Re: Convert 15KHz to 30KHz?

[Hans Otten <nobody@yahoo.com>]

"Bryan Parkoff" <bryan.nospam.parkoff@nospam.com> wrote:

>    I have seen that someone tried to convert 15KHz horizontial sync to
>30KHz horizontial sync from Apple IIgs' RGB to VGA monitor.  The trick is to
>add blanking sync.  First line is displayed, second line is blanking, third
>line is displayed, four line is blanking, and so forth until it reaches 400
>lines.  It is like that displaying is odd and blanking is even.
>    The convertor device receives 15KHz from Apple IIgs' RGB before it adds
>another 15KHz as blanking.  It equals to 30KHz before it starts to display
>on VGA monitor.  I am sure that mixing odd and even lines do not look good.
>Someone did try to duplicate odd lines into even lines that is called double
>line per single line.  It may be a clever trick, but it is very rare that no
>one is doing a test yet.
>    Did you test to work with LCD that supports 15KHz?

There are (not cheap) devices with a technology called scan doubler that display
rgb (interlaced) 15 KHz signals  fine on a VGA monitor as (de-interlaced) 30 KHz
signals. 

Hans, http://www.hansotten.com