[mythtv-users] Accuracy of HDTV processor requirements statement in HOWTO

Jerry Rubinow jerrymr at gmail.com
Tue Feb 7 19:53:34 UTC 2006


On 2/7/06, Robert Kulagowski <bob at smalltime.com> wrote:
>  From the HOWTO:
>
> "
> To playback HDTV content, plan on a powerful CPU.  "How powerful?"
> depends on a number of factors, such as the capture resolution, whether
> the video is progressive or interlaced, and whether your display card
> has hardware-assist support for Linux. For 720p content (1280x720), a
> 2.4GHz P4 should be sufficient.
>
> For 1920x1080i->1920x1080p with the better deinterlacing methods
> done in real time a 2.4GHz CPU is taxed, but should work if you use "Bob
> and Weave" deinterlacing, or if you have an NVIDIA card with MPEG-2
> hardware acceleration.  If you enable the hardware acceleration, you may
> be able to use a 1.8GHz processor.
> "
>
> I'm looking for feedback from people that are running HDTV with
> lower-end processors; I've got a 2.4Ghz HT P4, nvidia 7676 and a 1080i
> program with XvMC still surges:  about 2 seconds of regular speed, then
> a micropause of about .5 seconds, then repeat; not sure if this is tied
> into trac bug #1219 or if it's CPU bound.  I'm even more concerned with
> the statement that a 1.8Ghz should be good enough.

I fooled around for months trying to get HD playback working on a
(original) Pundit with 2.8GHz non-HT P4, conncted to a 720p tv.  I
tried both with the onboard Sis graphics and with an FX5200 PCI card. 
But I never could get something satisfactory.

Through the 5200, playback was always too slow/stuttery without XvMC -
probably maxing out the PCI bus.  With XvMC, I had very low CPU usage
but either it would be crashy or lock up occasionally or also be
stuttery.  I could play the same file with mplayer w/ XvMC without a
problem.

Through the Sis, it seemed to max out the CPU.

I've seen other people claim they were able to get HD going fine on
the Pundit, so I don't know what the problem could be.  I can only
assume when you set up a system for HD, either it just works, or you
have no end of problems.

I'm currently (until I get new frontend hardware) running a combined
FE/BE on an ASUS a7n8x-x with an AGP FX5200, and I can play the 720p
ok not using XvMC.  Haven't done extensive tests to see how much I can
load the system down with recording and still have it play back
acceptably.  However, when trying to use XvMC, it's crashy/stuttery.

And yes, I'm using a 7676 version driver.

Sorry I can't tell you something more definitive.  If you want some
more details about what I've tried I can give you pointers to some of
my old posts.

But as for info that would be useful to other people - a PCI bus
doesn't seem to have enough bandwidth for 720p.  If you're going to do
HD you should compile with enable-proc-opts.  It can be tricky to find
the right mix of setup options to make HD work well.  Even on the
much-recommended FX 5200, it can be impossible to get XvMC working
(I'm not discounting the possibility that there's something glaringly
obvious I overlooked, but I spent a lot of time trying).  Use extra
audio buffering and opengl vsync, unless they slow things down, in
which case don't use them.

-Jerry


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