I had my device up to date. A m4a file was created by the famous nero encoder and transferred to my device via Ovi suite (using the sync button). However, the phone can't find the file in the music library. Strangely, the file can be chosen as the ringtone and it plays fine.
The nero encoder uses HE-ACC v2 standard, that is, eaac+, which is supported by N97 mini.
Can anyone shed some light on this? Thanks.