Unless the program bundled together to devices that record STRG videos can export to AVI video, there probably does not exist any 3rd part software that could convert strg to avi. As far as we know, the NMS - Novus Management System, should be capable of this transformation.
Convert E-Viewer recorded video copy backup to Audio Video Interleave movie.
We found one software available in the database for this conversion.
Microsoft Windows software - convert strg to avi on Windows
A professional CCTV solution for surveilance equipment
Convert from strg file format
The table with program actions contains information about what each program is capable of doing with their files. This may be a good pointer for further searches for certain file conversions and help you find the converter you are looking for if our search result is insufficient for you. However, it is far from perfect and may sometimes show results which are not really usable because of the nature of the software handles the files. So a conversion that appears as possible, just because of matched actions, may in fact not be possible.