Does music under CC-SA license require the same license for video? If I use music, that is released under Creative Commons Share Alike license as background for my video, does that fact cause whole video to be derivative work, thus requiring it to be released also under CC-SA license?

Can soundtrack and video be treated as two separate works (if they are contained and released as single file)? Can different license be attached to image and sound?

It's obvious to me, that if soundtrack music is licensed under CC BY-NC-SA (Creative Commons, Attribution, Non-commercial, Share Alike), whole work cannot be used commercially, because that would break the Non-commercial clause of soundtrack. And then I would like to release video part with ND (No Derivatives) clause, so it could only be used unaltered.
From the by-sa legal terminology:


  Section 1 – Definitions.
  
  Adapted Material means material subject to Copyright and Similar Rights that is derived from or based upon the Licensed Material and in which the Licensed Material is translated, altered, arranged, transformed, or otherwise modified in a manner requiring permission under the Copyright and Similar Rights held by the Licensor. For purposes of this Public License, where the Licensed Material is a musical work, performance, or sound recording, Adapted Material is always produced where the Licensed Material is synched in timed relation with a moving image.


In other words, using it as a sound track in a video makes the video a derivative work and requires share-alike unless that provision of the license is unenforceable in your local jurisdiction.  (ie, still see a lawyer, but you most likely must share alike the video.)