How to set the .htaccess file to prevent the anonymous to play the flv

To establish a online video website similar to YouTube.

Server A:
(1) Receives the requests from the clients;
(2) Judge if the client is our customer;
(3) If it’s our customer, redirect the link to Server B with the customer’s information;

Server B: The server providing video files
(1) Once receive the request, verify the information;
(2) If it passed, provide the online play to the client.

In this case, how to set the Apache parameters of the Server B ?