Moin,
On Wed, 28 Jun 2006 10:24:52 +0100
Dieter <[EMAIL PROTECTED]> wrote:
> > Of course, you can offload some parts of the decoding with
> > XVmc, but that functionality is not widely spread and doesn't
> > work for all codecs.
>
> This brings up the question of how much bandwidth do you need between
> the client and server if the client decodes? E.g. is Ethernet fast enough?
> If not, then we have to decode inside the X-video-server box.
for 720p, subsampled to 4:2:0, 30fps:
1280*720*2*30 = 53MByte/s
That's current state of the art, which means that the resolution
is still increasing.
If you really want to decode video on the x server box,
then you have to run the player there. There are so many
different codec types that it's hardly possible to use something
like Xvmc to decode them all. The only thing i can think of
is to transcode them on the client into a form that the X server
can understand, but that's either very cpu intensive or a big
los on quality.
But actualy, you do not want to have video and audio output
on different machines connected over a slow network. The
delay becomes unpredictable and thus A-V synchronisation
is very bad.
> > Modern schemes that
> > are wavelet based exceede this by a factor of 10 or even more.
>
> And I suppose we can expect a new incompatible-wrench-in-the-gears
> every couple of years for quite awhile. So we'll have to make a
> list of what the X-video-server will decode, and anything incompatible
> will have to be transcoded on a general purpose computer. Which is a
> major PITA.
Expect to do that already now. MPlayer currently supports something
in the range of 200 different video codecs. libavcodec (the main
decoding library) commes currently with over 50 codec schemes, most of
them decoding more than one video codec.
Even if you want to limit yourself to the most used codecs you'll
get way more than you can support (i'd say something in the range
of 20 codecs).
IMHO leave the video decoding to specialized apps. Just provide
them a facility to get their data onto the screen.
Attila Kinali
--
心をこめて聞け心をこめて話せ
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