i want to get some open source libraries or codes which implement VOIP using SIP?

i want to get some open source libraries or codes which implement VOIP using SIP and RTP/RTCP (from starting the session to transfering audio and video).
where can I get these ? any suggestion is much appreciated.thank you.

Asterisk

oh,thx,I should have expressed myself clearly.I just want the VOIP codes for the client side.thank you .use pjsip ? is it troublesome ? I have around 6 years experience in developing C/C++ programs including one year and a half experience in VOIP.

asterisk ,yeah,one year ago i developed some programs related to asterisk,it's a cool solution.but i just want the client side.thx.

Handling SIP is not a big pain in the ***... its a simple protocol similar to HTTP...

You can go for Sofia-SIP library which is an Opensource library.

Or use Winpcap library, get the Raw packets, and handle SIP...

You're having experience.. so, an experienced programmer would be able to do it faster than i did it within a month.. i'm only 1 and 1/2 year to programming and i used to parse and handle the Raw packets by using Winpcap :)

but using a standard library is always safe, and time saving.. :)

oh,thank you.I will check out two of these open sources.what about pjsip ? After I have checked out some of these sip open sources, I will make a decision whether to use open sources or implement the private protocols myself.:-)

I had no bad or good opinion about pjsip library since i havent tried it yet ;)

Better do some enquiry about the library to someone who had used it, and then decide whether you will be using it or not... And, i'm not at all a fan of Opensource..

And, documentation of almost all opensource libraries i'd seen concentrating on SIP sucks plainly like all other most opensource projects... so better try a library from a site who provides a fair documentation and a support forum... else, things might lead into horror.. :)