gnupic: Thread: Re: pic pong with gpsim

On Fri, Mar 14, 2003 at 12:59:01PM -0400, Daniel Serpell wrote:
> 
> On Thu, Mar 13, 2003 at 08:06:11PM +0100, Ralf Forsberg wrote:
> > 
> > However, I'm having problems differentiating between the vertical sync
> > pulses for field0 and 1. Need that to get the interlazing layers on the
> > right place.
> 
> Count the number of equalization pulses (eq. pulses are at
> twice the H freq) after VB.
> ->Even number of pulses -> even frame
> ->Odd number of pulses -> odd frame.

I do almost exactly that now, only I compare the number of pulses with
the number in the last frameand guess that the one with more pulses
is 'first' frame. Is that the same thing, or would it be better to
compare odd/even?

> 
> This will work for NTSC too.

I tried my version on the ntsc pong game and that worked too.
It's now also in cvs.

 / Ralf

On Thu, Mar 13, 2003 at 08:06:11PM +0100, Ralf Forsberg wrote:
> 
> However, I'm having problems differentiating between the vertical sync
> pulses for field0 and 1. Need that to get the interlazing layers on the
> right place.

Count the number of equalization pulses (eq. pulses are at
twice the H freq) after VB.
->Even number of pulses -> even frame
->Odd number of pulses -> odd frame.

This will work for NTSC too.

    Daniel.

On Thu, 13 Mar 2003, Ralf Forsberg wrote:

> 
> I started coding a PAL-video module for gpsim. It uses two inputs to
> control four levels. Not coincidentally like in pic-pong.
> http://www.efd.lth.se/~e96rg/mc/video/pong.html
> 
> Here is a pic-png :-) of the title screen simulated with gpsim:
> http://www.acc.umu.se/~rfg/pong.png

This is impressive!

Scott

On Fri, Mar 14, 2003 at 06:28:36PM +0100, Ralf Forsberg wrote:
> On Fri, Mar 14, 2003 at 12:59:01PM -0400, Daniel Serpell wrote:
> > 
> > Count the number of equalization pulses (eq. pulses are at
> > twice the H freq) after VB.
> > ->Even number of pulses -> even frame
> > ->Odd number of pulses -> odd frame.
> 
> I do almost exactly that now, only I compare the number of pulses with
> the number in the last frameand guess that the one with more pulses
> is 'first' frame. Is that the same thing, or would it be better to
> compare odd/even?
> 

Yes, should work in "correct" TV signals, because the number of
equalization pulses should be the same in all even or odd frames. The
difference will be in "bad interlaced" signals: if the difference in
pulses is betwen frames is even, a TV set will display the two fields
in the same possition, in fact the number of eq. pulses set's the
vertical position in the frame (each eq. pulse ammounts to half a line,
that's why you show even/odd fielfs interlaced).

Some TV output circuits (like the one in my old Atari 800) output
non-interlaced signals, in this case the two fields have the same number
of eq. pulses.

    Daniel.