Teletext data on terrestrial broadcasts - sure it's on its way to obselescence, but there are useful information services hiding in there right now, and it would take, what, a single 32M DIMM to cache every single page for instant access and high quality error correction? The last three TV's I bought all had RAM and CPU's onboard anyway, so why no memory upgrade slot?-- Mharr, Aug 07 2001 Teletext Information http://www.sneezes....teletext/links.htmlInformation regarding Teletext, curiously enough. [Pallex, Aug 07 2001, last modified Oct 04 2004] Teletext is intended to be a dynamic medium, constantly updated, so there seems little point in caching *all* of the several thousand pages. At what point would the TV attempt to refresh? If the issue is simply quicker access to the next, previous, or related page, this was baked some time ago in the FLOF ('full level one features') implementation of teletext, principally offered on Nokia TVs.-- angel, Aug 07 2001 Intended as a dynamic medium, maybe, but it really isn't. Mharr really does have a point - by now, caching everything (and updating it once it changes, duh!) has become fairly cheap and should be done as a matter of routine; the whole FLOF complexity isn't needed anymore.-- jutta, Aug 07 2001 I`m sure some teletext tvs have some sort of memory,as i`ve pressed the up/down page button and its been there waiting for me.
One idea which i`m still not sure why its not used, is to put the index to the news at, say, page 102, and have the news pages at 160 to 180 (or whatever). then you have some time to choose the page. Currently the news pages (on BBC1/2) are at 102-120, so you have to wait for the whole lot to cycle around before you get the info.
Mharrs caching problems are all solvable! It could download the pages each time, compare them to the cached ones; if they differ, update the cache with the new one. Not the hardest problem in the world! (It would have to cope with multi page pages though..where you get 1/12 in the corner)-- Pallex, Aug 07 2001 It all comes down to "Bill of Materials" cost. There are entire departments at manufacturers trying to loose one or two resistors to save costs. RAM (and ROM) are hugely expensive in this context. Adding hardware complexity also means possibly more warrenty claims.
Consumer devices have very short shelf life, so it's a case of punt out the minimal functionality that will get the job done in the shortest time for the least cost.
Another issue is software quality. More complex software (caching) means more development and maintainence costs, possibly even a hugely expensive product recall. You do NOT want to see quality the software in consumer devices.
It is, however, a great idea.-- danilo, Aug 07 2001 Teletext works slightly better on your PC (if you have a TV tuner card). The text for a particular page number is downloaded and then you can flip about amongst the sub-pages to your hearts desire. Changing pages is almost instantaneous though it can take a while for sub-pages to be loaded. Obviously what goes on is exactly as Mharr describes so if it can be baked on your PC there's really no excuse for it not to be a standard feature of your TV. Croissant.-- DrBob, Aug 07 2001 I'm with [Mharr] it's simple and easy. Croissant.
The simplest method of implementation (which would probably be a compromise to [Mharr]'s vision) would be to cache every page as found using the following rules: If the channel is changed the cache is emptied. Every page broadcast is placed in the cache. If a page is already in the cache then it is overwritten when rebroadcast.
This would provide a simple system wich would requite only a 1MB cache (1000 pages at 1KB each).
As this is a *really* simple solution it would not meet the needs of : Multi-channel caching. Caching cycling groups of pages with the same page number. Error correction
[angel]: is what I've stated Nokia's FLOF or is it something different?-- st3f, Aug 07 2001 [st3f]: That's pretty much the fundamentals of FLOF as I remember it, although I've been out of that industry for some time and my personal fact-cache is failing. Multi-channel page-caching would be a problem; I don't see how you could access a page transmitted on a channel which is not selected in your tuner, unless you use a tuner which permits Picture-in-Picture (also a Nokia favourite), which I've not seen recently. Are P-i-P sets still available? <aside>That feature would also be useful for [gravelpit]'s multi-channel TV show .</aside>-- angel, Aug 07 2001 Toshiba, Sony and others already have a caching facility on some TV's that stores 500+ pages of teletext. This is baked.-- hvermin, Jan 21 2002 How do teletext and captions (if they exist) work for places that use Han characters?-- juuitchan3, Jun 15 2002 random, halfbakery