static int h263p_decode_umotion(MpegEncContext * s, int pred)
{
   int code = 0, sign;

   if (get_bits1(&s->gb)) /* Motion difference = 0 */
      return pred;

   code = 2 + get_bits1(&s->gb);

   while (get_bits1(&s->gb))
   {
      code <<= 1;
      code += get_bits1(&s->gb);
   }
   sign = code & 1;
   code >>= 1;

   code = (sign) ? (pred - code) : (pred + code);
   ff_dlog(s->avctx,"H.263+ UMV Motion = %d\n", code);
   return code;

}

This weakness involves numeric computation errors, such as integer overflows, underflows, or precision losses, which can lead to miscalculations and exploitable behaviors in software.