Here’s a beta release of a On Screen Display (OSD) shield I’ve been working on, it still needs a bit tiding up.
It uses a MAX7456 from Maxim for the video overlay function. The MAX7456 is connected to the Ardunio’s SPI port (MOSI, MISO and CLK) and a double row of 0.1 headers can be used to choose which digital pin drives chip select (CS) for the MAX7456.
In addition to the MAX7456 OSD chip, there’s also a DS1307 Real Time Clock (RTC) with battery backup for displaying time and date in the video feed.
For software, I used code from Arduino forum members dfraser and zitron in this Arduino forum post.