[mythtv-users] HD on SDTV playback question

[Steven Adeff]

On 2/26/07, jason maxwell <decepticon at gmail.com> wrote:
> On 2/26/07, Steven Adeff <adeffs.mythtv at gmail.com> wrote:
> > On 2/25/07, Gary Raposo <gary at raposo.ca> wrote:
> > > At 03:26 PM 25/02/2007, you wrote:
> > > >On Sunday 25 February 2007 12:26, Steven Adeff wrote:
> > > > > On 2/25/07, Paul Bender <pebender at san.rr.com> wrote:
> > > > > >
> > > > > > Most of the frontend's power is used to decode the video. Therefore, the
> > > > > > power needed depends on the resolution of the content much more than the
> > > > > > resolution of the display. Of course, by today's standards, a below
> > > > > > average computer system can decode and display HDTV.
> > > > >
> > > > > If the other frontends have an FX5200 or better you can use XvMC to do
> > > > > the decoding if the CPU isn't fast enough.
> > > >
> > > >Up to a point, yes, but XvMC isn't a magic bullet. On my system (an Intel
> > > >Celeron D 3.06GHz), using XvMC with an nVidia MX4000 and nVidia's drivers
> > > >produces smooth playback with CPU loads of around 50-60% for mythfrontend
> > > >when playing back HD content on an SD screen (800x600 resolution), with X
> > > >chewing up another 5-10%. Disabling XvMC but using the same card kicks CPU
> > > >use up to around 80%, IIRC, with playback remaining smooth -- but it gets
> > > >unsmooth quickly whenever you do anything (skip back, etc.). Swapping in a
> > > >video card based on a SiS Xabre chipset, which can't do XvMC, produces choppy
> > > >playback with higher CPU loads for both mythfrontend and X (around 80% for
> > > >mythfrontend and 20% for X, IIRC). Cutting playback speed down to 60-90% of
> > > >normal typically produces smoother playback. Based on this, I'd guesstimate
> > > >that XvMC reduces HD playback CPU load by 25-50%. This is good, of course,
> > > >but it's nowhere near as much of a reduction as you see when using hardware
> > > >encoding cards vs. simple frame grabbers.
> > > >
> > > >That said, results are likely to vary from one card to another. My
> > > >understanding is that the cards with the most hardware acceleration delivered
> > > >by XvMC are those based on the nVidia 5200FX series.
> > > >
> > >
> > > Sorry to butt into your discussion but you've touched on something
> > > that I've been wondering about for some time now.  I've got an
> > > original Asus Pundit (2.4GHz P4 with onboard SiS chipset driving its
> > > S-Video TV-out) configured as a SD frontend.  My backend is capturing
> > > HD (it's also my primary frontend driving an HD display).  I haven't
> > > had any success with smooth playback of HD content scaled down to SD
> > > on the Pundit and I assumed that the processor was simply not up to the task.
> > >
> > > Are you saying that if I go out and get myself a 5200FX based video
> > > card and turn on XvMC then I'm in business?  Remember that this video
> > > card would have to be a PCI based card... not AGP or that newfangled
> > > PCI-E.  Do you think this configuration could do it?
> >
> > Gary,
> >
> > I believe it was determined that with XvMC enabled the PCI bus is
> > capable of handling 1080i display. It would probably behoove you to
> > search the list archives first to be sure, but I believe that was the
> > conclusion that was made. The other option, if possible, is to upgrade
> > the processor on the Pundit to something that can handle 1080i
> > decoding.
>
> So are you guys saying that the 5200 based cards will do a better job
> rendering HD content than it's successors? or is it 5200 or newer that
> I should be looking for?
> I ask because finding either a PCI-e 5200 card, or an AGP slot on a
> modern mobo, will severely limit the possible configurations of my
> planned system.

5200 or newer is what is recommended. So for PCIe go with a 6200TC,
its cheap, fan-less and works quite well (many of us HD users run this
card).

-- 
Steve
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