Hi, just wanted to share this tip about getting M4A format music from iTunes to play on a VW head unit.

I have a bog-standard RCD-310 in my 2011 Polo, and an MDI input in the glovebox. The audio manual clearly states that the RCD-310 can play AAC encoded music. A lot of people are aware that M4A format actually does contain AAC encoded music, as you've probably seen on the web and in Apple's own literature.

So, you've probably tried copying the M4A files onto a USB stick and then expected them to play - I mean, that would just be too easy right? Instead you find they don't work - you'll get "File Error" or some-such. However, MP3 files will play OK.

One solution would be to convert the M4A files to MP3 - but that's not a good solution because it's a conversion that will lose some quality of the original.

The good news is, you can make the M4A files play without re-encoding them to MP3. The problem why the RCD-310 (and presumably other head units) don't play the M4A files is because they contain extra bits and bobs which the head units can't handle in the same way a PC or Mac can.

Just to say at this point, M4A files do NOT have the DRM protection on them -- so this is not the reason they don't play (however, older M4P files definitely ARE protected by DRM. You will not be able to play these unless they are loaded on to an iPod).

So, here is a potential solution. Download the free audio/video conversion tool called FFMpeg from here: Get FFmpeg - it's available on Windows, Mac and Linux.

Then, you will need to open a Command Prompt (in Windows) and Terminal (in Mac or Linux) and type the following on the command-line. In this example, the file you are converting is called "song.m4a". The file it spits out will be called "song.aac" - what the command is doing is stripping out the rubbish inside the M4A file which is upsetting the head unit.

ffmpeg -i song.m4a -acodec copy song.aac

For those not confident of using the command-line, there are methods of using a GUI to run this command. Also, if you want to convert 1,000 songs then you will need a batch file. There are other guides on the Internet for this.

Anyway, I hope this helps someone. It worked for me on my RCD-310 on my Polo. I can't offer any advice for other cars or head units.