[linux-dvb] DVB-S2 API vs. HVR4000: When?

Manu Abraham abraham.manu at gmail.com
Fri Nov 2 23:01:39 CET 2007


Manu Abraham wrote:
> Hi Johannes,
> 
> Johannes Stezenbach wrote:
>> On Sat, Nov 03, 2007, Manu Abraham wrote:
>>> When Johannes stated: handling multiple streams is as simple as setting 
>>> a stream id, well it is not that i blame him, the specs look that way. There 
>>> are couple of ways the same thing is done for example. You apply a 
>>> wrong one and the API is screwed and you have to bear that brunt for 
>>> a long time to come.
>> Hey, if you know more than I do then please explain it to me.
>>
>> Until proven wrong I continue to believe that there isn't any more
>> magic to handling multi stream mode than choosing one of them
>> by writing the stream id into the appropriate demod register.
> 
> ;-) of course. I have learned it the hard way, that proving a person 
> wrong can be disastrous.
> 
> Nevertheless i will explain my understanding, eventhough not a 
> great one. :)
> 
> If you see H.2 and H.3, the difference is between CCM and VCM
> (Note: that both are cases of multiple "TS's")
> 
> H.2 (CCM) is applicable for DVB-T muxes. Here there is a HP/LP 
> stream selection in some fashion combined with the merger/slicer 
> where stream id is used. 
> 
> It is a combination of both, rather than a simple stream id.
> (In this case Rolloff=0.20, Pilots do not exist) in this case the 
> QPSK stream is with FEC 5/6 
> 
> H.3 (VCM) is applicable for a HDTV/SDTV mux. here it is quite similar 
> to H.2 exception that (In this case Rolloff=0.25, Pilots do exist)
> in this case the QPSK stream is with FEC 3/4 and the 16APSK stream 
> is with FEC 3/4
> 

Also, i forgot to mention one more thing, 16APSK is denoted as 
4 + 12 APSK, (for the demod) not sure why either.

> H.2 is playing with the DVB-S signal level (saturating a transponder) 
> where as H.3 is using differential protection. It is not very clear how 
> both of these are distinguished from each other.
> 
> Also, on the demod other than the MIS flag (according to the specs) 
> there is another bitfield to select the HP/LP stream, which makes it a 
> bit even more confusing. There exists some clarity, but again there are 
> some clouds which hinder how it looks.
> 
> I am not really very clear on handling this. We will get more clarifications 
> the coming days.
> 
> Manu
> 




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