svq1dec: simpify mean calculation.

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/svq1dec.c

@@ -202,7 +202,7 @@ static const uint8_t string_table[256] = {
         entries[j] = (((bit_cache >> (4*(stages - j - 1))) & 0xF) + 16*j) << (level + 1);\
       }\
       mean -= (stages * 128);\
-      n4    = ((mean + (mean >> 31)) << 16) | (mean & 0xFFFF);
+      n4    = (mean << 16) + mean;
 
 static int svq1_decode_block_intra (GetBitContext *bitbuf, uint8_t *pixels, int pitch ) {
   uint32_t    bit_cache;