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

Manu Abraham abraham.manu at gmail.com
Fri Oct 19 22:42:28 CEST 2007


Francesco Schiavarelli wrote:
> 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.
> 

Ahh. I meant to write VCM, not ACM according to TR 102 376
Section: 5.2

In this case can you check whether the transmission is Hierarchial BC 
(Backward Compatible) or Layered BC ?
Section 4.4. Layered BC mode doesn't exist on old satellites, but ..

The reason being, why i am doubtful: if you used the STB0899, with Hierarchial BC 
mode you should have seen at least the HP stream. (scratching head)

> 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.

I don't have access to that satellite, if you have a STB0899 based, you can try it, but 
before that you need to verify your setup works fine.

Manu



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