Divergent hobbies and new projects

Hmm. I seem to have found another interest.

Video electronics. More specifically, data transmission over analogue TV (and also video generation, but that’s a sideline at the moment).

There’s been some talk on the bbc-micro mailing list about the upcoming discontinuation of ITV Teletext, and how neat it would be to have an archive of the various Teletext services at a given time, and be able to either view them on a PC (or even a BBC Micro), or inject them into an analogue video signal.

I’ve found a copy of the original “Broadcast Teletext Specification”, September 1976, by the BBC, IBA and BREMA (it’s on http://www.doc.ic.ac.uk/~ih/teaching/teletext/ if you guys want to have a look). Basically, this is the document that described the Teletext standard as it was at the start. It covers the bare essentials, and nothing more (unlike the ETSI EN 300-706 standard, which covers **everything**).

I figure I might have a go at building a Teletext receiver out of a couple of opamps, some passive components, some RAM, and an FPGA. Basically a box that takes a CVBS/FBAS composite video signal, waits for the VBI, strips the data from the Teletext packets and stores said data in RAM. A microcontroller then reads that data out of RAM and feeds it to a PC for storage.

I’ve also got two books on order from Amazon — “Basic Television and Video Systems” by Bernard Grob, and “Video Scrambling and Descrambling for Satellite and Cable TV” by Rudolf Graf. The latter is more to satisfy my slight interest in TV conditional-access systems, the former to learn more about TV transmission and reception technology.

I’ve got a box full of Philips UV916MD tuners, so I guess I just need to hack together an IF filter and demodulator, and see if I can at least get a valid (if somewhat shoddy) CVBS signal off of one of the broadcast TV channels…

One thing’s for sure, it’s going to be a fun week. Month. Year. Whatever.