[Coco] French CoCo

[gene heskett]

On 12/1/22 23:42, M. David Johnson via Coco wrote:
> Hmmmm. Well, phooey!
> 
> And I don't suppose there's any way to filter the CoCo's video to make it conform to actual NTSC?

No, its broken from the gitgo. When the coco was born, tv stations were 
still using a 30 tube sync generator and it wasn't till the early 90's 
that a complete sync generator on a chip was first made. Generating 
proper NTSC signals is a mathematical nightmare. There was a Grass 
Valley Group generator solid state that wasn't too bad by 1972, but it 
had lots of 7400 family chips in it, and took up 2 rack spaces full width.

We've had several folks build an rgb driver, but that only for coco-3, 
as the earlier ones had only the rf or composite which predictably went 
ugly the instant the tv makers started using real "comb" filters.
I do not now remember the name or number of that generator chip, and I'd 
imagine by now they've all gone to the landfill.

Unfortunately, the technology has moved on and left us in the dust. For 
us, there should be an emulator that runs on modern hardware, like the 
credit card sized bananapi m5, beats the rpi4b. Specially in price.
> 
> Basically, I've got four CoCo 2's. One is running fine using CoCoVGA. But it looks like ever getting any more CoCoVGAs may simply not happen.
> 
> --
> M. David Johnson
> mdj at bds-soft.com
> 
> -----Original Message-----
> From: Coco <coco-bounces at maltedmedia.com> On Behalf Of gene heskett via Coco
> Sent: Thursday, December 1, 2022 3:05 PM
> To: coco at maltedmedia.com
> Cc: gene heskett <gheskett at shentel.net>
> Subject: Re: [Coco] French CoCo
> 
> On 12/1/22 14:33, M. David Johnson via Coco wrote:
>> On a side note, I was under the impression that the video output on the CoCo 2 is straight RF.
>>
>> I recently picked up an RF-to-HDMI converter to experiment with and,
>> of course, the lashup produces no HDMI picture ☹
>>
>> Could anybody point me towards what I'm likely to be missing here?
>>
>> --
>> M. David Johnson
>> mdj at bds-soft.com
> 
> Probably not you. That convertor probably expects to see a genuine NTSC signal from the coco and its so far off in some of the tech details that a digital convertor will likely never lock to it. The color subcarrier frequency is about right so analog color works, but nothing in its sync signal is any better than it takes to make an elderly 1950's analog tv work, ugly result but makes pictures. The digital circuitry cannot cope with the errors.
> 
> I was a tv chief engineer much of the NTSC days, retired in 2002, NTSC was last seen in the US up till midnight, June 30th, 2008.
>>
>> -----Original Message-----
>> From: Coco <coco-bounces at maltedmedia.com> On Behalf Of Allen Huffman
>> via Coco
>> Sent: Thursday, December 1, 2022 10:33 AM
>> To: CoCoList for Color Computer Enthusiasts <coco at maltedmedia.com>
>> Cc: Allen Huffman <alsplace at pobox.com>
>> Subject: Re: [Coco] French CoCo
>>
>> SCART interface for video built in? Interesting. "the only differences with other versions are the Scart video connector and the Azerty keyboard. This "feature" can cause some compatibility problems with some games..."
>>
>> I guess I missed that. So we had the traditional RF CoCo, some that had composite video (educational model) and a SCART model… any others?
>>
> 
> Cheers, Gene Heskett.
> --
> "There are four boxes to be used in defense of liberty:
>    soap, ballot, jury, and ammo. Please use in that order."
> -Ed Howdershelt (Author, 1940)
> If we desire respect for the law, we must first make the law respectable.
>    - Louis D. Brandeis
> Genes Web page <http://geneslinuxbox.net:6309/>
> 
> 

Cheers, Gene Heskett.
-- 
"There are four boxes to be used in defense of liberty:
  soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author, 1940)
If we desire respect for the law, we must first make the law respectable.
  - Louis D. Brandeis
Genes Web page <http://geneslinuxbox.net:6309/>