On Tue, 01 Dec 2009 08:53:01 PST
Dieter <[email protected]> wrote:
> > DGA was used in the days before Xvideo to have a fast path
> > to the graphics card. It was done by giving the X client
> > a portion of the graphics card memory as dumb framebuffer.
> > AFAIK the only use was for software renderer and vido players.
> > It's main disadvantage was that it could not operate in a
> > window and thus had to switch into fullscreen. After the release
> > of XF86 4.0 its already little usage was reduced to zero.
> >
> > IIRC only MPlayer and VLC still support DGA output.
>
> Sounds like this DGA thingy breaks the X11 model and would
> only work if the client and server are on the same host?
There are a few systems that break the network transparent model
of X11. DGA is one of them, XVideo another. IIRC early implementations
of DRI/DRM needed the client to be on the same host as the server too
(dunno how it is today).
> Speaking of video decoding, that's the one thing ATI hasn't
> documented, and might not ever document due to fear of
> flying chairs. Which leaves a market opportunity for OGP.
> Given the existance of low wattage video decoding chips
> I assume that video decoding doesn't need nearly as many
> gates as 3D graphics, which seems to need a direct feed from
> your local hydroelectric plant. Fewer gates implies
> lower fab costs and perhaps faster design time.
Video decoding is unfortunately a little bit more involved than
3D graphics. While with 3d you only have to deal with well formed
request and can any bad request on the application writer, you have
to deal with broken data with video decoding in a way that does not
fall apart with the first flipped bit. Not to mention that the only
good documentation of video coding available are the standard documents
of MPEG and ITU... everything else either stops at the very basics or
discusses some esoteric topics that noone cares about.
Having said that, video decoding for OGP has been on my todo list
for ages, but given the time i was able to devote to OGP in the past,
i don't think i'll be able to provide anything substantial until OGA2. :-(
On the other hand, if someone is willing to work on this, i'll be glad to
bring you together with people who could help you with learning about
video coding and how to correctly design a decoder.
Attila Kinali
--
If you want to walk fast, walk alone.
If you want to walk far, walk together.
-- African proverb
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