On Screen Displays with TV's

[grdthato]

Does anyone know how an On Screen Display works? For example, comcast digital cable. How are text, menus, and graphics displayed and overlayed? What type of electronics are needed to do this?

 

[Nigel Goodwin]

Does anyone know how an On Screen Display works? For example, comcast digital cable. How are text, menus, and graphics displayed and overlayed? What type of electronics are needed to do this?

It's normally done with a "genlock", a device which syncronises the two video streams and combines and overlays them. In professional TV production it's even easier (or at least was!), all cameras and equipment were syncronised to a common sync source, so you could use fairly simple video mixers to do it.

If you just want to add an On Screen Display?, there are various OSB chips manufactured, specifically to put text on video signals - most TV's, VCR's and Satellite Receivers use them.

 

[Exo]

The **broken link removed**
was my favourite, but like all OSD chips, no longer manufactured.
So if you want one you'll need to find it from someone who has it still stocked.

If Nigel knows a current OSD chip that is still manufactured I would like to know too

 

[grdthato]

Basically how can I display a logo over NTSC video that is cheap and can be used as a standalone device?
Could I use this https://www.electro-tech-online.com/custompdfs/2005/08/T310-low.pdf ?

 

[Nigel Goodwin]

Have a look at https://www.blackboxcamera.com/stv5730a/stv5730a.htm, as far as I'm aware they only sell kits, and NOT just the chip - as Exo suggested, manufacture of OSD chips never lasts for very long.

I designed an OSD board around an NEC chip a number of years ago, and Dontronics was going to produce a board for it, but NEC discontinued the chip. The replacement chip was different, and I was never able to get even a sample of it :cry: