BSTR bstr=SysAllocString(L"c:\\123.avi");
hr = m_spAvi->put_FileName(bstr);
//hr = m_spAvi->put_FrameRate(100);
hr = m_spAvi->Start();
and after on every frame I call:
hr = m_spAvi->AddFrame(m_spCamera, m_spFrame);
AddFrame function returns value nonequal to S_OK, so I have empty result file

At the same place as AddFrame I call:
m_spCamera->DrawFrame(m_spFrame, Hwnd);
DrawFrame function draws the image on a window.
And one question more where I can find decription of all cameras options? OptiTrackAPI_1.1.035.doc doesn't contain information about for example NP_OPTION_MULTICAM, NP_OPTION_USER_HWND and etc.