simple_idct: idct_4col_put: Fix out of array reads.

Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/simple_idct.c

@@ -53,7 +53,6 @@
 static inline void idct4col_put(uint8_t *dest, int line_size, const DCTELEM *col)
 {
     int c0, c1, c2, c3, a0, a1, a2, a3;
-    const uint8_t *cm = ff_cropTbl + MAX_NEG_CROP;
 
     a0 = col[8*0];
     a1 = col[8*2];
@@ -63,13 +62,13 @@ static inline void idct4col_put(uint8_t *dest, int line_size, const DCTELEM *col
     c2 = ((a0 - a2) << (CN_SHIFT - 1)) + (1 << (C_SHIFT - 1));
     c1 = a1 * C1 + a3 * C2;
     c3 = a1 * C2 - a3 * C1;
-    dest[0] = cm[(c0 + c1) >> C_SHIFT];
+    dest[0] = av_clip_uint8((c0 + c1) >> C_SHIFT);
     dest += line_size;
-    dest[0] = cm[(c2 + c3) >> C_SHIFT];
+    dest[0] = av_clip_uint8((c2 + c3) >> C_SHIFT);
     dest += line_size;
-    dest[0] = cm[(c2 - c3) >> C_SHIFT];
+    dest[0] = av_clip_uint8((c2 - c3) >> C_SHIFT);
     dest += line_size;
-    dest[0] = cm[(c0 - c1) >> C_SHIFT];
+    dest[0] = av_clip_uint8((c0 - c1) >> C_SHIFT);
 }
 
 #define BF(k) \