[mythtv-users] prefinput for channels

[Michael T. Dean]

On 06/08/2014 08:56 AM, Eyal Lebedinsky wrote:
> I have a number of tuners, and some have problems with specific 
> channels. Don't ask.
>
> For this reason in my recording schedule I assign for each program a 
> preferred input
> that is known to be good.
>
> My problem is that I have some Title/Power schedules that can resolve 
> to any
> channel. It would be very useful to have a preferred input for each 
> channel,
> to be used when the recording schedule does not nominate one.
>
> Right now I am stuck with a "random" assignment that at times produces 
> a zero length
> recording.
>
> So, can I do this somehow? Otherwise, should this field be added?

Generally, the best way to handle, "this channel doesn't work on this 
input" (or works worse on this input) is to have different Video Sources.

A Video Source is the list of channels that are (actually--versus, 
"theoretically") available on a given input and their tuning 
information.  If different inputs have different channels available, 
they must have different Video Sources.  Or, if different inputs have 
the same channels, but they're tuned differently (either different 
frequency IDs or perhaps digital capture device versus an analog 
grabber), they must have different Video Sources.

However, you can have different Video Sources for different inputs even 
if they have identical channels available and those channels are tuned 
identically.  The reason for doing so is exactly the situation you 
describe.  This is the means MythTV provides to allow you to define 
which channels to use with which inputs.

For the below, I'm assuming you're using a modern version of MythTV 
(specifically, 0.27+).

Say you have 2 tuners.  They are both plugged into the same antenna and 
could, in theory, receive the same channels.  However, one channel 
doesn't tune well on one tuner and 5 channels don't tune well on the 
other tuner.  You would want to create 2 Video Sources.  One is missing 
one channel and the other is missing 5 channels.  Then, when you connect 
those Video Sources to the appropriate inputs (tuners, so to speak), 
MythTV would only ever use "the good tuner" for any given channel.

If, however, you happen to have 2 tuners, same antenna, same channels, 
but one channel doesn't tune well on one tuner, and 3 channels don't 
tune well and 2 other channels tune "reasonably well" on the other tuner 
(meaning in a pinch, you'd rather use that tuner than miss some show you 
could have otherwise recorded).  Then, you'd create 2 Video Sources, one 
missing one channel, the other missing 3 channels and having negative 
channel priorities on the 2 "reasonable" channels.  (So you can actually 
include the channels--even have both Video Sources with identical 
channel lists, but just have different priorities on the channels on the 
different sources.)

And note that you can have the same listings source specified for both 
(all) Video Sources.  If you were using Schedules Direct (I'm guessing 
you're not based on your e-mail address), MythTV would do caching for 
you to ensure you only download the data once.  If you're using XMLTV, 
the XMLTV grabber should handle caching for you.  If you're using 
Shepard, it /should/ (but I don't know if it does) handle caching for you.

And, with this approach, you needn't use preferred inputs on any 
recording rule and can specify rules with "any channel" (and no "this 
channel" filter) and never worry.  Remember, too, that "preferred" input 
isn't, "don't record on other inputs"--meaning with it you can still get 
zero-length, failed recordings.  So, by using Video Sources to say which 
channels are actually available on each input, you won't get 
zero-length, failed recordings.

Mike