Date: Sun, 29 Jun 1997 16:16:06 +0100 (BST) From: Andrew Gordon <arg@arg1.demon.co.uk> To: Randall Hopper <rhh@ct.picker.com> Cc: Guido van Rooij <guido@gvr.win.tue.nl>, Steve Passe <smp@csn.net>, multimedia@freebsd.org Subject: Re: European Channel Tuning (was Re: fxtv patches) Message-ID: <Pine.BSF.3.91.970629154521.9137A-100000@server.arg.sj.co.uk> In-Reply-To: <19970628124444.04368@ct.picker.com>
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> |The reason that I want something like that is that in Europe we > |do not have channel numbers as identifiers but channel names. > |Hmm..now that I think of it: I would rather see a nnew file, lets say > |.fxtv-channels, in stead of resources. Anyway, I'd like to know > |what you plan to do with fxtv and if my views fit in there ;-) > > Well, from what you said, it sure sounds like there's a need for > frequency-to-string mappings as opposed to frequency-to-channelnum > mappings. Glancing down in brooktree848.c and searching down for "Western > European", I assume something like the names on the rightmost column of the > commented-out table are what you're talking about. > > Let me ask a few more questions to get a handle on the specifics so we can > determine the best place for this table. > > If I understood, there are no "channel numbers" in Europe, just channel > names. So I assume the channel numbers in the driver are pretty well > arbitrary. > > Also, can we assume that the channel names in a frequency-to-name mapping > table are constant for a particular broadcast standard? (e.g. a specific > frequency is always identified as "N21" or "E1"). No - certainly not at all in the UK (where I live), AFIK similar but not entirely the same elsewhere in Europe. The key point is that we have overlapping coverage areas, and so channel numbers and channel names are independent, with a mapping of one onto the other. Channel numbers map directly to frequency and are already done perfectly correctly by fxtv and the driver. Unfortunately, over here channel numbers are only used by frequency planners and technicians and the average user wouldn't have a clue what channel number he is watching. We currently have 5 channels, named "BBC1", "BBC2", "ITV", "Channel4" and "5". All TVs have a number of buttons for channel selection, each of which can be tuned to any channel number. If you have a very old TV, it will have 4 or more buttons each associated with a mechanical knob (on the back or under a flap somewhere) that allows it to be tuned in an analog manner across the entire band. More modern TVs do this with increasing degrees of automation, but still have the user interface of a number of buttons each of which can be programmed to any of the frequencies in the band, and everybody adjusts them on installation such that button 1 is BBC1, button 2 is BBC2 etc. My latest TV purchase allows you to just press a single button for auto-tune: it scans the entire band to discover which channel numbers have a signal strong enough to be worth bothering with, then decodes the teletext data from each of the active channels to extract the name, sorts them into the right order, and saves the results in EEPROM. In my area the mappings are as follows: BBC1 - 31 BBC2 - 27 ITV - 24 CH4 - 21 CH5 - 35 but 50 miles down the road it will be different. I didn't even know what channel numbers I was watching until I started using Fxtv, despite the fact that I used to work on Teletext receivers some years ago - our tuners had analogue adjustment back then, so knowing the channel number wasn't useful. Cable is more like the US system, with large numbers of arbitrary channel numbers mapped onto content by the cable system operator (though most will map the five broadcast channels onto the first 5 cable channels). This however is not particularly interesting to Fxtv, since the cable set-top-box is supplied by the cable operator and the user is not normally allowed to connect direct to the cable (the STB handles scrambling etc. to ensure that you can only see channels you have paid for).
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