Date   : Wed, 02 Jul 2008 21:55:17 +0100
From   : info@... (Sprow)
Subject: Weird places that BBC micros could be found

In article <d8834d20807021303k2d6b0b08g6df3bc63b93b6ed4@...>,
   Alex Taylor <zeem.uk@...> wrote:
> 2008/7/2 Rob <robert@...>:

> > Thinking about it. I think lots of set computer graphics in Blake's 7
> > looked suspiciously Beeb-like, too..
>
> The main point is that the
> Amiga's got a 50Hz screen output, so it wouldn't flicker on the TV
> cameras. 

That doesn't guarantee it wont flicker: 

The 50Hz is generated by the beeb from a crystal, and the monitor will
usually have a slow loop which locks to this (the same loop the vertical
hold knob is working).

The TV camera will also have its own timing, but this isn't necessarily in
phase with the beeb - this would appear as a horizontal line on camera with
the top half and bottom half flickering (though turning off interlacing
would help).

Even if you're lucky and they start synchronised it's likely they'll roll as
one might be at 49.99999Hz the other at 50.00001Hz.

I'd gamble that the beeb and Amiga's popularity with TV folks was more the
readily available genlock solutions so that dozen's of computer's video
circuitry (and hence monitors) can be sync'd from the same reference that
the cameras are using,
Sprow.