[MEncoder-users] encoding for chroma key

[Rich Felker]

On Sun, Nov 27, 2005 at 11:26:20PM +0100, Aleksandar Uzelac wrote:
> 
> > >   now, am i missing something? is this the right way to go?
> > 
> > yes, you're missing the fact that video is 4:2:0 subsampled. it is not
> > made for doing this kind of thing.
> 
>   it's been five years since i worked on mpeg4 implementation, remind me what is 4:2:0 subsampling is?

chroma planes are only sampled at half the spatial resolution. i.e.
luma is 720x480 while choma is 360x240.

>   and lil' help as for what can solve this problem?

either don't use mpeg-type codecs, or do your color keying in yuv
4:2:0 rather than in rgb space.

rich