VirtualDub works as a basic video capture/ processing tool, being aimed at mainstream video modifications, thus integrating batch processing technology that can be applied at a large number of files. Third party filters may contribute to these capabilities. It is manly designed to handle AVI files, not being able to write in formats like MPEG-1.
Capture video from external devices, adjust frame rates, normalize sound, and do other pre- and post-processing actions without the skills of an advanced user. Tests speak for fast processing and good reliability.
And we should also consider that it was developed by a single person over a short amount of time.