Mythtv HD requirements

dakor · 2007-05-08 23:14:13

Hey I am planning on building a Mythtv box for the living room. I am kind of tight on money and want to do this without breaking the bank. What I my main question is how fast of a Cpu and Ram would I need to watch and record HD channels. The box will be running both the frontend and backend. I also plan on buying a hardware based TV card so that should take most of the load.

I read here that I need at least an Athlon64 3200+ to play back HD without lag but I really want to know if I have to spend that kind of money haha.

Echo · 2007-05-09 02:55:41

AFAIK, MythTV has some problems with xvmc support, which is a must have if you're going to try to use an underpowered box. I have an AMD Athlon 1800 chip playing back hdtv recorded shows "with mplayer" and xvmc enabled. I have to use -framedrop and -nocache to get it to play back without incident. So, I think, this is about as low as you could go and is cutting it pretty close, ymmv. Supposedly, xvmc support is to improve when myth .21 is released. I think I'll check out mythtv's ability for playback once .21 is available. Note that I use the Athlon 1800 box only as a frontend. I record my hd shows on another box. I know this isn't exactly what you were looking for (frontend only for me) so take it for what it's worth. Hopefully, someone else will speak more directly to your question.

dakor · 2007-05-09 03:14:17

Well what kind of machine would I need to play HD without using xvmc ?

ould · 2007-05-29 21:35:19

dakor wrote:

Well what kind of machine would I need to play HD without using xvmc ?

Just for reference I am currently running a combined Frontend/Backend machine with the following specs:

AMD64 3700+(single processor not X2)
1 gig ram
A couple SATA drives for recording and storage
Regular IDE drive for OS and other assorted files
GeForce 512mb 6600(fanless :0)
Avermedia A180 ATSC (for OTA HD)
Twinhan DVB-S card for Satellite(Both SD and HD)

I can "playback" and record pretty much anything smoothly running my system at 1080i(I wish my tv did 720p as I would opt for that). However, there are a few channels which for some reason I can't watch in LiveTV mode smoothly, they are very jerky, I have not narrowed down the issue as of yet and am unsure if those same channels also record jittery as they are on channels I don't record from or use too often. I have tried the system with and without xvmc and it doesn't seem to make much difference for these channels in question for my setup except I lose the coloured OSD with xvmc turned on. The channels I have trouble with are on the satellite feed, so it could just come down to a crappy signal(although I don't think that's the case) or something along those lines. I do 90% of my regular TV recording from the OTA card which seems to work well. I mainly use the satellite stuff for movies and channels I can't get OTA.

My setup is running ubuntu as I had a setup guide to follow and since it was my first MythTV setup it made it much easier. My main rig at home is Arch based at the moment and I may put a frontend setup on it at some point.

I keep debating whether it is worthwhile upgrading my graphics card to something better but unsure if it will make too much difference.

Hope that helps,

Kevin

QuimaxW · 2007-05-29 21:54:00

Having tried multiple MythTV setups...

1) Recording HD is a job a Pentium 3 733MHz can accomplish. (This was my HD backend for quite a while.) Since HD is simply an MPEG2 stream, all the system does is copy the stream to a file on the hard drive.

2) Playback is the difficult part. My frontend is a Pentium M 1.73 with onboard Intel 915 graphics. It took 3 weeks to get it tweaked properly to actually playback HD (especially 1080i) tv. It's the playback that requires all of the horsepower.

My backend is an Athlon XP 3000+ with 1GB of RAM, with the pchdtv hdtv card (www.pchdtv.com), and an NVidia 5200 series video card. It's an older card, however, once I had the proprietary driver loaded (see the arch wiki), HD playback was a breeze. I actually don't remember having to set anything to get it to work in MythTV. Using this system, I can record from one tuner, while watching livetv with the 2nd tuner. No frame drops so long as the signal is good.

All that said...two things I wouldn't skimp on would be hard drive and video card. 500GB hard drives are currently $130, you'll eat it up with HD recording. A good video card can enable almost any system to smoothly play HD content. If you'd like, I can post my full specs for my setup, but it can take a bit to compose...

Echo · 2007-05-30 16:26:04

ould wrote:

However, there are a few channels which for some reason I can't watch in LiveTV mode smoothly, they are very jerky, I have not narrowed down the issue as of yet and am unsure if those same channels also record jittery as they are on channels I don't record from or use too often.

I wonder if there is a file size difference (larger) in the channels you're having problems with. I know I have hour long shows that are 6+GB and some that are 4+GB.

You may also want to wait for the next version of myth to come out as I believe it's to have better xvmc support.

ould · 2007-05-31 13:03:14

Echo wrote:

I wonder if there is a file size difference (larger) in the channels you're having problems with. I know I have hour long shows that are 6+GB and some that are 4+GB.
You may also want to wait for the next version of myth to come out as I believe it's to have better xvmc support.

You may be right, it could be larger chunks of data and the system chokes when watching LiveTV. I am gonna try and record off one of these channels and see if playback is ok. Also I know alot of HD channels broadcast at 720p rather than 1080i so maybe the channels I am having trouble with are the ones broadcasting at 1080i, unfortunately it's not very clear which are broadcasting at either resolution. I guess I could tell off the recordings and see what the frame size is. As I mentioned I don't watch LiveTV too often(why watch commercials) and I have duplicates of the major broadcasters(fox, cbs etc) so I could just switch over to OTA instead. But also as usual I can't leave well enough alone have the time and want to have it working perfect.

While on the topic, is it at all possible to harness the power of SLI for our MythTV playback purposes? I haven't read of anybody doing it or even know if it's possible with either MythTV or Linux for that matter but thought it might be an interesting setup. Slam in like 2 7600GT's or 7900GT's or something like that. :-)

Kevin

QuimaxW · 2007-05-31 13:32:41

Try going through the playback settings and try a few different type of playback. My machines both like different settings. I believe one is set for Standard and the other is set for xv or something.

So far as SLI for playback, I havn't heard of it. I suppose it's possible though...

Arch Linux

#1 2007-05-08 23:14:13

Mythtv HD requirements

#2 2007-05-09 02:55:41

Re: Mythtv HD requirements

#3 2007-05-09 03:14:17

Re: Mythtv HD requirements

#4 2007-05-29 21:35:19

Re: Mythtv HD requirements

#5 2007-05-29 21:54:00

Re: Mythtv HD requirements

#6 2007-05-30 16:26:04

Re: Mythtv HD requirements

#7 2007-05-31 13:03:14

Re: Mythtv HD requirements

#8 2007-05-31 13:32:41

Re: Mythtv HD requirements

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