[linux-dvb] DVB-S2 / Multiproto and future modulation support

Steven Toth stoth at linuxtv.org
Wed Sep 10 20:47:03 CEST 2008

Hans Werner wrote:
> -------- Original-Nachricht --------
>> Datum: Wed, 10 Sep 2008 17:10:19 +0200
>> Von: Christophe Thommeret <hftom at free.fr>
>> An: Steven Toth <stoth at hauppauge.com>
>> CC: linux-dvb at linuxtv.org
>> Betreff: Re: [linux-dvb] DVB-S2 / Multiproto and future modulation support
>> Le Wednesday 10 September 2008 15:38:23 Steven Toth, vous avez écrit :
>>>> Is this card able to deliver both S and T at the same time?
>>> No, the hardware can do S/S2 or T.
>>> The driver in the S2API tree only has S/S2 enabled (for the time being).
>> So, maybe we have to think a bit about how to add support for this kind of
>> device.
> Yes, absolutely, and I hope this can go in to S2API and the kernel. It would be a lie
> to claim that linux supports the HVR4000 until this is done. Fortunately Steven
> and Darron made experimental drivers which do this.
>> I mean, if the driver provides different adapters/frontends (say 
>> adapter0/frontend0 and adapter1/frontend0), a typical application will see
>> these as separate devices, and then when a user watch a S channel, the app
>> assumes that the T frontend is free while in fact it's not.
>> For example, Kaffeine updates its channels list according to which
>> channels 
>> can be viewed (based on which frontends are free). So, if you are
>> recording a 
>> S channel, all channels on this freq are shown as available and all T 
>> channels are also shown as available. But in the HVR4000 case, it's false,
>> since the T tuner isn't free.
>> Maybe a solution could be to have :
>> - adapter0/frontend0 -> S/S2 tuner
>> - adapter0/frontend1 -> T tuner
> This is what the multifrontend (mfe) driver at http://dev.kewl.org/hauppauge does.
> And Kaffeine is the only major DVB app which correctly finds the two frontends
> and uses them correctly (well done!!). Or very nearly -- TV watching is perfect, but
> the only slight problem happens when you are recording:
> (1) record a DVB-T channel:
> -->all DVB-T channels except those in same multiplex vanish from the available
> channels list (correct)
> -->no satellite channels vanish (incorrect)
> (2) record a DVB-S channel;
> -->all DVB-S channels except those on the same multiplex vanish from the available
> channels list (correct)
> -->no DVB-T channels vanish (incorrect)
> It's a small problem, easily fixed I would think.
>> So applications could know that these 2 frontends are exclusive.
>> That would not require any API change, but would have to be a rule
>> followed by 
>> all drivers.
> Yes, if we keep to that rule then only frontends which can operate truly
> simultaneously should have a different adapter number.

If everyone wants this in the S2API tree then it's pretty simple to add, 
I just didn't want to overload the tree with too much baggage that 
causes it to get stuck in the approval process.

We need an S2 API in the next few weeks, and anything that delays that 
is bad news for everyone.

I'll publish a mail about this in a separate thread, and seek feedback 
from everyone.

- Steve

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