[linux-dvb] Multi Tuner Cards

Ralph Metzler rjkm at metzlerbros.de
Tue Oct 18 10:46:59 CEST 2005


Patrick Boettcher writes:
 > Hi Marco,
 > 
 > On Mon, 17 Oct 2005, Budde, Marco wrote:
 > > Let's assume I want for write a DVB module
 > > for a card containing two paths. Each path
 > > has got its own tuner, which supports for
 > > example two standards: DVB-T and DVB-S.
 > 
 > As to my knowledge with the Linux DVB API 3 (which is currently used) it's 
 > not possible to handle devices with multiple frontends (and thus multiple 
 > muxes to demux) within one (software)-DVB-Adapter.
 >
 > To achieve I think this you have to register one DVB-Adapter for each 
 > frontend/mux-stream-combination in your driver. Up to 6 DVB adapter can be 
 > created at the same time with the current implementation.

For a dual tuner card I implemented it both ways, using two adapters
or using one adapter with front0/1, demux0/1, etc.

Using two adapters has the advantage that more software works with
it. Some programs do not support front1, etc.
Using one adapter for all tuners is also no problem with API 3 if all
tuners and demuxers are independent. 

But in your case there are tuners with different standards but the
same output? (Btw., who builds such tuners?) 
You could still use 1 adapter and allocate 4 tuners, etc., you 
just should not use front 0 and 1 or front 2 and 3 at the same time ...
That might be a problem but you would have the same with 4 adapters
where only 2 could be used at the same time.

I also don't think the elsewhere mentioned SET_SOURCE call or API 4
would help much. Or is there support for multi-standard tuners or
for the case that 2 specific tuners cannot be used at the same time?
You could e.g. only allow front0/1 as source for demux0 and front2/3
for demux1 and otherwise return -EINVAL but then all the software 
out there would have to "scan" all possible combinations first. 

Ralph










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