KnoppMyth on a 320G drive

[Lennart Sorensen]

On Wed, Dec 06, 2006 at 10:50:06PM -0500, D. Hugh Redelmeier wrote:
> Interesting.
> 
> I don't think that S-Video to RCA can be done with a simple cable.
> The signals on the wires don't match.  From Len's message:
> 
> Composite (RCA): Audio channels seperated, video signal still merged.
> 
> SVideo: Audio channels seperated, video seperated into luminance
> 	(brightness) and the chrominance (colour).  Color components
> 	still merged.
> 
> Any conversion would have to involve a more complicated circuit.

Actually according to this:
http://www.epanorama.net/circuits/svideo2cvideo.html
many conversions are really as simple as physically merging the signals.

> Can you tell us more about how you do the conversion?
> 
> I have two video cards (in two different computers) hooked up to two
> TVs.  One is an nVidia 5200 and the other is an ATI 9250.  Both have
> S-Video connectors with converters to RCA.  The converters are *not*
> interchangeable.

Many video cards have extra pins on their 'svidieo' connector, and the
extra pins have the composite signal and the adapter connects to those
extra pins.  The pinout for the extra pins are not standard and vary
from company to company.

> Standard S-Video connectors have 4 pins.
> 
> The ATI S-Video jack accepts 3 extra.  I would presume that the
> standard 4 pins carry S-Video and the extra 3 carry composite video.

Yep pretty much.

> The nVidia has the standard 4 pins.  I have no idea how the nVidia
> S-Video to Composite cable works.

They might do some detection to see if something is connected to all 4
pins, and if not, it just sends composite signal on 2 pins rather than
svideo on 4 pins.  It's possible at least.  Or maybe they convert with
the method shown in the link I sent.

> In my unscientific testing, the nVidia's composite output was not so
> hot.  I cranked the saturation control down a lot and that improved
> things to the point of being watchable.  I have not done systematic
> testing so this should not be considered definitive.
> 
> On the other hand, TVout from the ATI wasn't a piece of cake.  I
> needed a non-standard patch to the ATI driver.
>   http://megahurts.dk/rune/tv_output.html
> Apparently this is too much of a hack for xorg to adopt.

The nvout package is supposed to be quite good.  I don't real with ati's
crappy drivers any more.

--
Len Sorensen
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