[mythtv-users] prefinput for channels

Eyal Lebedinsky eyal at eyal.emu.id.au
Sun Jun 8 23:22:08 UTC 2014


On 06/09/14 08:24, Michael T. Dean wrote:
> 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

This is probably how I can handle it. However, I will need to create the Video Sources dynamically
because every boot has different problems. And I need to see if I can reliably identify these
problems in a script, because at times a channel *will* tune, slowly, and deliver a signal with
unacceptable (useless) quality. At other times it will fail to tune at all.

-- 
Eyal Lebedinsky (eyal at eyal.emu.id.au)


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