Splitting sync-on-green video signal
in [Design]
|
From: Tim Williams on 10 Jan 2010 13:18 <a7yvm109gf5d1(a)netzero.com> wrote in message news:f7e8c633-672c-4233-b5ad-8fe3981a865c(a)m3g2000yqf.googlegroups.com... > 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) So throw in a few feet of coax. :^) Tim -- Deep Friar: a very philosophical monk. Website: http://webpages.charter.net/dawill/tmoranwms
From: mike3 on 10 Jan 2010 15:25 On Jan 10, 7:46 am, a7yvm109gf...(a)netzero.com wrote: > 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) How though would one determine the propagation delay?
From: whit3rd on 10 Jan 2010 18:50 On Jan 9, 12:58 pm, mike3 <mike4...(a)yahoo.com> wrote: > 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? Start by separating out a logic signal for 'sync'; a one-transistor amplifier, with the base DC bias set by the average collector voltage, will work. You know the sync duty cycle, just ground an NPN's emitter, put a pullup resistor to +5 on the collector, and AC-couple the video to the base, DC-couple a divided-down collector voltage to the base. Now run two PLLs on the sync signal, one for H, one for V. Finally, use a video buffer amplifier biased to clip the low SYNC level but still have unity gain for the video signal range; it's do-able.
From: Hal Murray on 10 Jan 2010 22:08 >> Otherwise they arrive before the green to the monitor. (Propagation >> delay through whatever circuitry for the green =3D time delay =3D shifted >> green picture on screen =3D> same delay for R and B to restore picture >> quality) >How though would one determine the propagation delay? Standard trick in the (old) digital days was to run both signals through similar gates. For example if you wanted to gate a clock pulse, you ran it through a x00. You also ran all the other clocks (that were supposed to happen at the same time) through a similar gate. First chioice was to put all the related gates in the same chip. Second choice was to use the same type of chip. Third choice was to use a handy gate of the same logic family. -- These are my opinions, not necessarily my employer's. I hate spam.
From: Glenn Gundlach on 11 Jan 2010 04:12
On Jan 10, 12:25 pm, mike3 <mike4...(a)yahoo.com> wrote: > On Jan 10, 7:46 am, a7yvm109gf...(a)netzero.com wrote: > > > 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) > > How though would one determine the propagation delay? Um, you measure it with a scope and a test pattern that has white (R/G/ B) vertical lines and measure the delay. You can easily get to under a nanosecond with a good scope. The delay in the green processing can be made up by shortening the cable. Any decent analog video guy can do that. G² |