[mythtv-users] Re: MythTV caoture cards

[Ray Olszewski]

Timothy -- Because this question is likely to be of interest to other 
MythTV users as well as you, I took the liberty of Cc'ing the myth-users 
list with this reply.

At 12:53 PM 9/9/2003 -0400, Timothy Wagner wrote:
>Ray,
>
>Thanks ever so much for your creation of the "video capture card list for 
>MythTV" two months ago. Has this FAQ been updated, and is it posted to any 
>web site?

Not by me. Unless Robert added it to the Myth HowTo, or Isaac put it on the 
Myth site somewhere, the version you found (in one of my e-mails to the 
list, perhaps?) is probably the only version that exists. Since I wrote it, 
I stopped using MythTV myself, so I haven't had any incentive to keep it up 
to date. (I stay on the Myth list because it remains the best place I've 
found to keep up on PVR issues generally, but I'm no longer very active on it.)

>Can you offer any advice on card selection? Here is my criteria:
>
>1. support for two identical cards.
>2. capture resolution at least 480x480
>3. stereo audio
>4. btaudio or similar audio capture driver
>
>I realize that the PVR-250 meets this spec but I would like to find 
>something cheaper, and without the MPEG2 encoder so that I can use VBI, 
>and record directly to RTJPEG or MPEG4.

Any card that works as a single card should work in this configuration, 
with two qualifications:

1. Not all cards support btaudio, and figuring out which ones do is a bit 
tricky. The Myth list has a lot of discussion of btaudio, and I think I 
tried to pull it all thgether once. You might see if I posted a message 
with a draft btaudio discussion, or if anything has been incorporated into 
the Myth HowTo.

2. If you use two cards that encode in software (e.g., bt878 cards), you 
will need a fast CPU to handle simultaneous encodes. The rule of thumb that 
I and others used was that an MPEG4 encoding stream , at resolutions 
similar to your target, requires 1 GHz of CPU (I don't know the equivalent 
for RTJPEG). Remember though, this is only a rule of thumb, NOT an exact 
calculation.

The second qualification *may* cancel out the cheapness of (say) bt878 
cards relative to PVR-250s. Or it might make a mixed strategy ... one bt878 
cars, one PVR-250 ... a better choice. Hard to say (impossible to say in 
the abstract, I suspect).

>In lieu of audio capture I'd need info on making two capture cards work 
>with one audio card. I didn't think this could be done.

That is my understanding as well.

>Thanks for any advice you can give.
>
>Timothy Wagner