Splitting sync-on-green video signal
in [Design]
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From: mike3 on 10 Jan 2010 04:08 On Jan 9, 11:12 pm, Glenn Gundlach <stratu...(a)yahoo.com> wrote: > On Jan 9, 9:38 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. > > You'll nead something like the LM1881, a DC restore amplifier to > assure the DC levels and then a 'clamp amp' (clipper) to remove the > sync currently on the green. The Analog Devices AD8036 is the best > clamp amp I ever used and would remove anything below the threshold > level and drive the coax dierctly. It isn't terribly difficult but > also not trivial. You'll also need 2 gain of 2 line drivers to > distribute the red and blue. Mis-terminated analog video looks very > bad. > I sounds like this is going to take quite a few chips and other components. How much would it cost for all those components?
From: a7yvm109gf5d1 on 10 Jan 2010 09:46 On Jan 10, 4:05 am, mike3 <mike4...(a)yahoo.com> wrote: > Why does more processing need to be done on the red and blue lines, > anyway? Otherwise they arrive before the green to the monitor. (Propagation delay through whatever circuitry for the green = time delay = shifted green picture on screen => same delay for R and B to restore picture quality)
From: a7yvm109gf5d1 on 10 Jan 2010 10:25 On Jan 10, 1:12 am, Glenn Gundlach <stratu...(a)yahoo.com> wrote: > > You'll nead something like the LM1881, a DC restore amplifier to > assure the DC levels and then a 'clamp amp' (clipper) to remove the > sync currently on the green. The Analog Devices AD8036 is the best > clamp amp I ever used and would remove anything below the threshold > level and drive the coax dierctly. It isn't terribly difficult but > also not trivial. You'll also need 2 gain of 2 line drivers to > distribute the red and blue. Mis-terminated analog video looks very > bad. > > G² Not to mention the time difference. Unless the OP needs a lot of these, I'd say go buy an Extron 118 off eBay, it does all of this and they go for cheap.
From: Glenn Gundlach on 10 Jan 2010 11:56 On Jan 10, 1:05 am, mike3 <mike4...(a)yahoo.com> wrote: > On Jan 9, 11:12 pm, Glenn Gundlach <stratu...(a)yahoo.com> wrote: > > > > > > > On Jan 9, 9:38 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. > > > You'll nead something like the LM1881, a DC restore amplifier to > > assure the DC levels and then a 'clamp amp' (clipper) to remove the > > sync currently on the green. The Analog Devices AD8036 is the best > > clamp amp I ever used and would remove anything below the threshold > > level and drive the coax dierctly. It isn't terribly difficult but > > also not trivial. You'll also need 2 gain of 2 line drivers to > > distribute the red and blue. Mis-terminated analog video looks very > > bad. > > Why does more processing need to be done on the red and blue lines, > anyway? I got the mistaken(?) inpression you were sending to 2 monitors, not just one. For multiple monitors you need distribution amps. For one you don't need to do anything. G²
From: Glenn Gundlach on 10 Jan 2010 11:59
On Jan 10, 1:08 am, mike3 <mike4...(a)yahoo.com> wrote: > On Jan 9, 11:12 pm, Glenn Gundlach <stratu...(a)yahoo.com> wrote: > > > > > > > On Jan 9, 9:38 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. > > > You'll nead something like the LM1881, a DC restore amplifier to > > assure the DC levels and then a 'clamp amp' (clipper) to remove the > > sync currently on the green. The Analog Devices AD8036 is the best > > clamp amp I ever used and would remove anything below the threshold > > level and drive the coax dierctly. It isn't terribly difficult but > > also not trivial. You'll also need 2 gain of 2 line drivers to > > distribute the red and blue. Mis-terminated analog video looks very > > bad. > > I sounds like this is going to take quite a few chips and other > components. How much would it cost for all those components? If you can get into the source video and disable the sync insertion onto the green, that would be VERY EASY and nearly no cost. You might need a line driver(s) to send composite sync or H/V to the outside world. G² |