[FFmpeg-devel] [RFC] use ff_avc_find_startcode in ff_find_start_code

[Reimar Döffinger]

Hello,
On Tue, Feb 19, 2008 at 06:22:30PM +0100, Michael Niedermayer wrote:
> if(p[1]){
>     if( p[2] == 0 && p[4] == 1 )
>         return p+1;
>     if( p[4] == 0 && p[5] == 1 )
>         return p+2;
> }else{
>     if( p[0] == 0 && p[2] == 1 )
>         return p-1;
>     if( p[2] == 0 && p[3] == 1 )
>         return p;
> }

I think that does not work for
00 00 00 00 01

> Should be faster IMO, also the original code in the if() should be faster
> than your code. Only the change in the masks for BE/LE looks like it should
> improve speed.

However it looks, at least my current variant is faster (for all I can
test, and the difference is minimal, possibly even in the measurement
error range):
            if ((x & 0x0000ffff) == 0x00000100 && p[-1] == 0)
                return p-1;
            if ((x & 0x00ffffff) == 0x00010000)
                return p;
            if ((x & 0xffffff00) == 0x01000000)
                return p+1;
            if ((x & 0xffff0000) == 0 && p[4] == 1)
                return p+2;

Greetings,
Reimar D?ffinger