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From: Steve Passe <smp@csn.net>
To: Richard Tobin <richard@cogsci.ed.ac.uk>
cc: multimedia@freebsd.org
Subject: Re: Changes for Audio control on the bt848 code 
In-reply-to: Your message of "Sat, 22 Mar 1997 17:58:06 GMT."
             <24447.199703221758@pitcairn.cogsci.ed.ac.uk> 
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Date: Sat, 22 Mar 1997 11:53:46 -0700
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Hi,

> > Note that this driver changed the string TUNERTYPE_xxx to CHNLSET_xxx,
> 
> That reminds me, why is the mapping of channels to frequencies done in
> the kernel?  It seems excessive to have to rebuild the kernel to add
> frequencies for other countries.

There is an ioctl to directly plug in frequencies if you want,
but I don't believe that an app should have to be aware of the math necessary
to create the IF frequency for the tuner hardware.  The total calculation
requires knowledge of the tuner model and/or card setup.  it depends on
the programmed step size (ie granularity) used by the predivider.  it
may also vary from PAL to NTSC, I haven't investigated that yet.  there
is also the issue of advanced features like "channel search".  to do
this the kernel needs to know all the above fundimental data anyways,
so nothing to be saved by forcing the app to do channel math.  Remember
that an app should be able to work with different types of hardware, there
is no guarantee that all future boards of this class will user bt848 chips
or temic/philips tuners.

--
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