[mythtv-users] Recording rankings bug...?

[Bruce Markey]

Tony Maro wrote:
> Here's one for you:
> 
> 12/21 7-9PM Charmed   rank +1
> 12/21 7-7:30PM Simpsons rank -1
> 12/21 8-8:30PM Malcom rank -1
> 12/21 8-10PM Christmas Shoes rank +2 (one time recording)

[check out "mythbackend --printsched" or "mythbackend -v schedule"]
 
> Only the last one gets recorded.
> All the rest say a program with a higher priority is scheduled.
> 
> What _should_ happen is that Simpsons gets recorded and the rest are 
> trumped.
> 
> Shoes of course would trump Charmed.  This leaves from 7-8 still open.  
> Simpsons should record.

It should but that would make the game of Tetris that the
scheduler is playing much more complex. This is a good
example because it is simply one tuner and a small number
of overlapping shows. With three more tuners, two or more
video sources and lots of shows, things get much more complex
but myth does a pretty good job. 

Currently, it works it's way forward in time. When it finds
another overlapping show it compares the currently placed one
with the next item and swaps them if the new item should win.

What happened is that Charmed won over the Simpsons then
Charmed lost to Christmas Shoes. It would have needed to go
back an revisit Simpsons again in some sort of recursive
process. The problems with that are that this might make the
scheduler significantly slower and this might lead to infinite
loops unless there was some really slick flagging.

Another approach would be to first compare all the titles in
the record list (before ever looking at any specific showings)
and sort them highest to lowest. First, place all the episodes
for the highest title for the whole period of the listings. 
Next place all of the episodes for the second title, etc. As
it got around to a lower ranked show and all cards were assigned
for the timeslot, that showing wold lose. This would have an
advantage where the first, second and third preference would go
the cards 1,2 and 3 respectively (currently only the highest
show gets the best card and the others are happenstance). The
exceptions being where cases like yours would allow Tetris to
slip a lower show onto a higher card if it fits.

In your example, Christmas Shoes would be first and win then
Charmed would lose then Simpsons would fit and win then Malcolm
would lose.

However, the scheduler currently does something slick with
multiple showing of an episode. If an earlier showing is at
the same time as other things to record but a later showing is
isolated. it will record the isolated showing even if it is
the higher ranked show in the earlier timeslot. This reduces
the crunch at crunch time and may allow recording things that
you may not otherwise get. I don't know if this could be done
as easily if it hasn't considered the possibility of lower
shows before placing.

Also, say cards 1 and 2 have cable inputs and card 1 also has
a digital cable box on s-video with sourceid 2. If I understand
the code correctly, the scheduler can determine if a showing
can be moved to another input or not. If there is a higher
ranked analog show it gets placed on card 1. If a lower ranked
digital channel show comes along, the scheduler sees that it
can move the analog show to card 2 but not the digital show so
that's what it does. Again, this wouldn't work if the highest
was strictly placed. Allowing any exceptions for swapping would
fall right back into possible infinite recursive Tetris.

> Of course I can intervene and set it the way I want, but it would have 
> been nice if Myth had figured out it didn't need to cancel all three to 
> get the one it wanted.

Assuming you're using 0.13, it is kind of a nasty situation.
Since you have 3 that lose by ranking you don't get any override
buttons to either mark Simpsons as "Record it anyway" or to mark
Charmed as "Don't record it". That sucks. You could lower the
priority for Charmed or raise the priority for The Simpsons
temporarily then change it back later (note to David and Chris,
here is a situation where it would be nice to have an easy way
to set a Single Overlap to raise the priority on this one showing
of the Simpsons).

--  bjm