Years ago while still using windows 2000 I discovered that the difference in audio codecs was important. Far more information can be packed into formats that then take up less space than the comfortable old mp3. It may in fact have been this discovery that sent me plummeting down that hole of nerdiness which ended up with this topic about linux and audio codec manipulation on a blog (during a sunny day by a lake). No more digression!
Twelve years ago after reading the results of multiple double blind tests curated by people who care WAY more than I do about the subject, I decided on ogg vorbis which may very well be the nerdiest of all codecs. It is open source so there will always be the ability to decode it (I will never be forced to re rip all my cd’s, some of which are now unplayable). It requires more processor power than decoding an mp3, and of course it is “opensource bullshit” so it is almost never supported by hardware, meaning that I have to use alternative firmwares on all of my portable devices but that was a lifestyle change I made anyway. I secretly enjoy the unnavigable interfaces and unfriendly uncaring welcome screens that pop up on these devices, causing most people used to i-devices to put them back down.
Needless to say, ogg vorbis never really took off. Even linux nerds have skipped it in favor of flac or, out of desperation, mp3. When I am procuring music through illicit means, I of course give precedence to files encoded in vorbis but in practicality aac is just as good if not better. Every idiot out there has Itunes and a lot of them are ripping their cd’s into m4a (actually mp4). This is great because I don’t need to waste space downloading 192 kbit mp3′s that sound every bit as good, but the knowledge that they are mp3′s gnaws at me slightly and if I see the same album in flac I will download it again.
Now that you have a bunch of m4a files, what do you do with them? Well, if you run a reasonable linux distro it will play them without you having to do anything. I use exaile which supports large music collections and is responsive at the same time. It also reads replaygain tags. However, the best tools for manipulating m4a files are windows-based still.
That means you have to install Wine, the windows emulator. Then, you install foobar2000. Foobar2000 works nearly seamlessly in linux under wine. Unfortunately if you have firefox and a flash plugin open, audio won’t work with fb2k. I don’t use it for audio anyway; I find it most useful for
1. tag albums using freedb, musicbrainz and discogs (all three sources of album information work with fb2k using plugins)
2. renaming files and folders into the /music/artist/album/tracknumber – title format, unless they are multidisc or various artists releases
3. scanning the album and applying replaygain tags to them.
4. if there are no ogg vorbis or m4a files available for an album and I downloaded flac, I can convert to vorbis 5, 6, or 7 depending on how much I enjoyed the album.

Foobar2000 is slick as shit for this work. I can tag, rename and replaygain an album in under a minute while watching a movie or listening to another music player. I was worried that foobar2000, being a windows program, might mess up the filenames with some non-utf8 filenames or something but that has never happened. I completely trust this program under wine now.
m4a’s have never been completely ironed out. From the early days in linux there were efforts to provide decoders and encoders for aac/m4a/mp4 but they were always in sketchy 3rd party repositories until a few years ago. Even today while trying to burn a cd for the old lady I crashed k3b, the best cd burner under linux with a gui. K3b can’t handle m4a. It will crash without so much as an error window. Brasero will burn them but it is temperamental, only working on certain drives. I hate buying new drives so I buy old burners from a Re-Pc for pennies on the dollar; they are old, and drivers may be an issue. They rip and burn cd’s but apparently they can’t burn m4a’s for some reason.
Anyway, that is all I have to say about the subject of audio codecs except long live vorbis. Long live sonus antiqva.