A simplistic VGA to XYZ-scope converter like this: <http://www.electronixandmore.com/projects/vgatoscope/index.html> just uses a passive resistor network to linearly scale the RGB components and sum them to monochrome. However I don't think this really works for a "modern" SVGA output because the gamma will be wrong; you have to apply a nonlinear gamma-expanding transform prior to intensity-scaling a la: <https://en.wikipedia.org/wiki/Grayscale#Converting_color_to_grayscale> Is there any off-the-shelf IC or circuit that does this or are you basically looking at using a DSP or FPGA to do it properly.
RGB to XYZ
Started by ●September 2, 2021
Reply by ●September 2, 20212021-09-02
On 9/2/2021 2:19 PM, bitrex wrote:> A simplistic VGA to XYZ-scope converter like this: > > <http://www.electronixandmore.com/projects/vgatoscope/index.html> > > just uses a passive resistor network to linearly scale the RGB components and > sum them to monochrome. > > However I don't think this really works for a "modern" SVGA output because the > gamma will be wrong; you have to apply a nonlinear gamma-expanding transform > prior to intensity-scaling a la: > > <https://en.wikipedia.org/wiki/Grayscale#Converting_color_to_grayscale> > > Is there any off-the-shelf IC or circuit that does this or are you basically > looking at using a DSP or FPGA to do it properly.Why not change the source signal being generated? Or, are you "stuck" with someone else's signal?
Reply by ●September 2, 20212021-09-02
On 9/2/2021 7:56 PM, Don Y wrote:> On 9/2/2021 2:19 PM, bitrex wrote: >> A simplistic VGA to XYZ-scope converter like this: >> >> <http://www.electronixandmore.com/projects/vgatoscope/index.html> >> >> just uses a passive resistor network to linearly scale the RGB >> components and sum them to monochrome. >> >> However I don't think this really works for a "modern" SVGA output >> because the gamma will be wrong; you have to apply a nonlinear >> gamma-expanding transform prior to intensity-scaling a la: >> >> <https://en.wikipedia.org/wiki/Grayscale#Converting_color_to_grayscale> >> >> Is there any off-the-shelf IC or circuit that does this or are you >> basically looking at using a DSP or FPGA to do it properly. > > Why not change the source signal being generated? Or, are you > "stuck" with someone else's signal? >Nah. Just thinking about how you would do it from the output of a video adapter on a relatively modern PC, so what do we have to work with. HDMI would that be easier? Maybe but I don't know enough to know. Might be easier to work with composite and there are surely off-the-shelf solutions that do HDMI to composite, and then strip the syncs and luma from that. XYZ to VGA boxes seem relatively available for e.g. radars but don't see much commercial for the other way, the demand would seem very little.
Reply by ●September 3, 20212021-09-03
On 9/2/2021 6:36 PM, bitrex wrote:>>> Is there any off-the-shelf IC or circuit that does this or are you basically >>> looking at using a DSP or FPGA to do it properly. >> >> Why not change the source signal being generated? Or, are you >> "stuck" with someone else's signal? > > Nah. Just thinking about how you would do it from the output of a video adapter > on a relatively modern PC, so what do we have to work with. > HDMI would that be easier? Maybe but I don't know enough to know.HDMI is purely digital. So, nothing like combining with a weighted resistor network would work. OTOH, you could likely directly *digitally* process the signals instead of first having to map the analog VGA signals into that domain (if you had the processing power to handle it, there -- the data rates are very high!). The same sort of argument can be used for DP or DVI-D.> Might be easier to work with composite and there are surely off-the-shelf > solutions that do HDMI to composite, and then strip the syncs and luma from that. > > XYZ to VGA boxes seem relatively available for e.g. radars but don't see much > commercial for the other way, the demand would seem very little.So, other than as an intellectual exercise, what is your motivation for exploring such a "converter"? I.e., what got you thinking along those lines in the first place?
Reply by ●September 3, 20212021-09-03
On 9/3/2021 10:41 AM, Don Y wrote:> On 9/2/2021 6:36 PM, bitrex wrote: > >>>> Is there any off-the-shelf IC or circuit that does this or are you >>>> basically looking at using a DSP or FPGA to do it properly. >>> >>> Why not change the source signal being generated? Or, are you >>> "stuck" with someone else's signal? >> >> Nah. Just thinking about how you would do it from the output of a >> video adapter on a relatively modern PC, so what do we have to work with. >> HDMI would that be easier? Maybe but I don't know enough to know. > > HDMI is purely digital. So, nothing like combining with a weighted > resistor > network would work. > > OTOH, you could likely directly *digitally* process the signals instead of > first having to map the analog VGA signals into that domain (if you had > the processing power to handle it, there -- the data rates are very high!). > > The same sort of argument can be used for DP or DVI-D. > >> Might be easier to work with composite and there are surely >> off-the-shelf solutions that do HDMI to composite, and then strip the >> syncs and luma from that. >> >> XYZ to VGA boxes seem relatively available for e.g. radars but don't >> see much commercial for the other way, the demand would seem very little. > > So, other than as an intellectual exercise, what is your motivation for > exploring such a "converter"? I.e., what got you thinking along those > lines in the first place?<https://youtu.be/PBtETkJeqmY> Love to have one, but guaranteed I'd never find one. I expect the CRT in the commercial device uses magnetic deflection, and looks like they shield the crap out of it. A round CRT would give an even better Cold War bunker-aesthetic
Reply by ●September 3, 20212021-09-03
On 9/3/2021 10:50 AM, bitrex wrote:> On 9/3/2021 10:41 AM, Don Y wrote: >> On 9/2/2021 6:36 PM, bitrex wrote: >> >>>>> Is there any off-the-shelf IC or circuit that does this or are you >>>>> basically looking at using a DSP or FPGA to do it properly. >>>> >>>> Why not change the source signal being generated? Or, are you >>>> "stuck" with someone else's signal? >>> >>> Nah. Just thinking about how you would do it from the output of a >>> video adapter on a relatively modern PC, so what do we have to work >>> with. >>> HDMI would that be easier? Maybe but I don't know enough to know. >> >> HDMI is purely digital. So, nothing like combining with a weighted >> resistor >> network would work. >> >> OTOH, you could likely directly *digitally* process the signals >> instead of >> first having to map the analog VGA signals into that domain (if you had >> the processing power to handle it, there -- the data rates are very >> high!). >> >> The same sort of argument can be used for DP or DVI-D. >> >>> Might be easier to work with composite and there are surely >>> off-the-shelf solutions that do HDMI to composite, and then strip the >>> syncs and luma from that. >>> >>> XYZ to VGA boxes seem relatively available for e.g. radars but don't >>> see much commercial for the other way, the demand would seem very >>> little. >> >> So, other than as an intellectual exercise, what is your motivation for >> exploring such a "converter"? I.e., what got you thinking along those >> lines in the first place? > > <https://youtu.be/PBtETkJeqmY> > > Love to have one, but guaranteed I'd never find one. > > I expect the CRT in the commercial device uses magnetic deflection, and > looks like they shield the crap out of it. > > A round CRT would give an even better Cold War bunker-aestheticBut an attempt to homebrew-transplant something like a commercial mini-TV guts into an enclosure that fits the form factor seems doomed, even if you could find a small enough CRT TV, the PCB and electronics would be unlikely to fit. Sounds like a hopeless and potentially pretty hazardous operation. Anything homebrew would never be as nice as the commercial product with a likely custom flyback and PCB. But there are little electrostatic CRTs people use for scope-clocks and stuff you could run the graphics card output to.
Reply by ●September 3, 20212021-09-03
On 9/3/2021 7:50 AM, bitrex wrote:>> So, other than as an intellectual exercise, what is your motivation for >> exploring such a "converter"? I.e., what got you thinking along those >> lines in the first place? > > <https://youtu.be/PBtETkJeqmY> > > Love to have one, but guaranteed I'd never find one.You are interested in the novelty? Or the functionality? This is similar to the MAME mindset -- do you want to *play* the game? Or, *own* the game? Do you want to own an IMSAI? Or, would a replica be acceptable? E.g., I've been machining a HAL9000 (I/O port) replica for use at my front door. While I'd love to have the genuine article, I realize that to be a silly goal (how many mockups were made?). And, even a "faithful replica" is silly -- the lens used is wicked expensive! And, the image processing would be unnecessarily complex. As folks coming to the door wouldn't be aware -- nor care! -- of what's behind the outer facade, what value is there for the genuine article?> I expect the CRT in the commercial device uses magnetic deflection, and looks > like they shield the crap out of it. > > A round CRT would give an even better Cold War bunker-aestheticYou could repurpose the display out of an old 'scope and drive it with a raster.
Reply by ●September 3, 20212021-09-03
On 9/3/2021 8:12 AM, bitrex wrote:>> I expect the CRT in the commercial device uses magnetic deflection, and looks >> like they shield the crap out of it. >> >> A round CRT would give an even better Cold War bunker-aesthetic > > But an attempt to homebrew-transplant something like a commercial mini-TV guts > into an enclosure that fits the form factor seems doomed, even if you could > find a small enough CRT TV, the PCB and electronics would be unlikely to fit. > Sounds like a hopeless and potentially pretty hazardous operation. > > Anything homebrew would never be as nice as the commercial product with a > likely custom flyback and PCB. But there are little electrostatic CRTs people > use for scope-clocks and stuff you could run the graphics card output to.Years ago (35?), I used a small OEM CRT in a product. No idea if it was "small enough" for THIS application. But, I had considered installing one in my car (at the time) as a foundation for a digital dash. When you think about the space available, there, it's likely it *was*!
Reply by ●September 3, 20212021-09-03
On 9/3/2021 8:47 AM, bitrex wrote:> On 9/3/2021 11:24 AM, Don Y wrote: >> On 9/3/2021 7:50 AM, bitrex wrote: >>>> So, other than as an intellectual exercise, what is your motivation for >>>> exploring such a "converter"? I.e., what got you thinking along those >>>> lines in the first place? >>> >>> <https://youtu.be/PBtETkJeqmY> >>> >>> Love to have one, but guaranteed I'd never find one. >> >> You are interested in the novelty? Or the functionality? >> >> This is similar to the MAME mindset -- do you want to *play* >> the game? Or, *own* the game? >> >> Do you want to own an IMSAI? Or, would a replica be acceptable? > > Frankly (as often happens) pondering about how to do SVGA to XYZ conversion > properly has become the more interesting problem to think about, lolThan *what*?>> E.g., I've been machining a HAL9000 (I/O port) replica for use at >> my front door. While I'd love to have the genuine article, I >> realize that to be a silly goal (how many mockups were made?). > > Yikes, I try not to scare people away (yea it's revealed Hal's intentions were > decent all along but he had some bugs, IIRC.) Maybe I'd do SAL9000: > > <https://youtu.be/PBtETkJeqmY>I doubt anyone would be scared away if they encountered a glowing red eye adjacent to the front door! Rather, those old enough to recognize it would likely chuckle. Plus, it gives me a place to mount a camera, in lieu of a doorbell button! (And, if it scares away the LDSers and JW's, well... call that a bonus!)
Reply by ●September 3, 20212021-09-03
On 9/3/2021 2:58 PM, Don Y wrote:> On 9/3/2021 8:47 AM, bitrex wrote: >> On 9/3/2021 11:24 AM, Don Y wrote: >>> On 9/3/2021 7:50 AM, bitrex wrote: >>>>> So, other than as an intellectual exercise, what is your motivation >>>>> for >>>>> exploring such a "converter"? I.e., what got you thinking along those >>>>> lines in the first place? >>>> >>>> <https://youtu.be/PBtETkJeqmY> >>>> >>>> Love to have one, but guaranteed I'd never find one. >>> >>> You are interested in the novelty? Or the functionality? >>> >>> This is similar to the MAME mindset -- do you want to *play* >>> the game? Or, *own* the game? >>> >>> Do you want to own an IMSAI? Or, would a replica be acceptable? >> >> Frankly (as often happens) pondering about how to do SVGA to XYZ >> conversion properly has become the more interesting problem to think >> about, lol > > Than *what*? > >>> E.g., I've been machining a HAL9000 (I/O port) replica for use at >>> my front door. While I'd love to have the genuine article, I >>> realize that to be a silly goal (how many mockups were made?). >> >> Yikes, I try not to scare people away (yea it's revealed Hal's >> intentions were decent all along but he had some bugs, IIRC.) Maybe >> I'd do SAL9000: >> >> <https://youtu.be/PBtETkJeqmY> > > I doubt anyone would be scared away if they encountered a glowing red eye > adjacent to the front door! Rather, those old enough to recognize it > would likely chuckle. > > Plus, it gives me a place to mount a camera, in lieu of a doorbell button! > > (And, if it scares away the LDSers and JW's, well... call that a bonus!)Their religions are half science-fiction anyway, how's it going to scare them away.
