wallge wrote:
> I use VHDL and altera FPGAs.
> But the FPGA vendor shouldnt really matter much.
> I have VGA video stream coming into the system
> at just over 25Mhz at 60FPS at 640 x 480 valid pixels.
> Currently I am sending output to a frame grabber via
> camera link style output.
> It would be nice if there was some code out there that was
> video format agnostic - it wouldnt care about the video timing
> to be able to insert a white (or black) pixel here and there to form
> the letters
> of ascii text I am trying to achieve.

You wont be able to be video-format-agnostic for a number of
reasons :

To properly CHAR insert you need to phase-lock to the incomming Line
Sync
(often called GenLock) - if you do not do this, the chars jitter about
as you
have two clock domains.

You also need to Sync to Frame, and count lines, to decide when to
start the CHAR insert-stream.

Some of the better designs insert CHARs with a drop-shadow, so they are

readable over a wider range of backgrounds.

Teletext chipsets, and OnScreenDisplay chips, as others have
mentioned,
are a good design referance for the sync-side of things
-jg.