Overlaying text onto NTSC video?

Other Hardware Displays
1

Does anyone have any tips for using an Arduino to overlay a real-time data stream onto an NTSC video signal?

My application is a downlink video system to be flown in large model rockets. My idea is to have an Arduino read the telemetry data (5V RS-232 serial, 9600 baud) from my altimeter, generate a numeric display, and overlay it onto a video signal from an onboard NTSC camera, with the combined video signal then sent to an ATV transmitter to be broadcast during the flight. A update rate of a couple times per second would be needed to be worthwhile.

The altimeter is a MARSA4, and the telemetry specs are available here:

http://www.marsa4.com/jmla/index.php?option=com_content&view=article&id=57&Itemid=62

I am using a 1/4" CCD board camera for a video source. I have seen a couple of video shields for the Arduino, but they only seem to provide a video output, not the ability to overlay onto an external video signal. Does anyone make a video output board that can accept external sync signals, so I can "genlock" the arduino generated text to the sync of the camera?

2

It may be possible to change the TVout library to use external sync pulses instead of clock generated pulses. That would be a mostly-software solution.

3

MAX7456 video overlay IC from Maxim.

Sparkfun has a breakout board: SparkFun On Screen Display Breakout - MAX7456 - BOB-09168 - SparkFun Electronics

IIRC, someone either has or is making a shield.

There's a library here: http://www.eng.uah.edu/~jdw/avr/MAX7456_lib.tar.gz

It assumes you've downloaded a different character set to the OSD's flash memory. Details are in this thread on the old forum: http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1220054359/0

I started playing with this specifically for ATV video overlay. It works well - that's what the IC is designed to do.

-j

4

I think boffin1 did something similar a while back

Rob

5

IIRC, someone either has or is making a shield.

It's been done...

http://dangerousprototypes.com/2010/05/06/video-overlay-shield-for-the-arduino/

6

@n2ixk, if you can wait a little while, I'm announcing a new Arduino shield in about 2 weeks that provides the ability to overlay text and graphics onto an NTSC signal (among many other features).

7

nootropic:
@n2ixk, if you can wait a little while, I'm announcing a new Arduino shield in about 2 weeks that provides the ability to overlay text and graphics onto an NTSC signal (among many other features).

Sounds cool, will it be using the MaX7456 OSD chip?

8

Sounds cool, will it be using the MaX7456 OSD chip?

Nope, it's a far lower cost solution than that. This overlay solution will be affordable! The shield will be around $25.

9

nootropic:
@n2ixk, if you can wait a little while, I'm announcing a new Arduino shield in about 2 weeks that provides the ability to overlay text and graphics onto an NTSC signal (among many other features).

Sounds great! No particular rush on this project, so I will be awaiting your release....

10

@n2ixk,
I just announced the product in the Products and Services board:
http://arduino.cc/forum/index.php/topic,56049.0.html

11

Nootropic:

Order placed...

Thanks!

12

I'm trying to take a more direct hack approach, by locking the Arduino 16 mHz clock to an external NTSC signal.

Would probably use a PLL (CD4046) and a varactor. Would use the amazing TVout library.

Any interest? Best. kwd... VE2KXD

13

One more project with LM1881 & Atmega8: