Consistently use get_prob(), clip_prob() and newly added clip_pixel().

Add a function clip_pixel() to clip a pixel value to the [0,255] range
of allowed values, and use this where-ever appropriate (e.g. prediction,
reconstruction). Likewise, consistently use the recently added function
clip_prob(), which calculates a binary probability in the [1,255] range.
If possible, try to use get_prob() or its sister get_binary_prob() to
calculate binary probabilities, for consistency.

Since in some places, this means that binary probability calculations
are changed (we use {255,256}*count0/(total) in a range of places,
and all of these are now changed to use 256*count0+(total>>1)/total),
this changes the encoding result, so this patch warrants some extensive
testing.

Change-Id: Ibeeff8d886496839b8e0c0ace9ccc552351f7628

1 files changed, 3 insertions, 16 deletions

diff --git a/vp9/decoder/vp9_dequantize.c b/vp9/decoder/vp9_dequantize.c
index 22a66716f..9e382914b 100644
--- a/vp9/decoder/vp9_dequantize.c
+++ b/vp9/decoder/vp9_dequantize.c
@@ -13,6 +13,7 @@
 #include "vp9/decoder/vp9_dequantize.h"
 #include "vpx_mem/vpx_mem.h"
 #include "vp9/decoder/vp9_onyxd_int.h"
+#include "vp9/common/vp9_common.h"
 
 static void add_residual(const int16_t *diff, const uint8_t *pred, int pitch,
                          uint8_t *dest, int stride, int width, int height) {
@@ -20,14 +21,7 @@ static void add_residual(const int16_t *diff, const uint8_t *pred, int pitch,
 
   for (r = 0; r < height; r++) {
     for (c = 0; c < width; c++) {
-      int a = diff[c] + pred[c];
-
-      if (a < 0)
-        a = 0;
-      else if (a > 255)
-        a = 255;
-
-      dest[c] = (uint8_t) a;
+      dest[c] = clip_pixel(diff[c] + pred[c]);
     }
 
     dest += stride;
@@ -43,14 +37,7 @@ static void add_constant_residual(const int16_t diff, const uint8_t *pred,
 
   for (r = 0; r < height; r++) {
     for (c = 0; c < width; c++) {
-      int a = diff + pred[c];
-
-      if (a < 0)
-        a = 0;
-      else if (a > 255)
-        a = 255;
-
-      dest[c] = (uint8_t) a;
+      dest[c] = clip_pixel(diff + pred[c]);
     }
 
     dest += stride;