Did you look at Cinelerra, linked fron the Avidemux page (under the head "Open source software similar to Avidemux")?
"Cinelerra is a highly advanced and professional video editing, but still remains open source. Cinelerra solves three main tasks: capturing, editing and compositing."
It may not satisfy all your requirements (depending, in part, on your background in AV editing), but seems to be worth a look.

In reply to Re: (OT) Blending videosources of perl talks... by ww
in thread (OT) Blending videosources of perl talks... by LanX

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