[linux-dvb] [PATCH] cx24116 DVB-S modulation fix

Christophe Thommeret hftom at free.fr
Tue Oct 14 14:51:02 CEST 2008


Le Tuesday 14 October 2008 12:29:49 Darron Broad, vous avez écrit :
> In message <200810141133.36559.hftom at free.fr>, Christophe Thommeret wrote:
>
> hi
>
> >Hi,
> >
> >This patch makes cx24116 to behave like other dvb-s frontends.
>
> Unlike most DVB-S cards the those with a cx24116 use S2API
> this makes them somewhat different.
>
> >This is needed especially because QAM_AUTO is used in a lot of scan files.
>
> What scan files are you referring to? The
> cx24116 only does PSK, not AM. QAM_AUTO
> doesn't sound right. the cx24116 can't
> auto detect anything, but that's another
> story...

dvbscan initial tuning data files for DVB-S don't have an entry for 
modulation. So an app like kaffeine simply set modulation to QAM_AUTO.
Why not QPSK, you ask? Simply because DVB-S standard allows QPSK and 16QAM. 
Maybe there is not a single 16QAM TP all over the world, but it's still a 
valid modulation for DVB-S.
So, we set modulation to QAM_AUTO when it's unknown/unspecified, like in 
dvbscan files (those being also used by kaffeine). And it works pretty well, 
just because most dvb-s can only do QPSK and so force modulation to QPSK 
instead of returning a notsup.
See this as software QAM_AUTO :)

P.S.
This is with s2api.

-- 
Christophe Thommeret




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