hi all,
first off thanks all for this awesome resource. learning a lot from here!
i’m working on a set of two modules in 4U format (with eurorack power/standards) for composite video. eventually going to dive into RGB as it is of course way more useful. but i wanted to turn all i learned from rob’s (and cyberboy’s) circuits into a couple modules.
the first is a “CVBS Decomposer” module. this module will basically strip out all the relevant CVBS signal parts to CSYNC, HSYNC, VSYNC, BACK PORCH, ODD/EVEN in 5V eurorack compatible signals (gate high) in order to be able to patch into Castle/Lunetta modules for pattern generation and such. and also ACTIVE VIDEO and COLOR BURST.
the second is a “CVBS Composer” module. this module will basically just take in sync (not certain if VSYNC+HSYNC, or just CSYNC) along with the BACK PORCH plus ACTIVE VIDEO IN and COLOR BURST IN…possibly add some bias to the AC coupled signals (BURST + ACTIVE VIDEO) and basically compose a composite signal using a multiplexer like rob+cyberboys circuits. this module would need to scale and invert the 5V sync signals and scale the color burst and active video from 1V p2p into the NTSC standard IRE sizes. and then (or at the same time) “amplify” the muxed output signal to 2V p2p through 75ohms etc.
the ACTIVE VIDEO and COLOR BURST i am not certain as to whether to make 1V p2p like all LZX module signals are. it seems if I do, then I can make a color burst module with a reference burst and phase shifted bursts as colors and just scale and mix them into the proper p2p sizes and into the composite output signal.
do these ideas make any logical sense? any issues you can foresee or advice to give?
here is a WIP circuit for the decomposer i’m going to breadboard soon.
cvbs-decomposer.pdf (159.8 KB)
