[mythtv-users] multiple sources with overlapping channels

Bruce Markey bjm at lvcm.com
Tue Dec 12 20:09:34 UTC 2006

Robin Neatherway wrote:
>> You need to create a different video source for each provider or
>> service that has a different set of channels. Each input with a
>> connection to that service should be associated with the video
>> source for that service so the system will know which set of
>> channels are available for each of your active inputs.
>> For example, this user also has one digital cable set top box. The
>> digital cable service carries channels that are not available over
>> basic cable. The user would create another source called "Digital".
>> This set top box is connected to the second card by s-video so under
>> "Input connections", "Digital" is associated with the s-video input
>> of card 2. The system would then know that programs on channels from
>> the Digital source can only be recorded from this input. Further,
>> the scheduler understands that it can only record one show at a time
>> from card 2 so it can assign Cable or Digital shows to the card but
>> not both at the same time.
>> Some TV stations may be broadcast over a channel from the Cable
>> source and also broadcast over a channel from the Digital source.
>> Note that two channels carrying the same primary station may not
>> have the same TV listings due to carrying the primary station part
>> time, including local programming exclusive to one of the channels,
>> the channels may be in different timezones, etc. Listings
>> information must be associated with each channel even if two or
>> more channels report that they carry the same station.
> I see here that I should have two video sources, one for the analogue
> and one for the digital input.


> I wonder though, surely this would
> result in a lot of duplicate data being downloaded?

If you are grabbing listings from the same web site, it would
grab the same data twice and that adds to the confusion between
channels and stations. You need to have an entry in the channel
table for BBC2 that is associated with the analogue source, it's
tuning information and picture settings then another for BBC2
from DVB. Each of these rows have a different 'chanid'. The
program table needs to have entries for the programs available
from each of these chanids.

In your case, the listings for these two channels are identical
but that is not universally true. I get KVBC on cable channel 3
and digital cable 123.

mysql> select chanid,channum,callsign,xmltvid from channel where callsign='KVBC';
| chanid | channum | callsign | xmltvid |
|   1003 | 3       | KVBC     | 10790   |
|   2123 | 123     | KVBC     | 21661   |
2 rows in set (0.00 sec)

Notice that the (poorly named) xmltvid has a different ID number
from Data Direct. Channel 123 has a local politics public
service show that is not on the basic cable channel and shows
that are broadcast in HDTV have the program.hdtv flag set even
though the other info is identical for the same programid as
the showing on channel 3.

Another example of the difference between channels and stations.
"CNN" in Atlanta, GA broadcasts "Anderson Cooper 360" at 3:00UCT.
When I tune to channel 20 at 7pm I see Anderson Cooper. At the
same time, someone in Ohio is seeing him on channel 53 at 10pm.
Listings for "CNN" don't get the job done. I need listings for
Cox Cable channel 20 in Las Vegas, NV which primarily carries
"CNN". You may note that the US standard of numbers assigned to
frequencies is different than your TVs where you preset a number
to a frequency but that's not the point. If your DVB service
carried CNN, the times and listings would be different than
Atlanta, Cleveland, or Las Vegas. You could even potentially
have an analogue CNN from a different service with slightly
(or significantly) different listings.

>> <sect2>Matching Callsigns
>> <p>
>> If a recording rule is a type that can record from any channel, "The
>> Apprentice" would match for any channel that shows episodes which
>> may include CNBC or BRAVO. However, for Single, Timeslot. Weekslot
>> or Channel rules, "The Apprentice" would only match showings on the
>> selected station. For example, KVBC is an NBC affiliate on channel
>> 3. Channel 733 is KVBCDT which is HDTV over cable from the same
>> station. If a Single record rule was set for "The Apprentice" on
>> channel 3, it could not record this showing from 733. If 733 was
>> chosen, channel 3 could not be used to record.
>> However, the "Channel Editor" in mythtv-setup can be used to
>> change the "Callsign" for channel 733 to be "KVBC" also, MythTV
>> would then understand that both of these channels are from the same
>> broadcast station. Assuming the HDTV input was input number "1",
>> "The Apprentice" would record on 733. If, however, this digital
>> input already had a higher priority show assigned to it in that time
>> slot, "The Apprentice" would be assigned to KVBC channel 3 on input
>> 2.
> Ok, so if in my case I have the digital and analogue BBC2's, which are
> in fact exactly the same channel, how should I make them show up as

s/channel/station/ . Each if these are different frequencies
from a different wire on different input. Both carry programing
from the BBC2 broadcast center.

> just a single entry in the EPG? With matched callsigns, I still get

People used to complain about seeing the same channel number
and callsign in two rows next to each other. The rule now is
that if the channum and callsign are identical, only one row
is shown. I see 3 KVBC and further down, 123 KVBC. If I had
another source with KRAP on channel 3, I'd see "3 KVBC" then
"3 KRAP". If I included channel 3 in my digital cable source
I would still see just one "3 KVBC".

> two separate entries, but with matched numbers I understandably get
> only one entry (albeit with the strange showing the top channel
> behaviour currently), but which video source would it be using to show
> program information there and should that only really be used for
> inputs that are receiving exactly the same set of channels?

If, as in the example above, I included channel 3 in my digital
cable source, when I press "R" to record a show from "3 KVBC",
it doesn't matter if that data came from chanid 1003 or 2003
because the scheduler will decide which source/channel/input is
the best choice to record this KVBC show. The main thrust of the
HOWTO section is an attempt to explain the different way you
can influence the preferred choice. Which "3 KVBC" program table
entry is used for the EPG display is not part of the decision
making process.

> Does matching the callsigns leave you with two entries for a
> particular channel, but allow Myth to realise that programs you have

s/channel/station/ . There are two channels (frequencies) but
if the callsign AND channum match, the EPG will show a single
row for that combination.

> set to record on that channel to record on any channel with a matched
> callsign?

Yes. If the callsigns match (regardless of the channum) the
scheduler considers them to be from the same station (building).
When a BBC2 show is requested, it will try to record from DVB
assuming DVB is preferred. If the DVB input is busy, it can
fail over to the analogue channel that carries BBC2 and has a
listings entry for the same episode.

So, I guess I need to add some information about how the EPG and
program list pages display things when two or more channels
have the same callsign.

--  bjm

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