Fast Video Download and Flash Video Downloader, both Firefox plugins, seem to keep up with whatever youtube might be doing.  I've never ended up with any problems with videos I've downloaded using them.  They do usually save to mp4 format, however.  At any rate, they've worked well enough that I wasn't even aware Youtube was pulling tricks with their formatting.  :unsure:

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Cage can be an opinionated jerk who posts without thinking.  He apologizes for this.  He's honestly not trying to be a turkeyhead.

Cage had some freebies, compatible with Poser 11 and below.  His Python scripts were saved at archive.org, along with the rest of the Morphography site, where they were hosted.