mis-alignment to be the same for the U and V
+     planes.*/
+  NS_ASSERTION((y_pitch&15) == 0 && (uv_pitch&15) == 0 &&
+   ((y_buf-(uint8_t *)nullptr)&15) == 0 &&
+   ((u_buf-(uint8_t *)nullptr)&15) == 0 &&
+   ((v_buf-(uint8_t *)nullptr)&15) == 0,
+   "ScaleYCbCrToRGB565 source image unaligned");
+  /*We take an area-based approach to pixel coverage to avoid shifting by small
+     amounts (or not so small, when up-scaling or down-scaling by a large
+     factor).
+
+    An illustrative example: scaling 4:2:0 up by 2, using JPEG chroma cositing^.
+
+    + = RGB destination locations
+    * = Y' source locations
+    - = Cb, Cr source locations
+
+    +   +   +   +  +   +   +   +
+      *       *      *       *
+    +   +   +   +  +   +   +   +
+          -              -
+    +   +   +   +  +   +   +   +
+      *       *      *       *
+    +   +   +   +  +   +   +   +
+
+    +   +   +   +  +   +   +   +
+      *       *      *       *
+    +   +   +   +  +   +   +   +
+          -              -
+    +   +   +   +  +   +   +   +
+      *       *      *       *
+    +   +   +   +  +   +   +   +
+
+    So, the coordinates of the upper-left + (first destination site) should
+     be (-0.25,-0.25) in the source Y' coordinate system.
+    Similarly, the coordinates should be (-0.375,-0.375) in the source Cb, Cr
+     coordinate system.
+    Note that the origin and scale of these two coordinate systems is not the
+     same!
+
+    ^JPEG cositing is required for Theora; VP8 doesn't specify cositing rules,
+     but nearly all software converters in existence (at least those that are
+     open source, and many that are not) use JPEG cositing instead of MPEG.*/
+  source_dx_q16 = (source_width<<16) / width;
+  source_x0_q16 = (source_x0<<16)+(source_dx_q16>>1)-0x8000;
+  source_dy_q16 = (source_height<<16) / height;
+  source_y0_q16 = (source_y0<<16)+(source_dy_q16>>1)-0x8000;
+  x_shift = (yuv_type != YV24);
+  y_shift = (yuv_type == YV12);
+  /*These two variables hold the difference between the origins of the Y' and
+     the Cb, Cr coordinate systems, using the scale of the Y' coordinate
+     system.*/
+  source_uv_xoffs_q16 = -(x_shift<<15);
+  source_uv_yoffs_q16 = -(y_shift<<15);
+  /*Compute the range of source rows we'll actually use.
+    This doesn't guarantee we won't read outside this range.*/
+  ymin = source_height >= 0 ? source_y0 : source_y0+source_height-1;
+  ymax = source_height >= 0 ? source_y0+source_height-1 : source_y0;
+  uvmin = ymin>>y_shift;
+  uvmax = ((ymax+1+y_shift)>>y_shift)-1;
+  /*Pick a dithering pattern.
+    The "&3" at the end is just in case RAND_MAX is lying.*/
+  dither = (rand()/(RAND_MAX>>2))&3;
+  /*Nearest-neighbor scaling.*/
+  if (filter == FILTER_NONE) {
+    yuv2rgb565_row_scale_nearest_ctx ctx;
+    yuv2rgb565_row_scale_nearest_func scale_row;
+    int y;
+    /*Add rounding offsets once, in advance.*/
+    source_x0_q16 += 0x8000;
+    source_y0_q16 += 0x8000;
+    source_uv_xoffs_q16 += (x_shift<<15);
+    source_uv_yoffs_q16 += (y_shift<<15);
+    if (yuv_type == YV12)
+      scale_row = ScaleYCbCr42xToRGB565_Nearest_Row_C;
+    else
+      scale_row = ScaleYCbCr444ToRGB565_Nearest_Row_C;
+    ctx.width = width;
+    ctx.source_x0_q16 = source_x0_q16;
+    ctx.source_dx_q16 = source_dx_q16;
+    ctx.source_uv_xoffs_q16 = source_uv_xoffs_q16;
+    for (y=0; y<height; y++) {
+      int source_y;
+      ctx.rgb_row = (uint16_t *)(rgb_buf + y*rgb_pitch);
+      source_y = source_y0_q16>>16;
+      source_y = clamped(source_y, ymin, ymax);
+      ctx.y_row = y_buf + source_y*y_pitch;
+      source_y = (source_y0_q16+source_uv_yoffs_q16)>>(16+y_shift);
+      source_y = clamped(source_y, uvmin, uvmax);
+      source_y0_q16 += source_dy_q16;
+      ctx.u_row = u_buf + source_y*uv_pitch;
+      ctx.v_row = v_buf + source_y*uv_pitch;
+      (*scale_row)(&ctx, dither);
+      dither ^= 2;
+    }
+  }
+  /*Bilinear scaling.*/
+  else {
+    yuv2rgb565_row_scale_bilinear_ctx ctx;
+    yuv2rgb565_row_scale_bilinear_func scale_row;
+    int uvxscale_min;
+    int uvxscale_max;
+    int uvyscale_min;
+    int uvyscale_max;
+    int y;
+    /*Check how close the chroma scaling is to unity.
+      If it's close enough, we can get away with nearest-neighbor chroma
+       sub-sampling, and only doing bilinear on luma.
+      If a given axis is subsampled, we use bounds on the luma step of
+       [0.67...2], which is equivalent to scaling chroma by [1...3].
+      If it's not subsampled, we use bounds of [0.5...1.33], which is
+       equivalent to scaling chroma by [0.75...2].
+      The lower bound is chosen as a trade-off between speed and how terrible
+       nearest neighbor looks when upscaling.*/
+# define CHROMA_NEAREST_SUBSAMP_STEP_MIN  0xAAAA
+# define CHROMA_NEAREST_NORMAL_STEP_MIN   0x8000
+# define CHROMA_NEAREST_SUBSAMP_STEP_MAX 0x20000
+# define CHROMA_NEAREST_NORMAL_STEP_MAX  0x15555
+    uvxscale_min = yuv_type != YV24 ?
+     CHROMA_NEAREST_SUBSAMP_STEP_MIN : CHROMA_NEAREST_NORMAL_STEP_MIN;
+    uvxscale_max = yuv_type != YV24 ?
+     CHROMA_NEAREST_SUBSAMP_STEP_MAX : CHROMA_NEAREST_NORMAL_STEP_MAX;
+    uvyscale_min = yuv_type == YV12 ?
+     CHROMA_NEAREST_SUBSAMP_STEP_MIN : CHROMA_NEAREST_NORMAL_STEP_MIN;
+    uvyscale_max = yuv_type == YV12 ?
+     CHROMA_NEAREST_SUBSAMP_STEP_MAX : CHROMA_NEAREST_NORMAL_STEP_MAX;
+    if (uvxscale_min <= abs(source_dx_q16)
+     && abs(source_dx_q16) <= uvxscale_max
+     && uvyscale_min <= abs(source_dy_q16)
+     && abs(source_dy_q16) <= uvyscale_max) {
+      /*Add the rounding offsets now.*/
+      source_uv_xoffs_q16 += 1<<(15+x_shift);
+      source_uv_yoffs_q16 += 1<<(15+y_shift);
+      if (yuv_type != YV24) {
+        scale_row =
+//TODO: fix NEON asm for iOS
+#  if defined(MOZILLA_MAY_SUPPORT_NEON) && !defined(__APPLE__)
+         supports_neon() ? ScaleYCbCr42xToRGB565_BilinearY_Row_NEON :
+#  endif
+         ScaleYCbCr42xToRGB565_BilinearY_Row_C;
+      }
+      else
+        scale_row = ScaleYCbCr444ToRGB565_BilinearY_Row_C;
+    }
+    else {
+      if (yuv_type == YV12)
+        scale_row = ScaleYCbCr420ToRGB565_Bilinear_Row_C;
+      else if (yuv_type == YV16)
+        scale_row = ScaleYCbCr422ToRGB565_Bilinear_Row_C;
+      else
+        scale_row = ScaleYCbCr444ToRGB565_Bilinear_Row_C;
+    }
+    ctx.width = width;
+    ctx.y_pitch = y_pitch;
+    ctx.source_x0_q16 = source_x0_q16;
+    ctx.source_dx_q16 = source_dx_q16;
+    ctx.source_uv_xoffs_q16 = source_uv_xoffs_q16;
+    ctx.uv_pitch = uv_pitch;
+    for (y=0; y<height; y++) {
+      int source_y;
+      int yweight;
+      int uvweight;
+      ctx.rgb_row = (uint16_t *)(rgb_buf + y*rgb_pitch);
+      source_y = (source_y0_q16+128)>>16;
+      yweight = ((source_y0_q16+128)>>8)&0xFF;
+      if (source_y < ymin) {
+        source_y = ymin;
+        yweight = 0;
+      }
+      if (source_y > ymax) {
+        source_y = ymax;
+        yweight = 0;
+      }
+      ctx.y_row = y_buf + source_y*y_pitch;
+      source_y = source_y0_q16+source_uv_yoffs_q16+(128<<y_shift);
+      source_y0_q16 += source_dy_q16;
+      uvweight = source_y>>(8+y_shift)&0xFF;
+      source_y >>= 16+y_shift;
+      if (source_y < uvmin) {
+        source_y = uvmin;
+        uvweight = 0;
+      }
+      if (source_y > uvmax) {
+        source_y = uvmax;
+        uvweight = 0;
+      }
+      ctx.u_row = u_buf + source_y*uv_pitch;
+      ctx.v_row = v_buf + source_y*uv_pitch;
+      ctx.y_yweight = yweight;
+      ctx.uv_yweight = uvweight;
+      (*scale_row)(&ctx, dither);
+      dither ^= 2;
+    }
+  }
+}
+
+bool IsScaleYCbCrToRGB565Fast(int source_x0,
+                                       int source_y0,
+                                       int source_width,
+                                       int source_height,
+                                       int width,
+                                       int height,
+                                       YUVType yuv_type,
+                                       ScaleFilter filter)
+{
+  // Very fast.
+  if (width <= 0 || height <= 0)
+    return true;
+#  if defined(MOZILLA_MAY_SUPPORT_NEON)
+  if (filter != FILTER_NONE) {
+    int source_dx_q16;
+    int source_dy_q16;
+    int uvxscale_min;
+    int uvxscale_max;
+    int uvyscale_min;
+    int uvyscale_max;
+    source_dx_q16 = (source_width<<16) / width;
+    source_dy_q16 = (source_height<<16) / height;
+    uvxscale_min = yuv_type != YV24 ?
+     CHROMA_NEAREST_SUBSAMP_STEP_MIN : CHROMA_NEAREST_NORMAL_STEP_MIN;
+    uvxscale_max = yuv_type != YV24 ?
+     CHROMA_NEAREST_SUBSAMP_STEP_MAX : CHROMA_NEAREST_NORMAL_STEP_MAX;
+    uvyscale_min = yuv_type == YV12 ?
+     CHROMA_NEAREST_SUBSAMP_STEP_MIN : CHROMA_NEAREST_NORMAL_STEP_MIN;
+    uvyscale_max = yuv_type == YV12 ?
+     CHROMA_NEAREST_SUBSAMP_STEP_MAX : CHROMA_NEAREST_NORMAL_STEP_MAX;
+    if (uvxscale_min <= abs(source_dx_q16)
+     && abs(source_dx_q16) <= uvxscale_max
+     && uvyscale_min <= abs(source_dy_q16)
+     && abs(source_dy_q16) <= uvyscale_max) {
+      if (yuv_type != YV24)
+        return supports_neon();
+    }
+  }
+#  endif
+  return false;
+}
+
+
+
+void yuv_to_rgb565_row_c(uint16 *dst,
+                         const uint8 *y,
+                         const uint8 *u,
+                         const uint8 *v,
+                         int x_shift,
+                         int pic_x,
+                         int pic_width)
+{
+  int x;
+  for (x = 0; x < pic_width; x++)
+  {
+    dst[x] = yu2rgb565(y[pic_x+x],
+                       u[(pic_x+x)>>x_shift],
+                       v[(pic_x+x)>>x_shift],
+                       2); // Disable dithering for now.
+  }
+}
+
+void ConvertYCbCrToRGB565(const uint8* y_buf,
+                                   const uint8* u_buf,
+                                   const uint8* v_buf,
+                                   uint8* rgb_buf,
+                                   int pic_x,
+                                   int pic_y,
+                                   int pic_width,
+                                   int pic_height,
+                                   int y_pitch,
+                                   int uv_pitch,
+                                   int rgb_pitch,
+                                   YUVType yuv_type)
+{
+  int x_shift;
+  int y_shift;
+  x_shift = yuv_type != YV24;
+  y_shift = yuv_type == YV12;
+//TODO: fix NEON asm for iOS
+#  if defined(MOZILLA_MAY_SUPPORT_NEON) && !defined(__APPLE__)
+  if (yuv_type != YV24 && supports_neon())
+  {
+    for (int i = 0; i < pic_height; i++) {
+      int yoffs;
+      int uvoffs;
+      yoffs = y_pitch * (pic_y+i) + pic_x;
+      uvoffs = uv_pitch * ((pic_y+i)>>y_shift) + (pic_x>>x_shift);
+      yuv42x_to_rgb565_row_neon((uint16*)(rgb_buf + rgb_pitch * i),
+                                y_buf + yoffs,
+                                u_buf + uvoffs,
+                                v_buf + uvoffs,
+                                pic_width,
+                                pic_x&x_shift);
+    }
+  }
+  else
+#  endif
+  {
+    for (int i = 0; i < pic_height; i++) {
+      int yoffs;
+      int uvoffs;
+      yoffs = y_pitch * (pic_y+i);
+      uvoffs = uv_pitch * ((pic_y+i)>>y_shift);
+      yuv_to_rgb565_row_c((uint16*)(rgb_buf + rgb_pitch * i),
+                          y_buf + yoffs,
+                          u_buf + uvoffs,
+                          v_buf + uvoffs,
+                          x_shift,
+                          pic_x,
+                          pic_width);
+    }
+  }
+}
+
+bool IsConvertYCbCrToRGB565Fast(int pic_x,
+                                         int pic_y,
+                                         int pic_width,
+                                         int pic_height,
+                                         YUVType yuv_type)
+{
+#  if defined(MOZILLA_MAY_SUPPORT_NEON)
+  return (yuv_type != YV24 && supports_neon());
+#  else
+  return false;
+#  endif
+}
+
+} // namespace gfx
+
+} // namespace mozilla
+
+#endif // HAVE_YCBCR_TO_RGB565