Splitting sync-on-green video signal
in [Design]
|
From: a7yvm109gf5d1 on 10 Jan 2010 00:16 On Jan 9, 5:09 pm, mike3 <mike4...(a)yahoo.com> wrote: > > Hmm. But how about not only extracting the sync but also removing > it from the green line to get a pure green signal? In other words, > have > something where the input is the green+sync, the outputs horizontal > and vertical sync and also pure green component (no sync)? Clamp the black level and subtract it from the video, this will bring the video down by the 0.3V (IIRC) of the usual black level, but like John said, why? It makes the circuit complex and you don't see the syncs anyways so why remove them?
From: mike3 on 10 Jan 2010 00:38 On Jan 9, 10:16 pm, a7yvm109gf...(a)netzero.com wrote: > On Jan 9, 5:09 pm, mike3 <mike4...(a)yahoo.com> wrote: > > > > > Hmm. But how about not only extracting the sync but also removing > > it from the green line to get a pure green signal? In other words, > > have > > something where the input is the green+sync, the outputs horizontal > > and vertical sync and also pure green component (no sync)? > > Clamp the black level and subtract it from the video, this will bring > the video down by the 0.3V (IIRC) of the usual black level, but like > John said, why? > It makes the circuit complex and you don't see the syncs anyways so > why remove them? Because I need to use this with monitors that do not support sync on green. None of the monitors I have are listed as supporting sync on green, and I think there aren't many models of monitors that actually do, are there? I've got an HNC AH191A monitor and Acer X223W, neither of which ring up anything when searching for them plus "sync on green" on Google. I don't want to get rid of the sync, just split it off into separate lines, like the monitor requires, and send it a pure green signal down its green port, as it requires. That is, to make a thingy that takes in the combined green+sync signal in one end and yields horizontal, vertical, and pure green component signals out the other.
From: mike3 on 10 Jan 2010 00:51 On Jan 9, 10:38 pm, mike3 <mike4...(a)yahoo.com> wrote: > On Jan 9, 10:16 pm, a7yvm109gf...(a)netzero.com wrote: > > > On Jan 9, 5:09 pm, mike3 <mike4...(a)yahoo.com> wrote: > > > > Hmm. But how about not only extracting the sync but also removing > > > it from the green line to get a pure green signal? In other words, > > > have > > > something where the input is the green+sync, the outputs horizontal > > > and vertical sync and also pure green component (no sync)? > > > Clamp the black level and subtract it from the video, this will bring > > the video down by the 0.3V (IIRC) of the usual black level, but like > > John said, why? > > It makes the circuit complex and you don't see the syncs anyways so > > why remove them? > > Because I need to use this with monitors that do not support sync on > green. None of the monitors I have are listed as supporting sync on > green, and I think there aren't many models of monitors that actually > do, > are there? I've got an HNC AH191A monitor and Acer X223W, neither > of which ring up anything when searching for them plus "sync on green" > on Google. I don't want to get rid of the sync, just split it off into > separate > lines, like the monitor requires, and send it a pure green signal down > its > green port, as it requires. That is, to make a thingy that takes in > the > combined green+sync signal in one end and yields horizontal, vertical, > and pure green component signals out the other. As I've heard if you try and send a green with sync on green in it through a monitor that doesn't support it, it'll fill the screen with lots of green hue, or the monitor might not work right, etc.
From: a7yvm109gf5d1 on 10 Jan 2010 00:58 On Jan 10, 12:38 am, mike3 <mike4...(a)yahoo.com> wrote: > On Jan 9, 10:16 pm, a7yvm109gf...(a)netzero.com wrote: > > > On Jan 9, 5:09 pm, mike3 <mike4...(a)yahoo.com> wrote: > > > > Hmm. But how about not only extracting the sync but also removing > > > it from the green line to get a pure green signal? In other words, > > > have > > > something where the input is the green+sync, the outputs horizontal > > > and vertical sync and also pure green component (no sync)? > > > Clamp the black level and subtract it from the video, this will bring > > the video down by the 0.3V (IIRC) of the usual black level, but like > > John said, why? > > It makes the circuit complex and you don't see the syncs anyways so > > why remove them? > > Because I need to use this with monitors that do not support sync on > green. None of the monitors I have are listed as supporting sync on > green, and I think there aren't many models of monitors that actually > do, > are there? I've got an HNC AH191A monitor and Acer X223W, neither > of which ring up anything when searching for them plus "sync on green" > on Google. I don't want to get rid of the sync, just split it off into > separate > lines, like the monitor requires, and send it a pure green signal down > its > green port, as it requires. That is, to make a thingy that takes in > the > combined green+sync signal in one end and yields horizontal, vertical, > and pure green component signals out the other. I'm no expert on monitors, the last time I played with S.O.G. was with an Amiga and a Commodore 1950 monitor... Gives you an idea of the time frame. I don't think a monitor would care if there are syncs or not on the green. I think the "not supported" means the monitor can't extract syncs from green (cost cutting), not that it will harm the monitor. However you could look for an Extron box called a 118 on eBay, for about 20$ it does all this stuff for you. 20$ or days of fudging around... You choose! www.extron.com/download/files/userman/rgb118series-man.pdf
From: Glenn Gundlach on 10 Jan 2010 01:06
On Jan 9, 5:55 pm, who where <no...(a)home.net> wrote: > On Sat, 9 Jan 2010 13:04:34 -0800 (PST), a7yvm109gf...(a)netzero.com > wrote: > > >On Jan 9, 3:58 pm, mike3 <mike4...(a)yahoo.com> wrote: > >> Hi. > > >> How could one make an electronic circuit that would split the green > >> signal from a "sync on green" source (like what comes out of some > >> types of computers) into the green, horizontal, and vertical sync > >> components individually? > > >http://www.national.com/mpf/LM/LM1881.html#Overview > > oooh, no! That chip is downright evil. > > [O/T] We used them in an olde (pre-GPS) frequency reference, to > extract the sync pulses from rubidium-locked TV transmissions. It > gave spurious pulses, and on further investigation this proved to be > unavoidable. We switched to the Gennum GS4981 and the problem was > history. Nah, it's just crappy. They worked considerably better with bigger coupling caps and smaller (?) resistor for the burst flag timing. I haven't touched the HD version which might be better for the higher resolutions. G² |