[linux-dvb] Re: AW: How to write my own .dvbrc-File?

[Dave Chapman <dave@dchapman.com>]

On Monday 30 April 2001  8:11 am, Hakenes Rolf wrote:
> But as far as I know (I'm not a user of VDR) this ID is not
> really needed to correctly tune a channel. For this you only need
> Frequency, Polarisation, SymbolRate, ServicePID, AudioPID and VideoPID. To
> get this, you can either look into the PID-tables at www.lyngsat.com, or
> use a scanning program (which is not really on the market now for linux,
> AFAIK, but there are some for Windoze).

It's slightly simpler than that - you don't need the ServiceID (at least, 
I've found no way of telling the driver what the ServiceID is for a channel). 
You also need the teletext PID if you want teletext.

Regarding scanning, the DVB specifications allow a transponder stream to 
include information (frequency, polarity, symbol rate and orbital position) 
of other transponders on both the same satellite, and others.  In my 
experience, this is only used on the major satellites (the two Astra 
positions, Hotbird, and I think 1W), so it is not a solution for everyone.

So there are two ways to scan a satellite (depending on the quality of the 
service information it transmits):

a) starting at a known transponder frequency and then recursively scanning 
the transponders mentioned there, 

b) a "traditional" frequency scan using a list of potential symbol rates (the 
tuner in the Siemens/Hauppauge cards is very reluctant to lock onto a signal 
if you don't specify the right symbol rate).

I read somewhere that all commercial digital satellite receivers just perform 
the first type of scan - none of them include an "analogue-style" frequency 
scan (there are one or two exceptions though).

I am working on both types of scanning, and hope to find time to release 
something that performs scan (a) quite soon.  This will output the 
transponder data in XML, and I'll include a filter to convert this XML into 
VDR's format (and possibly dvbrc, but I don't use that format myself0.  

There is also a program "stest" in the libdvb directory of the driver that 
performs a frequency scan and produces a dvbrc file.  It seems to work quite 
well, but doesn't seem to parse all the service information (e.g. the list of 
other transponders).

Regards,

Dave.


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