Similarly to .WMA and .WMV files (bug 36635) also .AAC (Advanced Audio Coding) files are missing in the list of supported file types in "Insert" -> "Movie and Sound"
However, like WMA and WMV files, also AAC files work nicely in LibreOffice. You only cannot select them from the list in the insert dialog.
Solution: Please add .aac files to the list of supported file types. I assume this is a very easy hack.
How to reproduce:
* Please download a sample .aac file, e.g. from here http://chomikuj.pl/Pikus1961/Triangle,154432734.aac
* Try to insert it in a LibreOffice presentation via "Insert" -> "Movie and Sound". -> You will not find the file.
* Instead, rename the file form Triangle.aac to Triangle.mp4. Now you can select the file and it plays nicely in LibreOffice Impress.
Just combined the two, submitting a patch now
*** This bug has been marked as a duplicate of bug 36635 ***