Ozeki VoIP SIP .Net SDK for video softphone development to make/receive voice/video calls effectively. The sample program uses the SIP softphone source implementation of Ozeki SIP SDK. The video softphone ensures excellent voice and video communication by supporting HD video phoning, jitter buffer, video codecs: H.263, H.264, picture rotate, flip 720p, svga, xvga, vga, cif, QCIF video resolution. The sample program presents how to use video devices (camera, video playback) and ensures video quality (resolution, codecs). The greatest advantage of video softphone that is developed by Ozeki SIP SDK is that there is no need to download or install any application on the client side but the clients can start video calls immediately. For video calls, the camera is the input device that captures the video data that is digitized by using standard video codecs. The output device for video communication is the video playback, i.e. the monitor, displays the video data stream. Video calls are quite similar to voice calls so only a few changes needed in the source code of the Ozeki sample softphone example since video calls uses the base of voice communication. It is extended with extra codec support and display methods. When it comes to video calls, both audio and video data are sent in a digitized and segmented from via the established phone line between the two VoIP clients. The Ozeki video softphone supports the standard video codecs so it ensures clear and smooth video and sound quality. CUSTOMIZABLE FEATURES AND GUI: You can easily customize the features and GUI of the video softphone when you use Ozeki SIP SDK. ON-LINE VOIP SERVICE SUPPORT: Ozeki SIP SDK works with almost all VoIP service providers (Skype Connect, Gafachi, Callcentric, SureVoIP, VoIPtalk, etc.) due to that it is fully standard compliant. OUTSTANDING PBX COMPATIBILITY: It is compatible with the most of PBXs such as Cisco UCM, Asterisk PBX, 3CX Phone System, Kamailio, OpenSIPS, SipX ECS, Elastix, etc.