Alright, I have a MythTV box right now running on a 1.1 Ghz celeron, 384MB RAM, and through a PVR-350 s-video out.

I'm looking at a choice of two machines right now to replace this box with. I'd like to be able to do HD but I don't know if either of them will be able to handle it.

PC #1: Pentium 4 2.4GHz running on a 400mhz FSB with a socket 478/423 adapter. The machine has 384MB PC800 RDRAM and an AGP Radeon 9800 Pro.

PC #2: Pentium 4 2.53Ghz running on a 533mhz FSB. 512MB PC3200 with integrated graphics. I could add an nvidia fx6200 pci card if necessary.

What do you think? Could they do HD?

They might. IF you had nvidia with XVMC they certainly could. I have a P4 2.6 (hyperthreading) that does HD without XvMC without any problem (geforce 440MX - 2GB pc3200, although I had HD running fine with 1GB - never tried it with less).

use #2 and get an nvidia card that supports xvmc. I got my fx5200 for like $25 from newegg a few years ago.

I'm just hesitant to go out and spend money on an HD tuner when there's no guarantee the machine is powerful enough to decode the higher resolution content.

I have a PCI FX5200 (not 6200 as originally posted) that I can put in the machine. The machine does not have an AGP port but that shouldn't be a problem, right?

Also, I have the backend set to transcode everything to mpeg4 after flagging the commercials. I imagine I'll have to keep everything in mpeg2 or the machine might not be able to play it. Am I correct in thinking this?

Finally, do Axel's RPM packages for Fedora include xvmc support or do I have to compile mythtv on my own?

I'm just hesitant to go out and spend money on an HD tuner when there's no guarantee the machine is powerful enough to decode the higher resolution content.
You could look into a hardware encoding HDTV card. I can't recommend any ('cause I don't know). I did hear that Hauppauge has one, or is planning on one.

Also, I have the backend set to transcode everything to mpeg4 after flagging the commercials. I imagine I'll have to keep everything in mpeg2 or the machine might not be able to play it. Am I correct in thinking this?
If you transcode everthing to mpeg4, just about any machine should be able to play it. I tried to use my laptop for a frontend. With its Intel onboard graphics, I was not able to watch live HDTV, only the digital stations broadcasting in SD. However, I could watch the HDTV shows that I transcoded to MPEG4

Finally, do Axel's RPM packages for Fedora include xvmc support or do I have to compile mythtv on my own?
I was never able to get Axel's nVidia drivers to work on my system. I always had to download the drivers from nVidia

I currently am running MythTV on SuSE 10.1 with the driver from the nvidia website. I just realized that XvMC is faulting, and not being used. I updated drivers, with the same result. Not sure if that relates to the question.

The way I discovered the problem with XvMC, was to run the frontend in verbose mode. To do that, open a terminal shell and run the frontend from there.
mythfrontend -v important

or

mythfrontend -v help (to list more options)

Paul

P. S. I see your question was about Axel's MythTV RPMs, not his nVidia RPMs. my mistake.

I'm just hesitant to go out and spend money on an HD tuner when there's no guarantee the machine is powerful enough to decode the higher resolution content.

I have a PCI FX5200 (not 6200 as originally posted) that I can put in the machine. The machine does not have an AGP port but that shouldn't be a problem, right?

Also, I have the backend set to transcode everything to mpeg4 after flagging the commercials. I imagine I'll have to keep everything in mpeg2 or the machine might not be able to play it. Am I correct in thinking this?

Finally, do Axel's RPM packages for Fedora include xvmc support or do I have to compile mythtv on my own?

Is it a PCI FX5200 or a PCIe 5200? I don't think PCI has the bandwidth to decode HD signals. You'll probably need it to be AGP or PCIe.

You could just download or get some HD mpeg2 files and try playing them before you buy the tuner to see. You can try with and without XvMC. You can also do this with your mp4s.

Another issue is what codec?

HD files floating around are encoded as mpeg2, Xvid, Divx, WMV9, VC1 and H264, in order from least CPU intensive to most intensive (Xvid/Divx probably equal).

H264 HD might not play on your proposed rigs.

Also, 720p vs 1080i/p makes a difference. You might be able to play H264 720p HD files, but not 1080p, for example.