[mythtv-users] Which NVidia card

Steve Smith st3v3.sm1th at gmail.com
Mon Jan 21 14:34:15 UTC 2008

On 21/01/2008, Cal <cal at graggrag.com> wrote:
> Marius Schrecker wrote:
> > Hi,
> >
> >    After a Loooong break I'm trying to breathe new life into my MythTV
> box.
> >
> > Why didn't I listen to you all before when you warned bout ATI cards?
> I'd
> > have saved myself a lot of grief! Anyway:
> >
> > Now I'm going to get a card that does proper XvMc (Nvidia the only
> choice
> > here??)
> >
> > The box will only be used for MythTV, so great 3d performance is not an
> > issue.
> >
> > Card should be PCIe, available (7000 series or 6200TC), passive, and not
> > generate too much heat. I'va lso read mixed reports on whether the 7000
> > series DOES support full XvMc, so questions are:
> >
> > 1. Is it correct that the 7000 series does XvMc without problems?
> > 2. I can still get hold of a 6200TC, but this has only 64 MB Ram. Is
> this
> > sufficient?
> > 3. Will the 7300 GS produce much more heat than a 6200TC? Could I
> > underclock to compensate?
> >
> >
> > 4. Other recommendations????
> Forget about XvMC. It's a relic of a past era where our poor struggling
> sub-2G single core cpus _needed_ some graphics processing to be offloaded
> in
> order to survive. So, the poor little graphics card endured constantly
> cooking up a storm doing XvMC, and without even a fan to cool its brow.
> Now, I believe you're better off letting a nice little dual core do the
> hard work. It's better equipped to deal with the heat output too.
> Worst of all, XvMC comes with some tedious artifacts. You don't get
> anything
> for free. My suggestion is have the graphics card do no more than it has
> to,
> and provide the necessary grunt via cpu instead. I have a 6200 and a 7300
> (two systems), and I really can't pick between them. They're both
> excellent as
> long as I don't try to include XvMC in the mix.
> Cheers.
> (I could really use a "Loooong break", can you recommend a good source?)
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That's an interesting take on the use of XvMC.
My opinion is use a specialized tool for a specialized job.
 The XvMC circuitry on a video card is specifically designed to assist in
some of the heavy and specific tasks required in decoding mpeg2, as such it
is likely to do this much more efficiently than a general purpose CPU is.
If you take this idea to an extreme you get a full hardware decoder such as
that on the PVR-350, which only uses a very small heatsink (read low power
consumption) compared with the large heatsink (and fan) required for your
average CPU. (All other issues with the PVR-350 aside)

That said XvMC does introduce some complications (as you point out):
     1) Driver support can be "fussy".
     2) The black and white OSD problem.
     3) It only works for MPEG2 at the moment. So if you want to play
anything other than MPEG2 then it's useless. This is particularly relevant
if you're looking at HD support.

So basically if you're only decoding MPEG2 (or just SD) then XvMC is still
likely to be usefull, taking some load off your CPU for other tasks. ( I
currently run on a PIII 900Mhz so I like to offload whenever I can).

Just my opinion mind...


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