Ustream and Justin starting using
variable framerate encoding for many streams a few months ago. Remuxing variable framerate can be a little tricky. Version (2.3.2.745) of
Moyea Flv to Video Converter Pro 2 does it well.
Even for ustream streams that are not encoded with variable framerate, the fixed framerate is often different than what any tools will report, and is often an odd fixed value; like 29.968.