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

Darron Broad darron at kewl.org
Tue Oct 14 19:02:03 CEST 2008

In message <200810141451.02941.hftom at free.fr>, Christophe Thommeret wrote:


>Le Tuesday 14 October 2008 12:29:49 Darron Broad, vous avez =E9crit=A0:
>> 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 file=
>> 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=20
>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.=

It doesn't include modulation because QPSK is implied.

>Maybe there is not a single 16QAM TP all over the world, but it's still a=20
>valid modulation for DVB-S.

As is said, the cx24116 only does PSK.

The driver should return unsupported for anything it can't do.

If someone out there actually uses 16-QAM (who are you?) and that person
switches to an adapter with a cx24116 they should be informed of error
when tuning 16-QAM, not acceptance of something it doesn't support.

>So, we set modulation to QAM_AUTO when it's unknown/unspecified, like in=20
>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=20
>instead of returning a notsup.
>See this as software QAM_AUTO :)

>This is with s2api.

When you use DVB-S delivery you should set the modulation to QPSK. If
an end-user out there really needs 16-QAM then you should allow them
the option to change it to QAM_16. I do not think this is going
inconvenience many people.



 // /
{:)==={ Darron Broad <darron at kewl.org>
 \\ \ 

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