Currently, the OutputFile constructor throws a runtime exception:
https://github.com/mikrosimage/avTranscoder/blob/develop/src/AvTranscoder/file/FormatContext.cpp#L192

TODO:
https://github.com/mikrosimage/avTranscoder/blob/develop/src/AvTranscoder/file/OutputFile.hpp#L28
Remove default filename argument to empty string.
Add a constructor with a filename and a format name.