[Coco] PopStar Pilot - Another chapter added

[Arthur Flexser]

I seem to recall, and maybe this is what you're saying, that indeed
each frame consists of half blank lines, and the next field duplicates
the first except that each line is shifted one line downward (or
upward).  Not true interlace, on account of the even lines duplicating
the odd rather than being an independent scan.  That's what I remember
that the spec sheets for the VDG said, or how I interpreted them,
anyway.

Art

On Sun, Oct 6, 2013 at 11:06 AM, Richard Goedeken
<Richard at fascinationsoftware.com> wrote:
> I've looked at this with a scope.  I forget the exact details, but there is
> a pulse train at the beginning of an NTSC frame, and something about this
> pulse train tells the TV whether the coming field is an even field or an odd
> field.  The way that the Coco (and nearly all the old computers and game
> consoles) generate the NTSC signal, is that they always give the same field
> type (even or odd).  So the signal is like 60-hz progressive, but half of
> the lines are always dark.  In order to get true interlace, you need to set
> up the video generator to correctly generate this sync signal so that the TV
> will see alternating even and odd fields.  I don't know if the VDG/GIME is
> capable of this.
>
> Richard
>
> On 10/06/2013 12:42 AM, Nick Marentes wrote:
>>
>>  > I've not looked closely at the GIME, but it's probably just like the
>>  > VDG: instead of 525 line ~30Hz interlaced, it generates 262 line ~60Hz
>>  > progressive. No half lines, etc..
>>
>> I don't know if it's progressive. I thought all "old-school" monitors such
>> as
>> the CM-8 were interlaced. Progressive was part of VGA monitors.
>>
>> Correct me if I'm wrong. Anyone shed some light on this?
>>
>> Is the CoCo producing 30 frames per second interlaced (30 blank fields
>> interlaced with active fields) or is it actually producing 60 frames
>> progressive?
>>
>> Nick
>>
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