Hi,
It appears Monkey Audio demuxer sets codec_tag to 'APE ' while official 
fourcc (which is looked for in probe()) is 'MAC '.
 >    st->codec->codec_type      = CODEC_TYPE_AUDIO;
 >    st->codec->codec_id        = CODEC_ID_APE;
 >    st->codec->codec_tag       = MKTAG('A', 'P', 'E', ' ');
Kostya, any reason you did this ?
Ben