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

Manu Abraham abraham.manu at gmail.com
Fri Nov 2 22:47:25 CET 2007


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

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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