[XviD-devel]

[=?gb2312?B?w8+/wg==?=]

Hi,
   I'm reading the source code of xvidcore-0.9.1. There is something in src\motion\sad.c making me a little puzzled.Can anyone help me?
   The part annoying me is listed here:
uint32_t
sad16bi_c(const uint8_t * const cur,
    const uint8_t * const ref1,
    const uint8_t * const ref2,
    const uint32_t stride)
{

 uint32_t sad = 0;
 uint32_t i, j;
 uint8_t const *ptr_cur = cur;
 uint8_t const *ptr_ref1 = ref1;
 uint8_t const *ptr_ref2 = ref2;

 for (j = 0; j < 16; j++) {

  for (i = 0; i < 16; i++) {
   int pixel = (ptr_ref1[i] + ptr_ref2[i] + 1) / 2;

   if (pixel < 0) {
    pixel = 0;
   } else if (pixel > 255) {
    pixel = 255;
   }
    Since ptr_ref1[i] and ptr_ref2[i] are two unsigned byte,why   is it possible that pixel < 0 or pixel > 255 ?Thanks very much





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