Ok, I enabled the m4a plugin in gtkpod. Now, when I try to add the directory with the m4a files to the gtkpod Music Library, gtkpod crashes immediately. Here are the error messages:

*** buffer overflow detected ***: gtkpod - terminated
gtkpod: buffer overflow attack in function <unknown> - terminated


On Mon, Jul 30, 2012 at 8:50 AM, Tim Cuthbertson <ratcheer@gmail.com> wrote:
Thank you. I will look for the plugin.

To import m4a files you need the m4a filetype plugin installed and enabled. Depending on how you installed gtkpod, this plugin may have not been installed.