[mythtv-users] HD simulcast: how best to configure

Michael T. Dean mtdean at thirdcontact.com
Fri Jun 14 14:14:28 UTC 2013


On 06/14/2013 09:32 AM, Joseph Fry wrote:
>> I'm currently setting up MythTV, but I'm struggling a bit with how to
>> configure my channels:
>>
>>  From what I've learned so far (please correct me if I'm wrong):
>>
>> * If two channels have the same Callsign, Myth assumes they're equal

... for purposes of recording from rules.  Specifically, any "this 
channel" filter will match any channel with the same call sign.

>> * If two channels have the same channum as well, Myth collapses them into
>> 1 channel, choosing a free tuner when needed.

More precisely, they're still distinct channels, but they're shown only 
once on the guide if all of channel call sign /and/ channel number /and/ 
content are the same.  (Though if the channels' content are not 
"substantially identical", you should /never/ give them the same call 
sign.  IMHO, if the content ever differs, you're better off using 
different call signs.)

Really, the only purpose for a channel number is to provide a way to 
quickly tune that channel in Live TV by typing the number.  In the case 
of channels with the same call sign, the channel number takes on an 
overloaded meaning as a hint to show only one row to represent all the 
channels with that call sign and channel number, because they're 
completely equivalent for the purposes of recording (call sign) and Live 
TV (typing the channel number will tune any one of the channels).

If you want to be able to treat the channels differently, you need to 
differentiate their call signs and/or channel numbers.  If you want to 
be able to tune a specific channel in Live TV, use different channel 
numbers.  If you want to be able to record a show only from a specific 
channel, use different call signs and "this channel" filters.

And note that channel number is /completely/ user-specifiable.  It need 
not correspond to the channel number used by the provider.  So, for 
example, when the stupid cable company in this area calls "Fox 35" 
channel 3, I can renumber it to 35, as it's meant to be.

That said, you may need to ensure that every single channel on a given 
Video Source has a distinct channel number.  There were (are?) some 
issues in the code where having the same channel number on multiple 
channels on the same Video Source may cause problems.

>> I receive a certain channel in 3 ways: Once via DVB-T in SD, once via
>> DVB-S in SD and once via DVB-S(2) in HD. The content of these three
>> channels is identical, only the quality differs (there is also a
>> difference in bitrate between the SD streams).
>>
>> What is the best practice to merge these channels?
>>
>> * Combine both SD's, and keep HD as a different channum and/or callsign?
>>
>> * Combine all 3. Can I assign priorities to channels, so that I preferable
>> watch/record HD, only falling back if scheduling requires me to?

While you can use priorities, I recommend you instead use:

> You can combine all 3 channels and simply adjust the order in which myth
> uses its tuners.

... by specifying Schedule Order (and Live TV Order) in mythtv-setup.  
When 0.27 is released, using priority will be fine--as it will do what 
you expect (and won't record lower-priority shows and skip 
higher-priority shows just because the bad shows air on HDTV channels).  
In 0.26 and below, channel priority can result in conflicts/missed 
recordings of preferred shows, so shouldn't be used unless you really 
understand how it works (or are willing to miss shows you like and/or 
manually monitor the upcoming recordings very closely).

> Typically, I would combine the SD only sources into one channel... one that
> almost never gets watched or recorded.  And put the HD channel as it's own
> number.
>
> However if your two SD sources are noticeably different in quality I may
> consider having three distinct channels, perhaps the HD would get a
> standard channel number (10) while the two SD sources would get a dotted
> number (10.1, 10.2).  This would be particularly beneficial if there is any
> chance that the 3 channels would have slightly different programming.
>
> Honestly it's entirely up to you.  I know that here in the States I can get
> separate guide data for the HD channels, so it's a no-brainer.  This way I
> can create rules that say I want to record a particular show in HD only,
> and another show in SD only.

This is the ideal approach.  If you have good guide data that 
differentiates between HDTV and SDTV content, use that to ensure you get 
HDTV when you want it.

Mike


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