Hello everybody,
I have found a good program which can converse voice and video into media files. It is provided by Ozeki VoIP SIP SDK and with it you can play back the pre-recorded media file into a SIP call.
If you are interested in media file conversion technologies you will find more useful information on this site
http://www.voip-sip-sdk.com/p_407-vo...ions-voip.html.
Have a nice day! ;)