I have this challenge to build an sip softphone using c# or .net technologies.
Please guide me the technology, requirements and specifications that is needed to build such.
Possible requirements:
Supported codecs:
G.722.1, G.723.1, G.726, G.728, G.711, G.729, G.723.1, iLBC,: G.711 (A and m-law),G.729A/B/D/E, AMR, GSM 6.10/EFR, iLBC, Speex
Voice:
Real time Quality Monitoring (MOS) 3 independent phone lines
Auto-Answer/Do Not Disturb Call
Forwarding Full Duplex Audio
Recording compress the audio data.Fully SIP compatible softphone/dialer for PC2Phone and Mobile2Phone (iPhone, Nokia N95) application with symbian s60 , full source code should provide.
Compatible with Windows 2000/XP/2003/Vista/Mac
NAT/Firewall traversal feature
Works with any 3rd party SIP Server
Supports SIP outbound proxy
Displays callers account balance
Displays call credit time
Automatic Echo Cancellation
Automatic jitter buffer adjustment
Last number Redial
History of 10 last dialed numbers
Quick dial user list
Quick provision for customers, only user name and password required
http://www.konnetic.com is a relatively new addition. Fully managed. Everything you need to work with SIP and SDP. They haven’t picked the low-hanging fruit in the standard like a lot of the others. Just as good but tied to Microsoft is the Microsoft Lync server.
Konnetic provide fully managed SIP components for .NET development.
Their SIP .NET SDK is available here and is probably the most comprehensive. They also provide an MSRP library.
Otherwise, Microsoft's Lync server comes with a very good managed SIP library, available here: www.microsoft.com/en-us/lync/default.aspx
Microsoft Real-Time Communications: Protocols and Technologies http://technet.microsoft.com/en-us/library/bb457036.aspx
来源：https://stackoverflow.com/questions/1067692/how-to-build-a-softphone-using-sip-protocol-using-c-sharp