Re: Video Coding Puzzle

Hi

On Friday 09 July 2004 20:01, Michael Niedermayer wrote:
> Hi
>
> On Friday 09 July 2004 17:17, Mike Melanson wrote:
> [...]
>
> > 0x3fa73d75 -> 1.306563
> > 0x3f0a8bd4 -> 0.541196
> > 0x3ec3cf15 -> 0.382439
> > 0x59c00000 -> 6755399441055744.000000
> >
> > however i had trouble defining these numbers as a float, since
> >
> > 1.306563 -> 0x3fa73d75
> > 0.541196 -> 0x3f0a8bd2                <---------------
> > 0.382439 -> 0x3ec3cf0b                 <---------------
> > 6755399441055744.000000 -> 0x59c00000
> >
> > which give a wrong result. This made me define those constants as
> > hexadecimal values instead of floating point numbers just to be on the
> > safe side (although this could be a quirk from Visual C++, i have yet to
> > verify this)
>
> u need to use more digits to uniquely store floats, try
> 		1.3065630,
cos(pi*2/16)sqrt(2)

> 		0.5411961,
cos(pi*6/16)sqrt(2)

> 		0.3824393,
ROTFL, this is wrong, its certainly supposed to be:
0.3826834  (0x3EC3EF15) = cos(pi*6/16)
compare:    0x3ec3cf15 

> 		6755399441055744.0000000
i suspect thats used for some fast float->int conversation

[...]
-- 
Michael
level[i]= get_vlc(); i+=get_vlc();		(violates patent EP0266049)
median(mv[y-1][x], mv[y][x-1], mv[y+1][x+1]);	(violates patent #5,905,535)
buf[i]= qp - buf[i-1];				(violates patent #?)
for more examples, see http://mplayerhq.hu/~michael/patent.html
stop it, see http://petition.eurolinux.org & http://petition.ffii.org/eubsa/en


-------------------------------------------------------
This SF.Net email sponsored by Black Hat Briefings & Training.
Attend Black Hat Briefings & Training, Las Vegas July 24-29 - 
digital self defense, top technical experts, no vendor pitches, 
unmatched networking opportunities. Visit www.blackhat.com