reverse engineer vcr for overlay?

Question

im not an expert in NTSC video, electronics and the sort, nor do i completely understand how i could go about this...,,,, ive been good with computers and hardware... but ive got a good idea...

if any one has ever had a vcr from the 90s working or not, you will know about the various icons and text options that you could see while playing a cassette tape.... for example when you told a video to rewind, it would show the icon as its doing so on the tv.... ive got an idea but it requires an image overlay through rca connection , just like a vcr. if any one has ever taken app art a vcr and modified the so called "firmware" to display a different icon message etc, is it possible to make a custom overlay?

if any ones ever been able to take appart vcrs and know exactly how they work circut-wise, analog, digital etc, i could really use some help.... basically the most simple thing is to take a single transparent image and inject it into already existing rca footage....

1:camera-> [rca out--]
2:[-- rca in] --> overlay --> rca out --]
3 [-- rca in- screen//tv..... for viewing video]
basically im trying to make a virtual heads up display system, using cheep materials... vcrs will always be handy, and im really could use a battery powered portable board or device that can do that Imag overlay... i need help.

Answer 1

It's not hard to mix two TV signals. After all they are just analog signals that you mix like any other signals. BUT, the hard part with video is getting the two images to line up (sync). It's a process called gen-locking. You will want to look that up.

Answer 2

Yes and no.



Many older VCRs with OSD have a standalone OSD generator chip. That is often programmed with three line serial or I2C, which you can cut the lines and program with your own microcontroller.

Getting data on those chips might be impossible, especially if they are Mitsubishi or Funai house numbered.

Answer 3

the easiest and yet most sophisticated way to do this is with a computer scan converter overlay that would allow you to overlay complete pictures or text or both over live video. this is an example



http://www.bhphotovideo.com/c/product/221361-REG/AV_Toolbox_CS_450R_CS_450_Scan_Converter_with.html