[XviD-devel] 8bit greyscale

[Michael Militzer]

Hi,

Quoting Christoph Lampert <chl at math.uni-bonn.de>:

> On Tue, 15 Mar 2005, Michael Militzer wrote:
> 
> > Hi,
> > 
> > there's a greyscale encoding option in XVID already for a long time (and
> > such an option also exists in the VfW GUI). If the XVID_VOP_GREYSCALE flag
> > is set, chroma information is dropped in the encoder. That should be
> > sufficient I think - there's no need to set U and V to 128 in colorspace
> > conversion if the chroma information is later omitted anyway...
> 
> Yes, I know about the GREYSCALE flag (wasn't it me who added it? I 
> don't remember). But I didn't mean only encoding at greyscale (possibly 
> from color input), but about using only planar 8bit greyscale as input
> colorspace. It seems that there is no possiblity to feed that directly 
> into XviD without padding it with 128s, although it seems that some 
> cameras can produce it. 
> 
> Internally, one can of course use XVID_CSP_USER and set U and V point to 
> something constant, but it seems that the VfW-GUI doesn't accept 8bit 
> input in that way. 

Well, internally you could use XVID_CSP_USER, use the greyscale image as 
y-plane and don't care about U/V values at all. Iirc, if you set the 
XVID_VOP_GREYSCALE flag the chroma information is omitted anyway, so there's
no need to set the chroma planes to constant values.

So VfW support could be added without modifying xvidcore. I just wonder if
VfW supports 8-bit greyscale input at all. I only know of 8-bit indexed RGB
in VfW - but I'm no expert regarding the supported VfW colorspaces. So even
if a camera natively works in 8-bit greyscale mode, the VfW driver may
automatically convert the images to RGB...

Michael