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Dr John Hawkins

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More Adventures in the Land of VBI

Posted on 2006/08/22 01:03:57 (August 2006).

[Thursday 17th August]
Stayed really late at the office - until about 10PM.

A lot of this time was spent waiting around for my PC to finish long jobs. So I spent the time constructively trying to decipher ARIB STD-B5.

This is the standard for Japanese VBI based data transmission - their version of Teletext and subtitles on analogue TV. It was really tough - the PDF appears to have been scanned in, so there was no option to just copy and paste into Google translate or whatever. It's not even easy to retype Japanese text like you could with English - I either have to know how to pronounce each Japanese character to type it, or alternatively I can try a few lookup mechanisms based on radicals or numbers of strokes or even a primitive thing that lets you draw the kanji and tries to recognise it... but the dictionary runs into many thousands, so it is no mean feat!

Plus the bit that I'm currently trying to work on - the actual modulation of the VBI signal - is really quite different to anything I've done before. Usually I start with a clean signal of 1s and 0s and go from there. With VBI though the data is modulated into a signal in the image data - so I've got to demodulate that first (in software) before I can make any sense of it. Take a look at a tool called VBI Scope (which incidentally I've found very useful) to get an idea of the task in hand. Actually having said that, the VBI data shown there is a really clean signal (possibly NTSC closed captions?) - part of the reasonm I'm really struggling is that the signals I've been getting from both the tuners I've tried have been really, really noisy.

So I'm working in a technical area I don't really understand based on a spec written in a language I can hardly read. I think I may have bitten off more than I can chew here!



Comment 1

Got to hand it to you John, that is *really* stacking the odds against you!! Well done for attempting the task so pragmatically!

Posted by Nigel at 2006/08/22 09:40:08.

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