Solve this one....... Knockout series.

Once my friend asked me, do you know knockout series. I said yes. He said, "well then tell me how many matches will be played among 500 players"? If you are able to give this answer than tell me how much matches will be played among 1000 players? But in the later question if you have taken time more than 30 sec then you are gone.......

Disclaimers:: Do not see the comments unless:

1. You have solved it or
2. See first comment only if you have doubt.....