[mythtv-users] 30 second early?

Michael T. Dean mtdean at thirdcontact.com
Thu Mar 22 07:34:22 UTC 2012


On 03/21/2012 07:12 PM, Ross Boylan wrote:
> On Wed, Mar 21, 2012 at 12:43 PM, Michael T. Dean wrote:
>> ......
>>
>> Actually, the scheduler completely ignores the global:
>>
>> Time to record before start of show (secs)
>> This global setting allows the recorder to start before the scheduled
>> start time. It does not affect the scheduler. It is ignored when two
>> shows have been scheduled without enough time in between.
>>
>> and
>>
>> Time to record past end of show (secs)
>> This global setting allows the recorder to record beyond the scheduled
>> end time. It does not affect the scheduler. It is ignored when two shows
>> have been scheduled without enough time in between.
>>
>> The "recorder" may use them.
>>
>>> I'm using that, but I've seen one statement that these times don't
>>> control recording start at all, but only system power-up before
>>> recording.
>> Yeah, basically.  The "Time to record before start.." applies only to
>> first use of a tuner and "Time to record past end..." applies only to
>> last use of a tuner in a string of back-to-back recordings with that
>> tuner.  I.e. it's little more than a placebo and (as you said) should
>> never be expected on any recording.  If you want to record extra, you
>> should tell the scheduler to schedule that time and have sufficient
>> tuners to record what you want.
> Thanks for the info.  I had not understood the distinction between
> scheduled times and actual recording times.  So if I'm understanding, the
> globals will actually start recording (not just power up the system) early
> or continuing late provided doing so does not cause overlap with other
> recordings.  Right?

When tuner 1 becomes active for an 8:00-8:30 recording, the recorder 
will start the 45 seconds early for the "Time to record before start..." 
setting.  It will continue recording until 8:30, then it will start the 
next recording from 8:30-9:00 /without/ using the extra 30 seconds on 
the end of the first recording for the "Time to record past end..." 
setting or the 45 seconds at the beginning of the second recording for 
the "Time to record before start..." setting.  It continues like this 
through the 9:00-9:30 and 9:30-10:00 shows, then at the end of the 
10:00-11:00 show, it records an extra 30 seconds on the end of that 
final recording.

Note that it did all of this and never once used Tuner 2 or Tuner 3 or 
Tuner 4, because Tuner 1 was the most-preferred/best tuner, so it tried 
to keep all recordings on Tuner 1.  Note, also, that had it recorded the 
8:30-9:00 show on Tuner 2, it could have put the 30s on the end of the 
first recording and the 45s on the beginning of the second 
recording--without causing a conflict (and continued throughout the 
night like that).  But, it didn't do that.  So it actually did not start 
recording early or continue late, even though it could have done so 
without causing overlap with other recordings.  It did not record extra 
before or after the shows because it wasn't told to--the only way to 
tell it to record extra is to use the per-recording-rule start early/end 
late settings to actually inform the scheduler that it needs to record 
early or late.

So, this means that in 5 recordings, one started 45s early and one ended 
30s late at "sign on" and "sign off" of Primetime, when all the 
recordings for today were done.  That's 20% (1/5) of tonight's shows 
getting the 45s extra on the beginning and 20% getting the 30s on the 
end.  Even in baseball, those aren't good numbers.  ;)

In other words, all those numbers really did for me was make me feel 
like it /might/ just get the beginning.  Of course, the user thinks what 
happened was, "Oh, I see I missed a tiny bit of the beginning of 30 
Rock.  Stupid NBC.  They must have started 50s early because of my 45s 
global 'Time to record before start...' setting," when in fact the show 
started 5s early* and MythTV did not use the 45s "Time to record before 
start..."  However, the user feels all shiny because, "MythTV and I 
tried our best, but what can you do when NBC doesn't cooperate," so the 
placebo works (and, because some feel it's useful, we're stuck with it, 
and users miss out on the beginning/end of some shows because they don't 
properly schedule them).

Note, also, there are various settings that can affect placement of 
recordings in such a way as to improve the chances of getting the "Time 
to record before start..." and "Time to record past end...", but using 
them messes with the scheduler (and can actually increase the likelihood 
of conflicts by causing the scheduler to paint itself into a corner to 
try to get you your "only if you can without causing a conflict" few 
extra seconds on the beginning or end).  And, various combinations of 
these settings can have very complex effects on scheduling.  So, messing 
with these settings can be like mixing non-placebo drugs--and may result 
in problems.  (This paragraph is my, "I realize there's a lot more to 
it, including things you can do to change the effects described above, 
but I've already written so much that no one will actually read this 
far, so it's definitely not worth talking about the rest and why you're 
better off with the default behavior, that's described above" disclaimer. :)

As far as the "power up" thing goes, that was probably a reference to 
HDD spin up or STB channel change script or similar.  This post gives a 
pretty good description of the history of these options: 
http://www.gossamer-threads.com/lists/mythtv/dev/150095#150095 
(and--ignoring the quoted message--the portion up through, "What 
concerns me here" is still a good description of what the 2 different 
settings are for and how they're meant to be used).

Mike

*Or, quite possibly, 30 Rock started /exactly/ (like to the second) on 
time.  However, MythTV told my recorder to stop recording Community at 
its end time (8:30--which is right when 30 Rock was starting), then 
waited 2s to give the encoder link time to stop the current recording, 
at which point it started up a new recorder for 30 Rock and began 
writing data once it received a keyframe--so I miss the first few 
seconds of 30 Rock.  However, because I know that it will just be a 
couple of pictures of NYC scenery and Liz walking a step or two before 
saying something, I've decided not to do a 1-min /scheduled/ start early 
for that show.  At least it worked about like this in 2004 ( 
http://www.gossamer-threads.com/lists/mythtv/dev/21068#21068 )--some 
details and/or numbers may have changed in the interim, but it still 
gives a pretty good description of why there's "missing time" between 
back-to-back recordings (and this applies whether they're on the same 
channel or not).



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