405 lines from Raspberry Pi 5

[ppppenguin]

Almost 20 years ago I wrote an article for the BVWS Bulletin saying that you couldn't us an ordinary PC for real-time standards conversion.

Some have suggested using computers or digital signal processors (DSP). Conceptually there is no problem. I’m a pretty lousy programmer and I could write you the conversion algorithms in a few lines of a high level language such as BASIC. These would take a 625 line image, already in the computer, and convert it to a 405 line image, also within the computer. And there’s the snag. You still need to get the picture in and out and you have to ensure that the computer can keep up with the data. Video comes at you continuously so real time means exactly that – you cannot put your hand up, take time out and catch up later. So when you say you have built a converter with a cast off 486 PC I won’t believe you.

In 2006 Kat Manton proved me wrong by showing 405 out from a PC. This used MythTV Linux. Others worked on similar methods, both in Windows and Linux. These all used the capabilities of modern graphics cards to do just about any line standard.

Now it looks possible on a R-Pi. It's not too hard to envisage a standard set of hardware and a downloadable SD card image to make a converter very simply and at low cost.

There is still a place for custom logic as in the Hedghog but advances in computing make so many things possible.

I've attached a photo of the converters that Lucien and I installed at Dulwich. The silver fronted kit is the CO6/509 digital, most of the rest is the CO6/501 analogue. Both converters are now at the Broadcast Engineering Museum. The CO6/501 would take a huge effort to restore. It won't happen. The CO6/509 would probably be got going relatively easily but it's very low priority for us.

If you come to our open days on 25/26 May they won't be on public display but if you ask, I'll take you to the stores to show them to you.