[mythtv-users] multiple sources with overlapping channels

Nick Morrott knowledgejunkie at gmail.com
Mon Dec 11 21:25:16 UTC 2006

On 11/12/06, Robin Neatherway <robthebob at gmail.com> wrote:

> > 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 the data is coming from a source using the uk_rt XMLTV grabber, you
could use the Perl http cache utility to cache listings downloads from
the RadioTimes website in-between successive mythfilldatabase runs.
Only new and updated channel data should be downloaded.

I wish I had a while ago was that MFDB (when run manually) could use a
single comprehensive uk_rt XML output file containing listings for all
configured video sources and  apply this data against only channels
that actually exist on the sources it is being applied against, as
opposed to creating new channels etc. Last time I tried this, it
wasn't possible, and therefore I had been running MFDB manually, once
of each video source.

I also want to know whether it is yet possible to apply EIT data
against non-EIT sources, such as being able to use DVB EIT radio
channel data on a predominantly uk_rt-based cable video source for
channels that are not covered. I had been running both the uk_rt
grabber and tv_grab_dvb application manually to allow me to apply a
mixture of program listings data against a single video source
containing channels that could not be populated with data from a
single grabber.

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

Whenever channels are assigned identical callsigns, I also ensure that
they are receiving the same listings data. I do this using the uk_rt
grabber for all common DVB-T and ntl: cable channels I have
configured, which gives the scheduler the most flexibility in being
able to match programs across sources.

This also makes the point about which source's data is being displayed
moot, as the data is the same on all common channels.

If you use different listings data for channels having the same
callsigns (e.g. uk_rt for cable, and DVB EIT for OTA), you cannot
guarantee the scheduler will be able to intelligently schedule
recordings across capture cards as the listings data itself may not

> Does matching the callsigns leave you with two entries for a
> particular channel, but allow Myth to realise that programs you have
> set to record on that channel to record on any channel with a matched
> callsign?

All configured channels remain for MythTV to schedule recordings with,
until you remove them in the channel editor. Channels having identical
callsigns enable MythTV to treat such channels as identical for
scheduling purposes - MythTV can and will record from any  instance of
the same channel. However, which of these channels the scheduler
chooses to record from is down to how you have set your source,
channel, and individual recording rule priorities.

My UK-based setup has all common channels available on ntl, DVB-T and
analogue having the same channel numbers (using ntl's numbering
scheme), same callsigns, and same names. DVB channels have top
priority, ntl second, and analogue lowest priority. Channels which are
flaky on DVB have raised priorities to give their ntl-based
counterparts preference in the scheduler.

This has worked well since 2004, and only recently, having moved over
to the card-hogging automated EIT data downloads, have the quirks I
mention above caused me to scratch my head.


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