VOIP Calling Application Developement

Here is a brief of the expertise we need, and the problem we are facing at the moment. Required Skill-set : 4-5+ years of hands-on experience in C++, C#. Exp in Building 3rd party libraries in C++ Strong proficiency in Visual Studio - 2015/2017, MSYS2, CMake Experience in integrating C++ application with C# Thorough knowledge of VOIP calling application development Understanding of SIP protocol Console/ WPF app-building expertise Current Project Requirement: The primary need is to replace the Opal library with the Linphone library to make few webcams compatible with VOIP calls. To cater to the above, we need to build linphone SDK and create DLLs Further, an internal C++ console application is to be built to have all the VOIP functionalities along with an interface layer to access this in the C# desktop application. De-bugging: Successful building of the linphone SDK and the C++ application to implement multiple VOIP features from the linphone library. Time required to implement: ~1 month P.S: Where we are stuck: We are not able to build the linphone SDK or set-up the C++ application. We are stuck at having a basic set-up/Implementation of linphone working (This is required to enable the voice calls in the C++ application) To do so, we first need to object of Core class. To create this object, SDK internally used a file called vcard_grammer. The program is supposed to fetch/ find the file to create and the object. We do have the file, but this program is not able to find it.