[linux-dvb] Re: Hello

[Holger Waechtler <holger@convergence.de>]

Brian Korsedal wrote:
>  >The Philips tda10045 and the nxt6000 can receive both UHF and VHF. And
>  >they are a bit more sensitive.
>
> cost isn't much of an issue, so we will probably go with one of these 
> cards.
These cards are even cheaper as the fullfeatured card with the Grundig 
tuner...


>  >Note that you need en external (hardware or software) MPEG decoder
>  >unless you use the fullfeatured card.
>
> We plan on using the device as a video server running VideoLan server 
> (www.videolan.org)
Well, then the cheap Nova cards are your favorites.


>  >The stepsize is usually 62500, 166667 or 250000kHz, refer to the source
>  >for details. But why should you want to know this, after all you should
>  >be able to tune to the continous frequency spectrum if the driver is
>  >properly coded, right? The AFC is doing the rest...
>
> The step size is determined by a lot of factors.  It is more hardware 
> dependant that software dependant.  It has to do with PLL's and 
> filters.  I hope you meant 250000 Hz instead of kHz.
oops, yes -- you are right. Basically all PLLs provide a free choice 
over a number of stepsizes within the range 62.5kHz...500kHz, sometimes 
even more.

>  If we can get a 
> card that can tune with a step size of 62,500 Hz, that would be 
> amazing.  It would be cheaper and perform better than our current 
> product.  By cheaper, I mean a lot cheaper.  We do all custom 
> electronics for our devices and they cost at least $10,000 to produce.
As mentioned in my first mail, the actual PLL stepsize has nothing to do 
with the quality of the entire tuner module. If you program your PLL 
with a big stepsize you can still preset your AFC to achieve fast locking.

And the AFC can always balance out frequency offsets wider than a 
stepsize...

> Would Debian or Suse be good distributions for this project?  If I have 
> to get the plain kernel, what packages do I need to get to make this 
> work?  I do not need X windows.  I just need to get the video in, tune 
> the card and use video lan to broadcast the stream.  A virtual private 
> network would be nice.  I think this can be done with ssh.
Choosing a distribution is always a matter of personal preferences, in 
your case it even may make sense to build your own simple distribution 
containing only the kernel, a simple init system (maybe only a bash 
script - ), ssh and the DVB tools (the latter you want to build on your 
own anyway...)

Holger



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