Hi everyone,
M4A has been annoying me for a while now, and since various searches on Google didn't provide satisfactory answers...
I have a bunch of M4A files that either have audio in AAC or FLAC. I am not at all into Itunes and therefore don't understand why anyone would want to package an audio format into another format. To me, packing AAC in M4A sounds like zipping FLAC files and then asking your computer to play everything from the ZIP. So I was wondering, is there a way to just extract all the M4A content without having to reconvert everything? For some reason, M4A files take ages to load in Media Player Classic (I'm having to use this player for braille reasons and it works splendidly with every other format, even Blu-Ray).

M4A would have ALAC and not FLAC.

M4A only supports AAC or ALAC, since they're both Apple formats. AAC is losy while ALAC is lossless (like FLAC).

Raw AAC cannot be recognized/played very well in most software, so it needs to be contained in M4A. While some can read/play raw AAC, it's still better when it's contained, as you can have AAC-LC (low complexity) or AAC-HC (high complexity), both are different compressions and algorithms of the same format.
AAC-LC is the most common, and what iTunes uses.
And most users here use iTunes as their media player, since it shows tags and cover art more nicely than most other players (MPC-HC is very new to "cover art" and in its experimental stages for "cover art").
ALAC to FLAC is an easy transcode. Since it's lossless to lossless.

M4A is a container, not format.
It contains either ALAC (Apple Lossless Audio Codec) format or AAC (Advanced Audio Coding) format.

The only M4A content you should transcode to FLAC are the ones that are ALAC (not AAC).

MPC is not a rich music player, it was never intended to be.
But it can play AAC/ALAC formats, even FLAC formats.

It's prilmarily intended to be a movie player, including blu-ray.
Music is a surprise.

So, in short:
Leave AAC/M4A alone.
Convert ALAC/M4A to FLAC.

And learn foobar2000.
It can do ALAC to FLAC.

Thanks, much appreciated! Yes, MPC does an amazing job with audio files. It works with almost every decoder I found, simulates 5.1 surround with stereo sources and most importantly doesn't require too much CPU or RAM. Foobar I have, I'll check it out.

MPC going from stereo to 5.1 is probably due to internal codecs with/or a combination with FFDShow.
MPC uses LAV Filters internally, which can allow you to upmix audio if oyu want.
Or you can use it decode as-is and then use FFShow to remix channels as you wish.

It does amazing with audio files because audio doesn't need so much.
Most are stereo in common formats (MP3, AAC, ALAC, FLAC, etc).

Foobar2000 can do exactly the same.

Except, since you're so familiar with MPC, it won't be as great because you never used FB2K first and are required to learn it.

It's the same hype people place upon VLC and Winamp.
They're all the same as far as functionality.
It's just that some allow more customization and user interface functionality over the other.

Winamp can allow for some nice DSP functions (from third-parties) but it's now been killed off.
FFShow can use some of Winamps DSP's and other effects, if Winamp is installed.
Foobar2000 can also use VST effects and DSP effects.
MPC uses LAV Filters and can push to FFDShow filters, which FFDShow has more functions to play with.

After that point, it's mostly up to what you use and what gets updated.
Winamp is dead with no more updates.
VLC is updated about once a year.
FB2K and MPC-HC are updated much more frequently.
LAV filters, for that matter (MPC-HC internal filters).

Any chance you could explain how I convert M4A to FLAC with foobar without losing any quality? I can't figure out which Flac level (1-8) I should use.

FLAC level 8 is most compression, smaller file.

But you don't lose quality on any compression level.

Everyone uses level 8 for FLAC compression.
If you convert to level 8 and level 8 then convert both of those to WAV and bit-compare those two, they should turn out to be identical.

I use xrecode for transcoding, it's more convenient than foobar, especially if you are converting a lot of files.
Unregistered shareware version has all features, it just have a nag box.