Re: RGB to Component video converter (SCART)

["Bryan Parkoff" <nospam@nospam.com>]

"nyder" <nyder.23@gmail.com> wrote in message 
1178569264.243117.134480@y5g2000hsa.googlegroups.com">news:1178569264.243117.134480@y5g2000hsa.googlegroups.com...
> On May 7, 1:00 pm, "Michael J. Mahon" <mjma...@aol.com> wrote:
>> Charlie wrote:
>> > "Michael J. Mahon" <mjma...@aol.com> wrote in message
>> >5vSdnYkGg6mtYqPbnZ2dnUVZ_q2pnZ2d@comcast.com">news:5vSdnYkGg6mtYqPbnZ2dnUVZ_q2pnZ2d@comcast.com...
>>
>> >>mdj wrote:
>>
>> >>>On May 7, 8:38 am, "Michael J. Mahon" <mjma...@aol.com> wrote:
>>
>> >>>>I was thinking that the white RCA connector could also be a sync
>> >>>>output...  But, IIRC, the SCART connector does have power, right?
>>
>> >>>Unfortunately, no. It provides stereo sound in/out, composite video 
>> >>>in/
>> >>>out, and RGB in/out. The later revisions of the standard allow the RGB
>> >>>signal pins to carry either YUV or S-Video. IIRC, YUV isn't even a
>> >>>part of the standard.
>>
>> >>>There's also pins for the D2B automation bus and a signalling pin for
>> >>>16:9/4:3 source identification.
>>
>> >>>So that white connector could also be composite sync input. Perhaps
>> >>>the power connection is obscured somehow.
>>
>> >>OK, my apologies...I thought all those RCA jacks were *outputs*!
>> >>After all, it does say RGB *to* component, and SCART is RGB, right?
>>
>> >>And it also says:
>>
>> >>* BRAND NEW; Scart (male) to Component (female) Adapter.
>> >>* For 'RGB' scart video signal to high quality 'Y/U/V' component video
>> >>  signal.
>> >>* Signal output from DVD players, Freeview, Sky or Sky+ set-top boxes
>> >>  to Component Video.
>>
>> >>That sure *sounds* like it accepts an RGB signal on the SCART side
>> >>and outputs a Component signal on the RCA side.
>>
>> >>I thought that SCART was also an *output* connector for AV equipment,
>> >>and that it would supply RGB that this box would convert to component.
>> >>(And with all those pins, not supplying a little power seems like an
>> >>oversight...)
>>
>> >>Does anyone know what this $5 thing actually does?
>> >>(I'm pretty sure that the $60 box does what I described.)
>>
>> >>In any event, this would be a straightforward way to drive a modern
>> >>TV from a IIgs RGB signal, perhaps.
>>
>> > Michael,
>>
>> > Okay, I'm a little confused.  What is the difference between RGB 
>> > component
>> > video and Y/U/V component video?
>>
>> RGB is one thing, Component is another--and Y/U/V is another way of
>> saying "component".
>>
>> "Component" is not commonly used to refer to RGB.
>>
>> RGB is three, high-bandwidth analog video signals, one per primary color
>> of the display device.
>>
>> Component refers to three analog signals:  the high-bandwidth luminance
>> signal (Y), and the (usually lower bandwidth) color difference signals
>> called B-Y (or Pb or U) and R-Y (or Pr or V).  (These different names
>> actually refer to different matrix factors used in forming the signals
>> and their levels, so they are not *really* identical, though their
>> usage is quite similar.)
>>
>> RGB is a standard native to tri-color displays and computer graphics
>> systems, while component video is native to video recording and
>> transmission systems.  Component video, with its typically reduced
>> bandwidth chroma channels, is better suited to video transmission.
>>
>> > And more important to me, would either one
>> > of the boxes (assuming they do what they advertise) give me a better 
>> > screen
>> > image than just running the IIgs output into my Monitor/TV with Roger
>> > Johnstone's IIgs to SCART cable?
>>
>> No, direct analog RGB output to an RGB input is the best you can do.
>>
>> >  As it stands now I get a usable but not
>> > perfect picture.  The only problem seems to be in the transition from 
>> > one
>> > color to another horizontally.  For instance, if you have a line of
>> > horizontal black pixels which turn to white there will be one pixel at 
>> > the
>> > transition that is gray.  This creates a horizontal ghosting effect 
>> > that can
>> > be reduced by judicious adjusting of the contrast and sharpness, but 
>> > some
>> > color combinations are worse than others.  I had the impression from 
>> > past
>> > threads that this ghosting effect was caused by the monitor not being 
>> > able
>> > to sync with the IIgs signal frequency.
>>
>> I presume you are using a digital monitor, and you are correct, the
>> "intermediate" value pixel is the result of the sampling clock of the
>> monitor not being locked to the dot clock of the IIgs.  If the pattern
>> of gray pixels is constant and consistent over the width of the display,
>> then your monitor may have locked to a multiple of the dot clock.
>>
>> > My monitor/TV (Samsung SyncMaster 940mw) will accept several types of 
>> > video
>> > input including both SCART and component video but to further confuse 
>> > me the
>> > component video input is listed as Pr, Pb, Y.
>>
>> Those are the common names for the "components" of "component video".
>>
>> The reason for my interest in good, inexpensive RGB to component
>> converters is that in the US, HD monitors typically do not have RGB
>> inputs, but they often do have component inputs.  Since component
>> signals can be created from RGB signals by analog matrixing (combination
>> with specific weighting factors), such converters are, in principle,
>> very simple.  Unfortunately, they also seem to be relatively low volume,
>> so their simplicity often is not reflected in their price.
>>
>> -michael
>>
>> NadaNet file server for Apple II computers!
>> Home page:  http://members.aol.com/MJMahon/
>>
>> "The wastebasket is our most important design
>> tool--and it's seriously underused."
>
>
>
> Does the IIGS output analog or digital RGB?
>

    Apple IIgs outputs analog RGB in the RGB video port.  If you wish to 
outputs digital RGB, you can do from the motherboard before the analog RGB 
video port.  If it is CGA monitor using IRGB, connect RGB1, RGB2, RGB4, & 
RGB8 pin on VGC chip.

Bryan Parkoff