title: VoIP/SIP Soft Phone C# WPF
body: <p>I need to write VoIP/SIP Soft Phone in C# using WPF interface with Audio support only.
  I need to have call transfer, call conference, and recording of conversations in mp3.</p>
  
  <p>I've looked at VoIP SDK from ABTO LLC, but it is slow at application startup (30 seconds to start application, I think it's related to loading activex part of this sdk).</p>
  
  <p>I've also looked at SIP.Net, but it's only for SIP and doesn't contain components for voice data transfer. </p>
  
  <p>I have very limited time only 2 months from zero to fully working app. </p>
  
  <p>What SDK can I use to accomplish this task?</p>
  
  <p>Windows 7 must be supported.</p>