[mythtvnz] Overlapped recordings on ivtv cards?

[Dr. David J. Knowles]

Nick Rout wrote:
> On Mon, Nov 23, 2009 at 3:35 AM, Stephen Worthington
> <stephen_agent at jsw.gen.nz> wrote:
>   
>> On Sun, 22 Nov 2009 23:27:59 +1000, you wrote:
>>
>>     
>>> 2009/11/22 Stephen Worthington <stephen_agent at jsw.gen.nz>
>>>
>>>       
>>>> I like to have 1 minute of pre-roll on some of my Sky recordings, so
>>>> that I do not miss the beginnings of programs, and usually at least 1
>>>> minute of post-roll too so as not to miss the endings.  That is
>>>> causing problems as I only have one S-Video input from my PVR-500 ivtv
>>>> card connected to my Sky decoder, and it seems that MythTV is not
>>>> recording both programs when the pre/post roll causes overlapped
>>>> times.
>>>>         
>>> If you set the pre/post-roll in the setup (Settings -> Setup -> TV Settings
>>> -> General -> General (Advance) as opposed to setting them for a specific
>>> recording and two shows go head-to-toe, MythTV is cleaver enough to start
>>> and stop the show on time, and not record the pre/post-roll.
>>>
>>> If you set the pre/post-roll for the actual recording, then MythTV will
>>> enforce that the pre/post-roll be recorded, and consider it a conflict (and
>>> based on your rules not record one show)
>>>
>>>
>>>       
>>>>  It would be nice if I could just get it to record two programs
>>>> at the same time when there is overlap.  Is there some setup somewhere
>>>> that I have missed that will make this work?  Would going into the
>>>> database manually and setting the option for multirec to 2 work?
>>>>
>>>>         
>>> That won't work. See below.
>>>
>>>
>>>       
>>>> I guess I could get a second SCART cable and connect the second
>>>> PVR-500 tuner, since it is not used for anything, but SCART cables are
>>>> expensive.  Can you get Sky to give you a second one?
>>>>
>>>>         
>>> That unfortunately won't work since the Sky decoder can only show one
>>> channel at a time. A second scart cable will only mean that you will one
>>> show twice. The only way around this is to rent a second Sky decoder.
>>>
>>>  -- simon
>>>       
>> You are absolutely right, in the general case.  But what I completely
>> failed to explain is that I am dealing with two programs that are back
>> to back on the same Sky channel (two episodes of Mythbusters).  Since
>> the channel does not have to be changed, there is no reason that
>> MythTV could not record the pre- and post-roll for both programs, and
>> that is exactly what happens on DVB-T with multirec enabled.  I will
>> have to have a look at how multirec is implemented and see if it would
>> work with an ivtv input.
>>     
>
> multirec does not work on analogue recorders.
>
>
>   
As Nick said multirec will not work on analogue decoders as it uses the 
virtual tuners to perform
multirec. It is also sensitive to hard versus soft time padding.

This is something I recorded when I was messing with multirec (see 
below). Short answer
hard padding will always cause a shift to a new tuner if the times 
overlap. Soft padding is
ignored if two adjacent programs are recorded. This allows the same 
tuner to be used for
both with a brief pause while the card tuner resets exactly at the 
boundary. It sounds like
you have hard padding set when you should have soft.

Multirec uses a DVB card to record multiple simultaneous channels on a 
single multiplex.

It can also be used to force adjacent programs on the same channel to 
record with an overlap
i.e. avoiding the end of a program being on the following recording and 
vice versa. It is not
however obvious how to get it to do this.

Before you can set up adjacent programs to record completely you must 
understand the
concepts of soft and hard padding.

Padding is the adding of recording before or after the program actually 
is scheduled.
This catches the situation where programs run early or late. A common 
padding is 5m
before and 10m after a recording.

Soft padding is a global setting (set in Setup->TV 
Settings->General->Advanced).
In this page you can set before recording time and after recording time 
values. Soft padding
is added onto all programs recorded IF POSSIBLE. If the padding is not 
possible it is ignored.
One example of soft padding being ignored is for adjacent recordings. 
Adjacent recordings
stop at the moment the scheduled program ends. This leads to the 
problems with the end
of programs appearing on the next recording.

Hard padding is a part of the scheduling of a program. Under Scheduling 
Options you can Start
recording N minutes early or End recording N minutes late. In effect the 
hard padding is added
to the scheduled duration of the program. Hard padding is always used by 
the scheduler when
working out the recordings. For this reason it can cause conflicts as a 
single channel can no
longer be used for two programs back to back on a single channel.

With Multirec multiple channels is less of an issue. This can be used to 
fix the overlap problem
of adjacent programs. Two adjacent programs with hard padding will 
automatically record
on two channels. This fixes the overlap because the soft padding will 
then apply because the
programs are on different channels.

To fix the overlap add a minute to the beginning and end of a program. 
This will get the
programs to record properly.

This can be set as a default for all new recording rules by setting the 
values in
Setup->TV Settings->Recording Priorities->Set Recording Priorities. 
Default "Start Early" and
"End Late" values. This will not alter any existing recording rules.



> ------------------------------------------------------------------------
> Dr. David J. Knowles  <dknowles at clearfield.com> Senior Systems Architect
> Phone (+64 9)  358 2081                          Clearfield Software Ltd
> Fax   (+64 9)  358 2083                    1st Floor 8-10 Whitaker Place
> Mob   (+64 21) 75 9090                P O Box 3901 Auckland, New Zealand
> ------------------------------------------------------------------------
>
>
>   
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