M4A files (from YAMB) = slightly smaller filesize than originalAACs?

[Christopher Woods (CustomMade)]

> I've noticed this with MP4Box as well.  I think it filters 
> out ADTS frame headers when adding the AAC audio as a track 
> to the MP4 file, which would account for most of the 
> difference.  I would guess YAMB does likewise.

It seems to be non-destructive though; when re-exporting the raw streams out
of the MP4 file the resulting filesize is identical to the original file. I
*haven't* checksummed them though (just thought about doing it) - will run
QuickSFV when I get home and report the results, I'm about to leave the
office.