codec hint for MediaSource ( QIODevice * ioDevice )

My application processes encrypted mp3 files.
The files are decrypted in memory and passed as a QBuffer to MediaSource(QIODevice * ioDevice)
That works most of the time, however some specific mp3 files causes the Phonon DS backend to select the wrong codec.
Saving the decrypted content to a file named "xyz.mp3" and opening that using MediaSource ( const QString & fileName ) works, but that is not an acceptable option.

Is there a way to pass a format/codec hint to the DS backend?