Date   : Thu, 02 Jan 2014 13:22:01 +0100
From   : kortink@... (John Kortink)
Subject: Modernisations

On Thu, 2 Jan 2014 12:50:39 +0100, "Anders Carlsson"
<anders.carlsson@...> wrote:

>Paul Vernon wrote:
>
>>> I noticed John mentioned a Beeb to VGA converter
>> Yes, something like this is suitable...
>> http://www.ebay.co.uk/itm/RGB-RGBS-TO-VGA-converter-1-VGA-for-arcade-game-etc-/260847913225
>
>A few years ago I bought one of those and while it does it job, it adds a 
>little delay on the picture. For your daily word processing, programming and 
>perhaps art drawing needs it might be acceptable, but you might find that 
>some action games will be more difficult to play if you see on screen what 
>is happening 0.2 seconds after the CPU decided it already happened.

Interesting. I would not have thought it was noticable.

>YMMV, and the firmware and size of programmable chips may have improved to
>shorten the lag.

It is unlikely.

You have an interlaced source, but, in most cases, a non
interlaced target. While this conversion can be done in a
progressive way (rendering source lines to an intermediate,
and rendering the intermediate to the target at a different
frame rate), the source and target frame rates are close
enough to make this impractical and/or subject to specific
artifacts. In general, the converter will therefore render
to the target not at the line rate, but at the frame rate
of the source. Hence the lag of 0.2 seconds.

>I don't know about HDMI, but if you have a display that takes SCART RGB, it 
>is not rocket science to convert the TTL RGB signal from the Beeb to analog 
>level signals. I realize this neither what John nor Thomas was asking about, 
>and I also understand that any signal converter can't operate at the speed 
>of light, but perhaps it would be better to look for a RGB to HDMI converter 
>from the start than going through VGA as a middle step.
>
>I noticed there are a few RGB/component to HDMI converters on eBay, but I 
>don't know if they'd be suitable with a BBC Micro, with or without 
>additional circuitry. My bet is on "not compatible out of the box", but I'd 
>glad to be proven wrong.

There have been a few more 'native' efforts, but, as is
often the case, none of these are available as a finished
product. One can speculate about the cause of this.

I could do one, but many factors (including lack of time,
and the complexity of doing it well, i.e. auto-detection,
configurability, several resolutions, letterboxing, etc.)
prevent that from happening. At least anytime soon.


John Kortink