I had some .m4a files that grew larger than I was expecting, and my debug seems to reveal that changing the cover type from Front Cover to Back Cover causes the file size to grow by 2x the size of the cover graphic. Is this expected for some strange reason?
Here's an example:
I start with an .m4a file of 1,606 KB with no graphic
I add a 551 KB graphic as a Front Cover type, and the file increases to 2,157 KB (seems normal)
I change the cover type from Front Cover to Back Cover, and the file size increases to 2,709 KB (not what I'd expect--it seems to be the original 1,606 KB file plus 2x the 551 KB graphic)
If I change the cover type back to front cover and resave, the file goes back to 2,157 KB (as I'd expect)
So far this seems quite reproducible, so is this expected due to some tagging specification, or have my files hit some strange boundary case?
In case it matters, I'm using MP3TAG v2.72 on a Windows 8.1 64-bit system.