I don't know how Linux works,
(maybe there's a work around with this system)
but using WINdows, what you're attempting is not possible since
(1) VLC Media Player does not recognize PPs -
if the sound was actually attached -
sounds as if that may be the case -
to the PP, then you should be able to locate it in the LO
section of your computer;
(APPData -> Roaming -> LibreOffice -> 3 -> user -> Gallery ->
you'll see all audio files which you've played)
(2) if the sound was not actually attached then you will need to
return to the source for the audio file.
(3) just 'searched' for 'Son et Lumière' and located a number of
videos which might be what you seek -
one can be found
https://www.youtube.com/watch?v=NviTpDb6pEk -
(on the side are others)
(4) curiously wondering what libreoffice-avmedia-backend-gstreamer
is,