[MPlayer-DOCS] en/mplayer.1: bugs and question

[Torinthiel]

On Fri, Oct 01, 2004 at 11:00:10AM +0200, Guillaume POIRIER wrote:
> > Is there meaning of DC a low resolution part of image? Allways is?
> > 5875: ...scplx_mask will reduce the quality of P blocks even if only DC 
> > is changing
> 
> I don't understand what you mean... but if your problem is to understand
> the meaning of DC, I can't help you with it right now, I don't know.

To tell what DC is you first need to know a little about JPEG ;)
JPEG is basically image transformed to YUV colorspace, divided into 8x8
blocks (sometimes U and V planes have larger blocks) and each block is
then subject to discrete cosine transform. Now the DC is the top-left
coefficient after that transform. So DC being a low-res picture is not
that far from the truth, but it also contains some information about
other pixels in this block. It's the single most important coefficient.
And in MPEG it's the same - I frames are more or less JPEG images.
Torinthiel

-- 
 Waclaw "Torinthiel" Schiller       GG#: 542916, 3073512
   torinthiel(at)megapolis(dot)pl
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