[mythtv-users] Silly question about live tv and two tuners

[Michael T. Dean]

On 08/17/2011 11:41 AM, Ronald Frazier wrote:
> On Wed, Aug 17, 2011 at 8:29 AM, Martin Moores wrote:
>> Interesting.  I remember reading on this list about adding tuners first,
>> then virtual tuners afterwards, as Nick mentioned.  But the Wiki does indeed
>> suggest otherwise and the way it describes makes sense.
> If you only set it to 2 simultaneous recordings, then the physicals
> first/virtuals after setup makes sense. In the link I posted above,
> note the 3rd paragraph where it talks about live TV. If you setup your
> tuners in the following order
>
> Tuner 1 - Physical
> Tuner 1 - Virtual
> Tuner 2 - Physical
> Tuner 2 - Virtual
>
> the problem would be that if you enabled the "avoid conflicts in live
> tv" setting, and if you have 2 frontends watching live tv at the same
> time, then each machine is going to default to one of the last 2
> tuners, and they will end up sharing a physical tuner. If you order
> them as follows:
>
> Tuner 1 - Physical
> Tuner 2 - Physical
> Tuner 1 - Virtual
> Tuner 2 - Virtual
>
> Then you solve the live tv issue, but now you introduce the problem
> that myth won't try to use the virtual tuner for the 2nd recording.
> The better way to set it up would be
>
> Tuner 1 - Physical
> Tuner 1 - Virtual 1
> Tuner 2 - Physical
> Tuner 2 - Virtual 1
> Tuner 1 - Virtual 2
> Tuner 2 - Virtual 2
>
> This way, when recording, myth will always try to grab a tuner that's
> already tuned to the same multiplex (when possible), and live TV will
> always try to grab a tuner that's not used by another livetv session.

Good summary.

It seems a lot of people have wrongly paraphrased the approach I once 
described--heretofore known as the "Break your system by configuring 
MythTV to prefer Live TV over recordings" approach--and in so doing have 
recommended to a lot of users on other forums that they completely 
destroy their setup with alternating tuners (a "1+1" setup).

My original post is at 
http://www.gossamer-threads.com/lists/mythtv/dev/369358#369358 .  If you 
consider doing this--using the "Break your system by configuring MythTV 
to prefer Live TV over recordings" approach--you should read and 
understand the details of the entire post and use the final approach 
mentioned.  You should also bear in mind that it's best described as the 
"Break your system by configuring MythTV to prefer Live TV over 
recordings" approach.

Note that following those instructions /will/ break your configuration 
and may result in lost recordings.  However, if you truly feel that Live 
TV is more important than recordings--and that hitting a single key 
(NEXTCARD) is more work than you can bear--it's the approach you'd need 
to take.

Note also how I /never/ said to alternate tuners.  I said to configure 
/3/ tuners per card, then go back and add one to each card after.  Also, 
it assumes 3 physical capture cards.  With only 2 capture cards, it is 
guaranteed to cause problems eventually.

The alternating tuner approach will completely destroy scheduling.  
Having 2 tuners per card then adding one is better than 1+1, but still 
may cause more problems than 3+1 or 4+1.

That said, remember that MythTV--out of the box--will do the right thing 
to ensure recordings are more important than Live TV and that the "Break 
your system by configuring MythTV to prefer Live TV over recordings" 
configuration will break scheduling in some circumstances (even with a 
3+1 or 4+1 config).

The /right/ approach for Live TV users is to use the NEXTCARD binding to 
switch cards when you enter Live TV and it's locked to a multiplex and 
you want to watch something Live on another multiplex at the risk of 
losing one or more recordings.  The best approach for minimizing the 
risk is to have sufficient physical tuners that you don't have to 
worry.  If you have 10 physical tuners in your system, your risk of 
losing recordings due to Live TV is significantly smaller than if you 
have 2 physical tuners in your system--to the point that I recommend no 
one should use the "Break your system by configuring MythTV to prefer 
Live TV over recordings" approach without at least 3 physical tuners.

The /best/ approach for ensuring you can record and watch everything you 
want with the most-efficient tuner assignment is to /not/ use the "Break 
your system by configuring MythTV to prefer Live TV over recordings" and 
instead record everything you might possibly ever want to watch (with 
recording rules, not Live TV) and never use Live TV.  See, also, 
http://www.gossamer-threads.com/lists/mythtv/users/387302#387302 for 
details on why /everything/ should be a scheduled recording--even news 
and sports broadcasts.  In other words, the best approach is to use 
MythTV as a DVR--a Digital Video *Recorder*.

Remember,  the 3+1 or 4+1 approach is known as the "Break your system by 
configuring MythTV to prefer Live TV over recordings," and it does break 
it--even if you don't notice the consequences.  (But if you're going to 
use it, please at least do it right--never 1+1; 2+1 is better; 3+1 or 
4+1 is preferred; and ensure you have sufficient physical tuners (3 or 
more) to reduce the chance of lost recordings to a level you can tolerate)

Mike