I am running the latest version of GTalk (using the Talk installer from the market) on my Gingerbread Galaxy Tab P1000.
I now want to programatically initiate a vid
Sorry, this is not supported. Digging in to an application like that is looking at its implementation details; unless you get documentation from the author of the application of what interactions with it are supported, the best you can do is come up with code that is likely to break at any point in the future when that application is updated.