[linux-dvb] DVB-S2 Multiple logical TS on the same frequency

Francesco Schiavarelli kaboom at tiscalinet.it
Fri Oct 19 22:09:30 CEST 2007


Manu Abraham wrote:
> Francesco Schiavarelli wrote:
>> Manu Abraham wrote:
>>> I guess it uses FEC short Frames and a Rolloff of 20%.
>>> Currently we use FEC normal frames and a Rolloff of 35%. I will check
>>> on this though.
>> Do you mean Rolloff and FEC type are somehow hardcoded in current
>> linuxtv STB0899 driver?
> 
> Currently with CCM, we never had to worry about FEC long or short frames 
> as it is always normal (LONG) frames with regards to CCM.
> 
> The STB0899 driver doesn't take rolloff as a parameter from either from 
> the user in the form of the S2 delivery system descriptor, or from a config 
> file.
> 
> It is in fact extracted from the Baseband header and used, thereby leading 
> to "no" assumptions, in some cases the the SI can be wrong or missing, but 
> the BaseBand header, not. So the STB0899 relies on a reliable method of 
> extracting the rolloff and hence thereby the bandwidth of the same.

Thanks for the clarification.

>> If needed I can ask and provide here more detailed transmission
>> parameters regarding this transponder...
> 
> This would be great, much appreciated.
>  
>>> It looks like a DSNG profile, some uplinks as far as i can guess.
>> I can confirm that this feed will be used by local terrestrial DVB-T
>> transmitters, if I understand correctly your guessing.
> 
> Yes, that is what i understand too. This profile uses ACM, well i need more 
> inputs to have this implemented (ie this is currently an unimplemented 
> feature, although it can be implemented)

I don't think so. The signal I'm interested should use CCM, when asking 
for more details I was pointed to EN 302 307 annex H.2
Also ACM needs a return channel and I know for sure that in this case is 
not used.

Anyway ATM the feed is gone, but it should be up again next week with 
some minor modification, when it's ready I'll keep you informed.

Francesco



More information about the linux-dvb mailing list