How to overlay/superimpose a line on TV ???

Hi … I would like to ask, if someone know, how to superimpose/overlay a THIN HORIZONTAL LINE on the TV so that I can move it UP and DOWN … (by external source = potentiometer, range sensor, math calculation).

I found only this - a different micro controller http://www.micro-examples.com/public/microex-navig/doc/081-pic-osd-superimposer.html . Although it superimpose text … I think I would be happy with this solution “_ _ __________” as a line. But I am the impression, that arduino should be able to do the same … or not ??? And on the PIC I don’t know, how to move the line up a down according to external source/sensor (it’s just written in the code).

Looking forward to your comments and thank you in advance.

Zholy

The tricky bit is synchronising the output to the incoming video - not a project for a beginner. You could use a sync splitter to do the leg work, giving you line interrupts that you count until you get to the line you want.

You might be able to bend the TellyMate Shield (search the forums here) to your needs. As AWOL pointed out, the tricky part is getting the sync synched. If the TellyMate can be made to do that, it would probably be fairly easy to superimpose a white bar on a video signal with a simple mixer.

Ran

sparkfun sells a board that has the maxium OSD chip on it, its abit pricey for me, but not too bad

NTSC composite in and out, with a simple interface to the arduino

Use a sink separator chip and then use the line sync pulse to trigger a monostable fitted with a pot to control the delay. Make the delay between 5 and 60 uS. Take the output of this monostable and trigger another monostable with a fixed period of say 2uS.

The output of this second monostable is mixed with the video signal. This will give you a vertical line over the video, the position is controlled by the pot and the width by the time of the second monostable.

Replace the pot with a digital pot controlled by the arduino.

Mike, he wants a horizontal line.

In a PM, I've suggested a LM1881 to do the donkey-work, providing field and line interrupts which the Arduino counts. To avoid flicker, draw the same numbered line in both fields.

This is the sort of project that really needs a 'scope to verify you don't over/under run into either of the porches or worse, into sync.

Note also that the original PIC project assumed that the monitor and source would sort themselves out wrt to impedence - it's been my experience that older, simpler CRT monitors are more forgiving of non-standard signals than are many modern, often multi-standard monitors.

he wants a horizontal line

OK same setup just trigger off the frame sync pulse, delay 60uS to 25mS for the first monostable and 64*n uS (where n= number of lines thick) for the second monostable delay.

Then if you make a horizontal and vertical line set of monostables mix the two video signals to get a square.

just trigger off the frame sync pulse, delay 60uS to 25mS for the first monostable and 64*n uS (where n= number of lines thick) for the second monostable delay.

I don't that would work - you'd be dumping over alternate displayed lines in an interlaced signal so your lines would flicker, and worse, you'd be overlaying the line syncs, so the receiver's going to get upset.

I don't that would work

Yes it does, I have used it years ago.

and worse, you'd be overlaying the line syncs, so the receiver's going to get upset.

It depends on how the monitor is receiving the sync pulses. If it is a compost sync then it depends on the characteristics of the video / sync mixer. If you are just putting the wires together then no it wouldn't lock but I have never seen a video / sync mixer that did that.

The original post is using composite video, so no, overlaying over several lines wouldn't work - the syncs will get overwritten too.

The PIC solution breaks quite a few rules (overclocked processor, mismatched impedences), but like most systems breaking rules will work...sometimes.

I have some composite CMOS cameras that claim CCIR compliance, but some of my cheaper digital LCD monitors simply won't display their output (I suspect poor field syncs), whereas a 25 year old PAL CRT monitor is perfectly happy (it even displays NTSC/RS170, albeit in mono only).

he syncs will get overwritten too.

No you have a sync separator, you mix the video back with the syncs.

This was a lab I used to get my students to do, it's not difficult.