[mythtv-users] 2 capture cards: want 1 dedicated to live TV, other to recording

Michael T. Dean mtdean at thirdcontact.com
Wed Dec 17 21:13:35 UTC 2008

On 12/17/2008 01:21 PM, James Miller wrote:
> Michael T. Dean wrote:
>> You'll need to do the capture card portion (but don't need to do the 
>> video source portion--though doing both doesn't hurt and may be 
>> beneficial in the future if your video source ID's aren't contiguous and 
>> starting with 1).
> I actually have only one video source, so not re-doing it looks pretty 
> safe in my case.
>> Though, really, you probably don't need to (or want to) set input 
>> priorities--you're better off just defining them in order and enabling 
>> "Avoid conflicts".
>> As I mentioned before, setting input priorities may cause your system to 
>> not record shows you want it to record...  Read section 12.6 of the 
>> HOWTO for details.
> I looked over the links you provided--thanks for bringing them to my 
> attention. I have to admit that the first one (about capture card 
> priorities) is a bit over my head. It assumes a certain basic level of 
> knowledge that I don't have and to really understand what's written there 
> I'd have to search for other literature that explains some of the concepts 
> I'm having difficulty with. But as I play around with the system, read 
> other documentation, then re-read that one, I should begin to understand 
> it better.
> One question with regard to priority settings. Given that I watch very 
> little live TV, and that I also even watch very little recorded TV (2 
> hours in any given day is the max), would you say messing with priority 
> settings could still cause me problems?

Though I didn't want to give the exact location because doing so is 
likely to make people ignore the rest of the /very important/ 
information in section 12.6, the reason you would miss shows is 
described at http://mythtv.org/docs/mythtv-HOWTO-12.html#ss12.6 in the 
paragraph starting with, "Note the two different effects."  In the event 
that Myth postpones a recording, the listings may change such that the 
later showing is not aired, meaning you can miss recordings.

Please, everyone, read the whole section if you're messing with input 
priorities, though.  (And before posting with recommendations for how to 
prevent that issue or how to "fix" Myth so that doesn't occur.  If you 
do so, you'll see that Bruce and David did an /excellent/ job of 
designing the scheduler and there are /very/ good reasons that it's 
designed how it's designed.)

> Also, if I understand correctly you're saying that setting up the cards in 
> a different order (with the better card being the first one set up), then 
> ticking the "avoid conflicts" option is going to result in the system 
> functioning pretty much like I want anyway, right? I.e., doing that is 
> going to cause the system to use the lesser card for live TV viewing and 
> the better card for recording all/most of the time in almost all 
> instances. Have I understood you correctly?

Exactly.  Which is why I've been so adamant in my recommendation that 
you not specify input priorities.

Most people who specify input priorities do so thinking it's the easiest 
way to get the configuration they want.  However, in doing so, they 
often get a more-complex configuration that is /not/ what they want 
(though appears to be on first glance).  And, since "Delete all capture 
cards" followed by re-adding cards and re-connecting inputs only takes 
only about 2 minutes on a system with multiple backends and multiple 
cards per backend--and is especially easy if you don't have to delete 
video sources (=rescan digital channels)--I contend that people should 
just do it the /right/ way, instead.  :)


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