[mythtv-users] what cards and tools

match at ece.utah.edu match at ece.utah.edu
Tue Nov 30 20:53:33 UTC 2004


On 30 Nov 2004 at 8:31, Cook, Garry wrote:

> although the answer to #1 has me confused again.

Maybe I can add to your confusion   ;-)
> 
> >From what Wayne says, the PVR250 may be better for me, because while I
> don't have HDTV capabilities right now, I will most likely want them in
> the future, and the 350 sounds like it's no good for this.

The 350 is a good choice for displaying a standard NTSC source on a standard NTSC 
TV set. 

What is your display? I run a projector that the PVR-350 can't drive anyway, so for me 
it's a no-brainer, I use a PVR250.

Both are useless for HDTV. Go here: http://www.pchdtv.com/ to see what's required for 
HDTV on MythTV.

> Although
> previously I was leaning towards the 350's, thinking that the decoder
> would be useful for keeping CPU low during playback (probably going to
> run this on an old PIII 800).

The 350 will help this, but if you are thinking of adding HDTV capability later, a PIII-800 
is not enough (someone on the list is going to disagree, but why endure the pain. 
Besides, the current pcHDTV card probably won't run on your motherboard, even if it 
was fast enough.) So,  if you'll be upgrading this box later to faster hardware to do 
HDTV,  at that point you won't need the decoding half of the 350 because you'll have 
CPU clock cycles to spare, or maybe you'll use a display card that includes some 
MPEG decoding in it, so why bother? 

If you are going to leave this machine as it is for watching/recording standard TV, then 
buy a PVR350.

I would go with the PVR250. With it, your PIII-800 will be able to record a program while 
watching it or while watching something that you recorded earlier... but not much else, 
and then move it to the new faster HDTV box that you are going to build for capturing 
standard TV on it.
> 
> What are the trade-offs of using a PVR-250 instead of a PVR350?

Kinda been answering this. Here's more:

Think of the 350 as 2 cards in one. It contains a 250, which is the part that captures the 
signal, converts it to MPEG and squirts it onto the computer bus so that the computer 
can display it, or record it, or whatever you want to do with it. The 350 also contains 
hardware that accepts MPEG data from the computer, decodes it into standard video 
and squirts it to your TV set or similar display.

So, you have 2 choices for standard video. Use a PVR350 and let it do the encoding of 
video to MPEG as well as decoding the MPEG back to video for the TV set, or use a 
PVR250 to capture the signal and encode it to MPEG for the computer, and let the 
computer decode the MPEG and send it through your VGA display card for display on 
any display device you want.

> Since I want to be able to record a show while watching TV, I need two
> cards (right?), 

Each card (PVR250 or the capture half of a PVR350) can capture one signal at a time. 
So if you want to record one channel while watching a different channel live, that takes 
2 cards. If you want to record one channel while watching something that you previously 
recorded or watch what's currently recording, that takes 1 card. If you want to record 3 
channels at once, that take 3 cards.

> Has anyone put together a Pros and Cons document related to tuner cards?
> Any recommendations on previous threads or search terms to look for in
> the archives?

In a nutshell, there are 3 kinds of cards: those in the $30-$50 range that just capture the 
signal and let the computer convert it to MPEG for recording, those like the PVR250 or 
M179 that also do the MPEG encoding in hardware, for about $100 more, or the 
PVR350 that is really a PVR250 that also decodes the MPEG file for display on a TV for 
about another $50. 

Getting a card with the hardware encoder will be the best extra $100 you can spend, I'm 
not so sure about including the hardware decoder for yet another $50...

Search http://ivtv.sourceforge.net/ for more info about PVR250-type cards, and Jarod 
lists some example hardware configurations on his site: http://wilsonet.com/mythtv/

Marvin



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