Re: RGB to Component video converter (SCART)

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

"Michael J. Mahon" <mjmahon@aol.com> wrote in message 
HvidnfuI6cHzldzbnZ2dnUVZ_vyunZ2d@comcast.com">news:HvidnfuI6cHzldzbnZ2dnUVZ_vyunZ2d@comcast.com...
> Bryan Parkoff wrote:
>> "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.
>
> However, that is a 4-/4-/4-bit "digital RGB", which is not what the
> common term "digital RGB" means in the retrocomputing world: three
> digital (1-bit) lines for R, G, and B, plus one 1-bit line for
> "modified intensity".  There is the so-called CGA RGBI standard, and
> the somewhat different Apple II RGBI standard.
>
Michael

    I mean only ONE bit on RGB1, RGB2, RGB4, & RGB8 pins.  They can be used 
for CGA RGBI.  If you need 4 bit digitial to 1 bit analog converter, you can 
always connect VID0, VID1, VID2, VID3, VID4, VID5, VID6, VID7, VID8, VID9, 
VID10, & VID11 pins from VGC chip.
    RGB1, RGB2, RGB4, & RGB8 can be RED, GREEN, BLUE & INTENSITY.

Bryan Parkoff