[vdr] RFE: Make VDR more friendly when using combinations of DVB-S, DVB-T and DVB-C

Mikko Tuumanen mijutu at ellipsis.fi
Sun Jun 17 16:31:36 CEST 2012

> Once version 2.0 is finished, I'm planning on dealing with the "same channel
> from multiple sources" problem.

There is a related problem with the PCTV nanostick T2-usb receiver.

The nanostick T2 can receive C/T/T2 though the same antenna connector. 
Change between C and T is done the normal way and the stick works 
perfectly with vdr as long as the setup is simple enough.

However, there seems to be no way of telling the driver or vdr whether 
the nanostick is connected to C or T antenna cable. As far as I know I 
have the following alternatives:

1) Combiner. Build a combiner to connect both signals to the nanostick at 
the same time. I guess that would require me to measure the signal levels 
and use an attenuator or aplifier to match the levels. Then I'd need to 
build some band pass circuitry to select VHF and UHF frequencies from the 
T antenna and some others from cable. I don't exactly know how to do that 
and I don't have the necessary tools to measure the signal levels. 
However, if somebody is willing to do the math and design such a combiner 
I would definetly try to build one.

2) Fix the driver. Add a kernel module parameter to the driver that can be 
used to limit the available delivery systems visible to applications. This 
solution might need some extra work if order of the usb devices change 
randomly at each boot.

3) Vdr config. Make each channel use a certain receiver in vdr. This would 
be easy, but too limiting. For example if I had 2 receivers connected to T 
and 1 to C, I wouldn't like to pin the T-channels to a dedicated receiver 
when there are more than 2 T-multiplexes in the air.

4) Make some changes to vdr? Perhaps, but I think the option 2 would be 
better idea.

Here in Turku we have some channels that are FTA-available only on DVB-C 
and a channel that is FTA-available only on DVB-T2. The driver fix 
together with a fix to the "same channel from multiple sources" would help 
greatly in this situation too.

A side note: There is a bug or feature with the nanostick that has helped 
me a lot with my setup. A DVB-T channel marked to be DVB-T2 will work just 
fine. Due to some antenna issues, I can't receive some T multiplexes with 
my old receivers, but the nanosticks can receive them ok. I have set these 
channels to be DVB-T2 in channels.conf. Vdr selects one of the nanosticks 
when they need to be received. If this "bug" didn't exist, the same setup 
wouldn't be possible.

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