[linux-dvb] [PATCH] frontend.h add dvb-s2 support including backwards compability

Marcel Siegert mws at linuxtv.org
Thu Feb 23 09:55:57 CET 2006

hi patrick,

On Wednesday 22 February 2006 21:39, Patrick Boettcher wrote:
> I am not a signal expert, not at all, but wouldn't it be better to rename 
> QPSK_8 to 8PSK and QPSK_B to BPSK? (and accordingly FE_CAN_..)
> (see http://en.wikipedia.org/wiki/8PSK)

imho it is not allowed by c/c++ naming conventions to start a var with a 
number instead of a char. 

we do only have _one_ enumeration value left. that's why i thought to use that as
a flag for signalling for the newer types (eg. dvb-s2) that there is more information
in backported api v4 stuff like
	enum dvb_fe_code_rate  caps_fec;        /*!< supported fecs */
	enum dvb_fe_modulation caps_modulation; /*!< supported modulations */
	enum dvb_fe_common_cap caps_common;     /*!< supported common capabilities */
	enum dvb_fe_other_cap  caps_other;      /*!< supported other capabilities*/

have a look within the api v4 repository within frontend.h

> http://en.wikipedia.org/wiki/DVB-S2 also mentions higher PSK-modulations.
ETSI Standard 300468 has reserved 2 bits to define modulation.
AUTO, QPSK, 8PSK & 16-Quam ( which is marked as not available for dvb-s2 )

> As this is a good chance we might also consider adding the additional 
> DVB-H parameter (taking the additional TPS-values into account)?
i do not know anything in detail from dvb-h until now.
but of course, if there are details available already we should integrate it within
another patch. _BUT_ see above for the enumeration (CAN... ) problem we do 
actually have.
> What about the problems discussed last week about the hierarchy-parameter 
> and the selection of LP and HP streams (+ ALPHA value) for DVB-T/H?
i didn't follow that discussion, will try to read up.

> IIRC, during the discussion in November someone also mentioned, that 
> DVB-S2 also support hierarchical transmissions...
yes, ETSI TR 102 376 v1.0.1 page 26 gives us more information about that topic.
backwards compatibility for dvb-s:
a) LP/HP constellation is to perform layered modulation 
    (not available - would cause new satellites to be launched)
b) having DVB-S/DVB-S2 mixed up within a 8PSK modulation, this is an option,
    but i actually do not know a dvb-s2 frontend is implemented to have dvb-s2 
    modulations, but output would be dvb-s data (means how to select the HP stream)

maybe some other people on the list have more specific knowledge? 


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