1V DC vs 75R Video

Category: Unknown · Tags: videosignal · Posts: 5

#1 — Sailormouth · 2019-02-17

How does 1V DC signal differ from 75R Video signal? Vidiot has these distinctions in Luma and Colorizer sections.

I know LVX is driving the 1V standard, but what does that mean?

Is it simple enough to explain here or where is a good source to read up?

#2 — 48HourVideo · 2019-02-18

Hi @Sailormouth . Here are the resource that come to mind:

• The LZX Patchable Video Standard
• LZX Analog Video primer, timestamped to encoding info

Someone else will roll through with some uber deets, I’m sure – but the basics are:

• The 1V DC signal can be +/-1 volt, whereas the 75R video signal is clipped to 0V to +0.7V, so that displays can read it properly
• The 1V DC signal has no embedded sync data, whereas the 75R video signal has horizontal, vertical, and frame pulses (so the 1V video is not valid for display on anything but the Liquid TV module preview jacks)
• The 1V DC signal is pretty much a luma signal with no color subcarrier data, whereas the 75R video signal has the color subcarrier transposed on the luma signal

#3 — Sailormouth · 2019-02-18

Thank you 48HourVideo. Your response is absolutely clear and succinct. I will check out those links too.

#4 — creatorlars · 2019-02-18

The Cadet II and Cadet III schematics are functional examples of circuits that translate between the two formats. Cadet II includes the steps for 1V RGB to Composite Video encoding (black/white clipping, blanking, sync insertion, encoding) and Cadet III includes the steps for external monochrome video to 1V RGB (DC restoration clamp, 0.714X -> 1V gain scaling, high impedance output buffer, etc.)

#5 — Sailormouth · 2019-02-19

Thank you, Lars, for the extra details.