[mythtv-users] Input priority

[Michael T. Dean]

On 01/20/2010 05:14 PM, Kevin Ross wrote:

> Michael T. Dean wrote:
>
>> People generally change channel and input priorities thinking
>> they're affecting which channel or which input is preferred, but
>> they're actually affecting which shows are recorded.
>
> This is at odds with the documentation.  From
> http://www.mythtv.org/docs/mythtv-HOWTO-12.html, in the section
> about Input Priority:
>
>
>
> "If you have multiple cards of different quality, you may want to
> set input priority to encourage the scheduler to record shows on
> your best card(s) whenever possible. This can also be useful if you
> have multiple video sources which include the same stations. For
> example, with digital and analog cable you could increase the digital
> cable input preference by 1 to tell the scheduler that you want to
> record from the digital channel whenever possible but the channel on
> the analog input could still be used when the digital input is
> busy."
>
>
>
> Is this just a case of the documentation either being wrong or
> misleading? Or is my understanding wrong, you are both saying the
> same thing, just different ways?
>

It's just a case of there being a lot more to the documentation:

The short story:  it says, "you may want to," but then the rest of the
document describes the result--and should convince you that you don't
want to except in rare circumstances where you have a truly horrid input...

The longer (but still not complete) story:

-----
Order of Inputs

By default the scheduler chooses the first (lowest numbered) input which
has a showing of the scheduled program as it fills the schedule. If a
lower priority show is on at the same time as a higher priority show
that has been assigned to input 1, then input 2 will be used next and so
on. Therefore, configure your best card and input first and next best
card and input second. There may be differences in the type or brand of
capture card, signal quality from the cable, system resources such as
disk space, CPU, etc. By configuring your best input first, more
recordings, and your highest priority recordings, will use that input.

A common situation is that a newer and better card is added last. For
example, you may initially setup your system with two analog cable cards
and then add a HDTV card. If NBC is on a cable channel and "The
Apprentice" is shown in HDTV on an NBC HD channel, the scheduler would
still prefer analog inputs 1 and 2 over the new HD input 3.

So, if you'd like the scheduler to prefer a new source, the simplest
thing is to run mythtv-setup and "Delete all capture cards" then enter
your cards and inputs in your preferred order. This will not remove your
sources and channels - you want to keep those and only renumber your
cards and inputs. In this example, once the changes have been made and
the Master Backend is restarted, the scheduler would then choose "The
Apprentice" in HD on the new input 1 and only use the analog inputs (now
numbered 2 and 3) when the HDTV input was occupied with another show.
----

as well as all of section 12.6 "Scheduling with more than one Input",
including the subsection, "Input Priority," which shows the effect of
setting input priorities, and the, "Reschedule Higher Priorities,"
portion of section 12.2 "Scheduling Options," which discusses the
implications and possible consequences of that effect.

Remember that priority says how much you want to record an episode, and
there is only one priority in the end, so it's not "just" determining
where you want to record or from what channel.  True, it will have an
effect on where/what channel, but it has a far greater effect on whether
or not something is recorded--especially when you realize that the
schedule you get from your listings provider is not absolute and can
change between the time the recording decision is made and when the show
you wanted to record was *supposed to* air.

Mike