[linux-dvb] Multiple frontends on a single adapter support

Christophe Thommeret hftom at free.fr
Thu Sep 11 15:35:19 CEST 2008


Hi all,

( Please don't mix this thread with the "DVB-S2 / Multiproto and future 
modulation support" thread. )

Summary:

Some devices provide several tuners, even of different types.
So called "Dual" or "Twin" tuners can be used at the same time.
Some others (like HVR4000) can't be used at the same time.

My initial question was: How could an application know that 2 (or more) tuners 
are exclusive (when one is used the other(s) is(are) not free.)

I suggested the following:
Since actually all multiple tuners drivers expose several fontend0 in separate 
adapters, maybe a solution for exclusive tuners could be to have :
- adapter0/frontend0 -> S/S2 tuner
- adapter0/frontend1 -> T tuner
so, an application could assume that these tuners are exclusive.

Janne Grunau acked the idea and said that an experimental driver for HVR4000 
is already doing this.

This was confirmed by Steven Toth:
"Correct, frontend1, demux1, dvr1 etc. All on the same adapter. The 
driver and multi-frontend patches manage exclusive access to the single 
internal resource."
	
Andreas Oberritter said:
"This way is used on dual and quad tuner Dreambox models." (non exclusive 
tuners).
"How about dropping demux1 and dvr1 for this adapter (exclusive tuners), since 
they don't create any benefit? IMHO the number of demux devices should always 
equal the number of simultaneously usable transport stream inputs."

Uri Shkolnik said:
"Some of the hardware devices which using our chipset have two tuners per 
instance, and should expose 1-2 tuners with 0-2 demux (TS), since not all DTV 
standard are TS based, and when they are (TS based), it depends when you are 
using two given tuners together (diversity  mode, same content) or each one 
is used separately (different frequency and modulation, different content, 
etc.)."



So, here are my questions:

@Steven Toth:
What do you think of Andreas' suggestion? Do you think it could be done that 
way for HVR4000 (and 3000?) ?

@Uri Shkolnik:
Do you mean that non-TS based standards don't make use of multiplexing at all?


-- 
Christophe Thommeret




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