ABTO Software VoIP SIP SDK provides a solution to quickly build VoIP softphone that can dial and receive calls on your computer or add VoIP features into your software. Quick facts about VoIP SIP SDK for iPhone: iOS 5 compatible Support of SIP and RTP STUN and other IETF standards (compatible with SER, OpenSER and Asterisk) SIP Registrar (SIP server) support Voice and video calls Status messages Available codecs: G.711-ALaw G.711-muLaw G.729 Speex Theora GSM H.263 H.263+ H.264