From Ozeki Autodialer:
With Ozeki VoIP SIP .NET SDK you can develop C# SIP softphone for mixing/recording incoming/outgoing voice calls. The SDK also includes further softphone features such as multiple phone calls and lines, client mixed conference calls, MWI, SIP message capture, customized to your exact needs. This sample program treats each conversation the same way: all of your business or daily conversations will be recorded and saved without any loss and distortion. Don't worry about losing any minutes of important voice calls and unrecognizable voice. Recording and mixing audio are both available and can be easily developed. To mix incoming/outgoing voice calls you need to have AudioMixerMediaHandler. To record all calls WaveStreamRecorder is needed. To develop a softphone with voice call recording all you need is Ozeki VoIP SIP SDK, which is a user-friendly solution completely written in .NET, this way it provides compatibility with any .NET program. Extended codec support ensures excellent sound quality: G.711 aLaw/uLaw, G.729, iLBC, GSM, G.722, SPEEX, SPEEX-WB, L16, G723, G726-16, G726-24, G726-32, G726-40, G728. It offers you other unique possibilities for VoIP communication development with MS Silverlight/Flash softphones, webphones, DTMF IVR systems, CRM or callcenter, etc. Wide VoIP PBX compatibility is covered: Asterisk, 3CX, Kamailio, Trixbox, Elastic, FreePBX, etc, and excellent VoIP Service provider compatibility is also available: Skype Connect, Gafachi, CallCentric, SureVoIP, VoIPTalk, etc. Ozeki SDK is fully standard compliant, based on the IETF standards and meets the requirements of VoIP providers and PBX systems. The source code can be modified according to your needs in your projects. The GUI is fully customizable with company logo and company name or you can shape the outlook of your softphone according to your needs. The outstanding support assists you to create or modify your IP based telephone solutions. A purchased Ozeki SIP SDK license requires no royalties.