On Thu, Nov 25, 1999 at 09:41:06PM +0100, Andreas Beck wrote: > Hi ! > > > i thought about the yuyv-topic again. a packed yuv422 buffer can be > > transformed into a planar yuv422 buffer. this way you get 3 buffers. one for > > Y (size is T), one for U (size T/2) and one for V (T/2). can't this buffer > > be accessed like those vga 4-bit plane-buffers ?? > > No. VGA-4-plane was handled in a somehat weird way, right. We used a planar > read configuration and a color-switched write configuration. > > However the assumption, that each single pixel can be controlled individually > still held. > > The YUVU setup is different. It basically doesn't really fit the GGI > picture of a "normal" graphics mode. > > For the operations covered by LibGGI I would suggest to handle it like a > mode that has the "Y" resolution. Thus if you set a pixel, the neighbouring > pixel will get the same color values u/v as well. This is IMHO the only > consistent way out. It isn't too bad, as the reason for subsampling u/v is, > that the eye has not as much resolution for color than for greyscale. > > It has some strange implications for read/modify/write stuff, though. > Well - on colormapped modes we have similar problems. > > For the DirectBuffer we might want to define a new possible entry for the > bitmeaning field that would mean "u on even pixel numbers v on odd ones" > or similar. > > The other alternative would be to allow some new kind of directbuffer that > can hold multiple entries, one for each "plane" (the planes happen to be > stored in an interleaved fashion in our case). This would more generically > allow for such subsampled formats. i vote for this one. this is the only reasonable way that covers all my needs in handling the buffer, but i doesn't cover the packed layout i can get from the tv-card nor it does cover the layout your gfx-card is using. (YUV422 is nost often packed) i can live with the planar ones. > There is also a double-subsampled format, where a pixel-quad (2x2) shares u,v > but has 4 y values. My hardware doesn't have that - do you know, how it is > stored ? v4l2-page: http://millennium.diads.com/bdirks/v4l2fmt.htm there are 4:2:2 - packed - YUYV 4:1:1 - packed - YYYUYYYU YYYVYYYV 4:2:0 - planar ! - your mentioned 2x2 matrix (don't know it's layout in memory) 4:1:0 - planar ! > > i really this a ggi-support for this topic and need your opinions and > > suggestions to set something up that take care of colorspaces != RGB. > > Yes. I have an application for that as well. can you talk about it ?? some mpeg-stuff ? > Well, we have hardware devices that export those formats - TV-out cards. > So we somehow have to cover them. And I'd really like to be able to run > LibGGI apps on _anything_, so ... > > CU, ANdy > > -- > = Andreas Beck | Email : <[EMAIL PROTECTED]> = thats all Jan --- -)= Jan Kneschke -- Kiel -- Germany -- http://www.kneschke.de =(-
