(DVB-T2) channel selection logic on program restart or start of recording

[hostalp]

Hello,

I've got 2 DVB-T2 transponders (frequencies) of the same provider available.

Channels are identical on both, all IDs (network ID, stream ID; channel video PIDs, audio PIDs, service IDs, PMT IDs, PCR IDs - for the same channels) are identical.

 

When I select any channel from the 2nd transponder that is stored with higher DVBViewer channel numbers than the 1st one, exit DVBViewer and launch it again, I end up at the same channel, but on the 1st transponder (stored with lower DVBViewer channel numbers) instead of the 2nd one.

 

The same happens when I select recording of something from the 2nd transponder: it will start recording on the same channel from the 1st transponder instead.

 

And the same happens when I use the "Last Channel" option to switch back to the channel on the 2nd transponder: I end up at the same channel on the 1st transponder instead.

 

Could this be fixed?

 

DVBViewer 7.0.1.2

[Griga]

vor 4 Stunden schrieb hostalp:

Could this be fixed?

 

You can help DVBViewer to distinguish the channels by performing the following steps:

• Open TV/Radio -> Channel Editor, right-click the root folder or category where the channels of the second transponder in question are located, and export it as INI file.
• Open the INI file with a text editor. Search & replace OrbitalPos=5000 by OrbitalPos=5001. Additionally you should use search & replace to change the root folder or category name (Root=... or Category=... in the INI file) to something that helps to identify the modified channels.
• Save the changes and use drag & drop to re-import the INI file into the Channel Editor.
• Switch over to one of the modified channels. You will see that DVBViewer is able to distinguish it clearly from the same channel on the first transponder. Additionally you can see on the "Reception Settings" page of the Channel Editor (click the gear wheel) that a new entry named "DVB-T No.1" shows up in the list of available reception types.

Technical explanation: Of course terrestrial antennas are not directed to an orbital position like satellite dishes. However, DVBViewer stores this parameter as pseudo orbital position also for DVB-T (500.0°) and DVB-C channels (400.0°), on one hand for internal consistency across different DVB networks, on the other hand as possibility to distinguish DVB-T/C networks that cannot be distinguished by other means.

 

So if some of your channels are flagged with 5000 and others with 5001, they internally belong to different DVB-T networks, like satellite channels from different satellite positions, e.g. Astra and Hotbird. Since the (pseudo) orbital position is a "must match" part of the channel ID, DVBViewer will always regard channels with different orbital position as different and will be able to recognize them unambiguously, even if all other parameters are the same.

 

If you have to deal with it frequently, you may also want to use TransEdit (see members download area). The scanner and transponder list editor tool is able to flag DVB-T/C transponder lists and scan results with a Network Number ("Net No." input line in the main window). This number is the offset relative to the base orbital value for the reception type. In your case 5001 corresponds to Net No. = 1, 5002 would be Net No. = 2 etc.

 

[hostalp]

Hello,

thanks for the tip, it really helped.

 

Would it be possible to modify the DVBViewer to assign unique orbital position values in such cases (during the channel search) instead of constant pseudo values 5000 or 4000? It would be more straightforward then.

 

I acknowledge there should be some logic behind generating the orbital position value (in order to get consistent, predictable and repeatable results) such as deriving it from the frequency & network ID or so...

Edited January 9, 2021 by hostalp

[hostalp]

Also I noticed that even after this change (setting unique positions) there's still 1 entry per each channel in the EPG Window so when switch to some channel or setup recording via the EPG window it will still use the 1st transponder (the 2nd isn't shown there at all).

[Griga]

vor einer Stunde schrieb hostalp:

Also I noticed that even after this change (setting unique positions) there's still 1 entry per each channel in the EPG Window so when switch to some channel or setup recording via the EPG window it will still use the 1st transponder

 

That's in the nature of things. The EPG <--> channel assignment is based on the Network ID -> Transportstream ID -> Service ID path (according to the DVB specifications, DVBViewer additionally uses the reception type DVB-S/T/C). So for two channels with identical ID values and the same reception type a single set of EPG data is stored, and the EPG --> channel relation is ambiguous.

 

You can also put it like this: Incoming EPG data only specifies the Network ID -> Transportstream ID -> Service ID path for indicating to which channel it belongs. Since the EPG may contain data for different channels, transponders and even networks in a single stream (EIT, Event Information Table with PID 18), your two transponders can't be distinguished from the EPG point of view.

 

[hostalp]

I see. That's quite unfortunate.

If you're bored enough you may try to come up with some workaround such as "restrict the EPG data to this transponder" option (in the channel editor) that would restrict the EPG data received via certain trainsponder only to its channels.

However that would require some adiditional logic to handle this properly (to avoid conflicts with the EPG data for the same channels from other transponders) and the userbase that would benefit from that would be probably small so it may be not worth the effort.