Date: Fri, 25 Jun 1999 19:00:08 -0400 From: Randall Hopper <aa8vb@ipass.net> To: Frode Vatvedt Fjeld <frodef@acm.org> Cc: freebsd-multimedia@FreeBSD.ORG Subject: Re: bt848 channel frequencies Message-ID: <19990625190008.A2443@ipass.net> In-Reply-To: <2hpv2kba67.fsf@dslab7.cs.uit.no>; from Frode Vatvedt Fjeld on Fri, Jun 25, 1999 at 04:57:04PM %2B0200 References: <Frode <2hzp2tfr3t.fsf@dslab7.cs.uit.no> <374AA5BB.7C87D8C2@cs.strath.ac.uk> <2hogj9f0p6.fsf@dslab7.cs.uit.no> <3.0.6.32.19990626090820.007ad510@alicia.nttmcl.com> <2hemj0b617.fsf@dslab7.cs.uit.no> <2hzp2tfr3t.fsf@dslab7.cs.uit.no> <374AA5BB.7C87D8C2@cs.strath.ac.uk> <2hogj9f0p6.fsf@dslab7.cs.uit.no> <2hpv2kba67.fsf@dslab7.cs.uit.no>
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Frode Vatvedt Fjeld:
|> Roger Hardiman <roger@cs.strath.ac.uk> writes:
|> > Are you volunteering to write us handy library, called libtv which
|> > had all the frequency tables, and to modify fxtv too?
|
| * provide list of available frequency-sets [loosely related to
| country, cable/antenna etc, like "norway/cable/telenor". I guess
| some naming scheme should be worked out.]
|
| * given a frequency-set, provide list of canonical frequency-names
| [like "S21", "E7", "E8" etc.]
|
| * given frequency-set and canonical freq-name, provide frequency [in
| Hz].
|
| * given freq-set, provide list of programs/channels (what is the
| better term?) [like "BBC", "NBC" etc.]
|
| * given freq-set and program, provide frequency in Hz or canonical
| freq-name.
|
| * inverse of the above.
^^^^^^^^^^^
yes definitely, so we can infer which station we're on from driver freq
Sounds like a good first cut. Adding to what you've mentioned, see how
this grabs you:
1) Once we have libtv, we quit passing channel numbers to the driver.
We only pass it frequencies (that's the whole point I believe :-).
2) libtv (as you've said) would map between string frequency "names"
(e.g. N21,E1,10,11, etc.) and frequencies, given a frequency set.
These frequency names, and their mappings to frequencies, I'm
assuming would be universal across the entire region using the
frequency set.
3) In some cases, the user will want to create their own names for
stations (that are different than the string frequency names used
across the frequency set region) to define their local stations.
For example, in the US libtv will likely export frequency names
which are channel numbers ("10","11", "12", etc.) which locally may
be NBC, WB, CNN, etc. but are mapped different elsewhere in the
region serviced by the frequency set.
4) So it seems to me there are 2 levels of mapping that libtv needs to
handle:
StationName -to- Frequency Name (configurable locally)
FrequencyName -to- Frequency (doesn't need configured)
(This is basically what's going on now with fxtv and the bt848 driver.
Only the division of labor is different. Fxtv manages the first mapping
[where frequency name is "channel number"], and the driver manages the
second. I like the idea of pulling both of these out into libtv.)
So maybe we have FreqName-to-Freq mappings in:
/usr/local/share/tuner-freq-sets.rc
and we have StationName-to-FreqName mappings in:
/etc/tuner.rc
The advantage for getting this out of the app is of course that it can be
shared by all TV clients. Smaller, simpler TV apps and no more reinventing
that wheel :-)
For example:
/etc/tuner.rc:
NBC : 10
CNN : 55
/usr/local/share/tuner-freq-sets.rc:
10 : 144
55 : 716.69
I trivialized the syntax for simplicity. You may chose to have different
sections in the file, frequency set tag names, and other tags (whether a
freq set is for radio or TV, whether its a cable or antenna frequency set,
possibly what formats are used with it [NTSC/M, SECAM, etc.], ...).
|In addition, there must be some means to add programs etc. I expect
|there will be some global database of different countrys
|frequency-sets [like /usr/local/share/tuner-freq-sets.rc] and some
|local config-file [like /etc/tuner.rc] with default freq-sets and
|local overrides.
By the way, if this materializes in the next month, I can work out the fxtv
changes (conferences and grad school don't fire up for me until early
August, so I have some evenings and weekends free).
Let me know if I can help.
Randall
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