[mythtv-users] how to resolve a suboptimal scheduling situation

Michael T. Dean mtdean at thirdcontact.com
Thu Sep 9 23:29:26 UTC 2010


  On 09/09/2010 06:24 PM, David Engel wrote:
> On Thu, Sep 09, 2010 at 04:28:26PM -0400, Brian J. Murrell wrote:
>> On Thu, 2010-09-09 at 14:58 -0500, David Engel wrote:
>>> You can use input priorities, channel priorities, the HDTV priority or
>>> power priorities.
>> I recall there being a warning not so long ago about setting priorities
>> (on tuners perhaps) that would lead to unexpected results and that that
>> should be avoided.  Is there something specific about priorities and
>> tuners that doesn't affect input, power or channel priorities?
> That's Mike Dean being cautious as adding priorities without having a
> basic understanding of them can lead to unexpected results.

Exactly.  I try to recommend that people never use channel or input 
priorities unless they've read and understand all of section 12 of the 
HOWTO ( http://www.mythtv.org/docs/mythtv-HOWTO-12.html ), because for 
nearly every single user, they don't work the way the user expects (or, 
at least, they have consequences far beyond the simplistic idea of how 
they work).

>    Since
> he's usually the first line of support on the mailing lists and irc, I
> don't try to overtly contradict him.

Though you've been taking first line on all the recent scheduler 
threads, so feel free to contradict. :)

> There is nothing special about any of the various priorities.
> Ultimately, they are all added together to come up with a single
> number for a specific program, channel, input and time.  The reason
> there are several priorities is to allow great flexibility to those
> who need it.  Note that a one time, some priorities could optionally
> be made more important than others, but that is no longer the case.
>

That being the key.  There is but one priority saying which shows to 
record.  This is basically users' "intuitive" understanding of recording 
rule priorities (which is why using them is good), but few users expect 
channel and input priorities to affect decisions of what shows record.

So while channel and input priorities do have an effect on where a 
recording may be made, they may also tell MythTV not to record something 
you want (because something you want less gets priority because of the 
non-rule priorities).  The section in the HOWTO does a wonderful job of 
explaining all the details and things you wouldn't have even thought to 
question or situations you would have forgotten about.  David, Bruce M, 
and Robert K did a wonderful job with that section.  So, read up on 
section 12, then use your new-found knowledge to make your decision 
(and, of course, feel free to ask questions, if you have any).

With a proper understanding of how the priority mechanism works (which 
David--who is a big part of the design of said mechanism--definitely 
has), and proper application of all priority types, they work exactly as 
designed.  The important part, though, is understanding how such changes 
(which are applied to all showings on a particular channel or video 
source) may affect the priorities you've specified for your rules.

Also, it's important to realize that sometimes, you may just need to 
override the scheduler's decision with a recording override because of 
how rules, priorities, schedule (including what airs concurrently as 
well as program overlap), tuner allocation, etc. line up.  In other 
words, a single prioritization scheme may not work for an entire season 
(let alone multiple different seasons).  The goal should be to 
configure--and modify--priorities as needed to minimize the frequency 
with which you have to use overrides.  Granted, that's what you're doing 
now as you prepare rules for the new season, but I thought it was worth 
mentioning, regardless.

When you boil it down to basics, if you never have to use overrides, and 
you never think the scheduler did the wrong thing, then your priorities 
are correct--regardless of how complex you may have made them (and even 
if you could have gotten the same behavior with a simpler 
configuration).  (That said, after a certain level of complexity, I lose 
interest in trying to determine what's causing specific scheduling 
decisions, so those who use complex prioritization schemes may be 
reliant on someone as patient as David to help out.)

Mike


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