[linux-dvb] Re: Using the tuner-simple code with digital TV decoders.

Mac Michaels wmichaels1 at earthlink.net
Thu Aug 11 07:20:00 CEST 2005


Mauro,

I use dvb-pll now. It works except for the two problems 
listed below. I see no need to change the dvb-pll code. 

Cards that share the same tuner between analog and digital 
using two different drivers have the two problems listed 
below. Using the same driver for both analog and digital 
eliminates the problems listed below. I propose adding an 
additional pll_set callback for use by cards that share the 
same tuner between digital and analog TV. Only cards that 
share the same tuner between analog and digital signals can 
use this new callback instead adding tuner data to the 
current code in dvb_pll.

With my proposal once the analog tuner is defined, the 
digital tuner is also working. This can only be used by 
cards that share the same tuner between digital and analog 
signals.

-- Mac

On Wednesday 10 August 2005 10:28 pm, Mauro Carvalho Chehab 
wrote:
> Mac,
>
> 	Patrick is working on this stuff. dvb-pll does the same
> stuff as tuner-simple, but with a different way. Maybe
> you can contact him.
>
> Mauro.
>
> Em Qua, 2005-08-10 às 22:18 -0500, Mac Michaels escreveu:
> > I have experimental code that allows me to use the
> > analog TV tuner code to support cards that use the same
> > simple 3 band tuner for both analog and digital TV
> > signals. It looks like this:
> >
> > /* The same simple tuner is used for analog and digital
> > signals */
> > struct v4l2_frequency freq = {
> > 	.tuner = core->tuner_type,
> > 	.type = V4L2_TUNER_DIGITAL_TV,
> > 	.frequency = params->frequency / 62500,
> > 	.reserved = {0,0,0,0,0,0,0,0}
> > };
> >
> > cx88_call_i2c_clients(core, VIDIOC_S_FREQUENCY, &freq);
> >
> > With a couple of tweaks to the tuner code it works.
> >
> > There are reasons that I think this code reuse is a
> > good idea:
> >
> > 1) Keeping track of the actual tuner's current
> > frequency setting. By using a single driver only one
> > copy of the current frequency is kept. Right now both
> > analog and digital drivers each keep their own copy of
> > the current frequency. This prevents optimization of
> > tuning since one tuner can change the frequency and the
> > other tuner does not know about it.
> >
> > 2) Eliminates duplication of code and tuner parameters.
> >
> > Obviously this technique will only work on tuners that
> > have minimal differences between the setting for analog
> > and digital. It would not be used on cards that use
> > different tuners for analog and digital signals.
> >
> > -- Mac
> >
> > --
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> >t
>
> Cheers,
> Mauro.




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