Why M4a and not mp4?

[Christopher Woods (CM)]

>> Google would be your friend here. M4A and MP4 have the same container 
>> format.  The M4A extension is just a naming convention for audio-only 
>> files, a convention to which get_iplayer adheres.  For whatever 
>> reasons, some players won't recognise the M4A extension, so rename.
>
> Personally I always use the "aactomp3" flag in get_iplayer to 
> transcode the AAC file as MP3 for a radio programme. No problem 
> playing in anything that way.
>
> Chris

Yikes, enjoy that double-compressed sound? ;-) It's so ... squishy.