Understanding how EPG update works for merged DVB-T and DVB-S channels

[zer]

I'm in the UK and have both DVB-T (Freeview) and DVB-S (Freesat) tuners.  DVB-T EPG update works pretty well but DVB-S is flaky...

When I first scanned for channels on the DVB-S tuner and did an EPG update, only the currently showing and next programs were populated.  I had to manually set all the channels EPG source "Freesat (UK)", after which I got a full set of guide data for 7 days for most if not all of the channels.

Shortly after this and also setting up the DVB-T channels, I used auto-merge such that most of my channels now have both a DVB-T and DVB-S source.  At some point since then, I've noticed that most of the channels that are only available on DVB-S are no longer getting any guide data.

For the merged channels, its not really clear which tuner is now being used to obtain the EPG data - in the web UI channel settings shows most of the channels with their DVB-S (Freesat) info but I don't believe DVB-S is actually being used - I split one of the channels and found DVB-S one didn't have any guide data even after a subsequent EPG update.  Also in the database it appears that only one epg_source and epg_mapping column value is retained when merging (CHANNEL table), the original values aren't restored if you later split the channel.

I would like to understand the following (maybe it is documented somewhere?):

1. For DVB-S channels, what's the difference in selecting 'DVB/ATSC EPG' vs 'Freesat (UK)'?  How is the EPG data obtained?
   
2. For merged DVB-T and DVB-S channels which capture source is used for the EPG update?  Both?  Arbitrary?  The one specified in the epg columns of CHANNEL?
   
3. If I split a merged channel should I not expect EPG data to work on all sources of the channel?
   
4. Is the value of epg_mapping in the DB relevant or important at all?  I have some DVB-S only channels that have EPG data even with nothing in this column, others that don't have EPG data with something in that column, etc...
   

Any and all information welcomed, just like to understand how it all works in the hope I can fix the channels with no guide data without having to "start over" with re-tuning!

[sub]

For DVB-S channels, what's the difference in selecting 'DVB/ATSC EPG' vs 'Freesat (UK)'?  How is the EPG data obtained?

These two EPG options are pretty much the same. The differences is that the Freesat EPG is all carried on one specified frequency, unlike other DVB setups where the EPG is carried on each frequency containing channels.

For merged DVB-T and DVB-S channels which capture source is used for the EPG update?  Both?  Arbitrary?  The one specified in the epg columns of CHANNEL?

It would have chose the device nearer to the top of the list master channel, and would have retained whatever EPG settings it had. If you've got some channels unique to DVB-T or DVB-S, they'd stay on whatever they were using.

If I split a merged channel should I not expect EPG data to work on all sources of the channel?

Hopefully it would have EPG on all after an EPG Update. (I don't have the Freesat EPG here in NZ, so haven't done a whole lot of testing around some of these scenarios.

Is the value of epg_mapping in the DB relevant or important at all? 

Yes. It's more important for other EPG sources such as xmltv or schedules direct. From memory it doesn't contain much for freesat/dvbepg.

[zer]

Thanks for the info sub. Examples of epg_mapping values for DVB-T and DVB-S below, I guess when using the Freesat (UK) option, this info is not required. Even so I feel like I'm going to have to try deleting some of the channels that have no guide data and rescanning & setting them up again to see if that fixes things...

(DVB-S)
<epg>
<source>DVB/ATSC EPG</source>
<capture_source>26</capture_source>
<readable_source>53310:2110:2 Sony Action</readable_source>
<mapping>53310:2110:2</mapping>
</epg>

(DVB-T):
<epg>
<source>DVB/ATSC EPG</source>
<capture_source>23</capture_source>
<mapping>8442:8197:9018</mapping>
</epg>

[Graham]

Thanks for the info sub.  Examples of epg_mapping values for DVB-T and DVB-S below, I guess when using the Freesat (UK) option, this info is not required.  Even so I feel like I'm going to have to try deleting some of the channels that have no guide data and rescanning & setting them up again to see if that fixes things...

Have you tried setting the EPG source to None, rebooting (to restart NextPVR) and then setting the EPG to DVBT or DVBS as requiried ... that might avoid the neeed for deleting the channel.