Hmmm, the code gruel has given was wrong. Here is the right one for obtaining a division by 2 when b is 1 and a division by 1 when b is 0: #define div_2(a, b) (((a)-(((a)>>31)&(-b)))>>(b)) This code is still 20s faster for the matrix trailer with my mplayer module, so if it's mathematicly correct... i think we should just commit. -- Edouard Gomez