You can see on many T.V channel's when The Host is on the Screen then they play som videos behind him or put some video scene behind him
i ever wanted to do that .
i have so can anyone tell me what technology they use or what can i do when i shoot with my camera or is it possibile do this stuf in Vegas
infact masking is very difficult thing well i think they do not use masking in it so plz any suggessions
Simply put, you shoot the host with a plain colour background, usually blue or green, then use the Chroma Key FX to make that colour transparent.
There are lots of finer points, such as separating the subject from the screen, lighting screen and subject separately, using back light etc, but the simplest way to experiment, is to shoot someone or something with clear blue sky behind them (if you have the climate!), then removing the blue.
The background that shows behind the subject is whatever you put on a lower track or tracks.