[Coco] composite / s-video to hdmi

[John E. Malmberg]

On 12/16/2012 11:48 PM, Gene Heskett wrote:
> On Monday 17 December 2012 00:26:02 John E. Malmberg did opine:
>
>> Which means that they can handle the 15.75 NTSC time signal.
>
> Thru the composite jack?  Have you ever tried to read the coco3's 80 column
> screen thru a composite hookup, or on an ntsc tv?  Difficult if not near
> impossible.  The bandwidth in the NTSC circuit simply is not there.

No, through the SVGA jack.

>> There are reports that the COCO 3 could work with Multi-sync monitors if
>> they supported 15.75 Khz sync, and I previously posted a link.
>
>> And all the flat screen TVs that I have come with an SVGA connector.
>
> Which, with Chris Hawks adapter, should work noticeably better than any
> composite setup, whether direct composite or rf modulated composite.

If the TV supports 15.75 Khz, then it probably supports it through the 
SVGA jack.

The reason it was scarce in computer monitors is that it required a more 
expensive flyback circuit.

But as you know, there is no flyback circuit in modern LCD TVs.  So no 
real reason for the multi-sync circuit to not support 15.75 Khz from any 
the sources on the TV.

Now this also may be something that works in most TVs and not others. 
It just may depend on what is cheaper, having the multi-sync circuit 
work down to NTSC frequencies or having to double the NTSC lines from 
the composite video stream.  My guess would be not having the doubler 
circuit would be cheaper.

>> Unfortunately my COCOs are still boxed up, so I have not been able to
>> try it a SVGA to COCO cable to see if it just works.
>>
> Don't forget John, that I am a broadcast engineer, who has been making sure
> there was a picture there when you turned on the tv, from 1962 to 2002, 40
> years.

I only did the broadcast engineering for my last year of college, about 
1981 to 1982.  To give you a hint as to where, along with the TV 
transmitter at the site I was at, there also was the most powerful 
commercial FM transmitter in the U.S.

Regards,
-John