My 920 wouldn't play the m4a format music, but according to the official website, 920 should support the m4a format:
Music format
Codecs: MP3, AMR-WB, AMR-NB, WMA 10 Pro, WMA 9, AAC LC, AAC+/HEAAC, eAAC+/HEAACv2
Audio format: ASF, Wav, MP4, AAC, AMR, MP3, M4A, WMA, 3GP, 3G2
Nokia Lumia 920 - Nokia
Anybody else have the same problem?
Music format
Codecs: MP3, AMR-WB, AMR-NB, WMA 10 Pro, WMA 9, AAC LC, AAC+/HEAAC, eAAC+/HEAACv2
Audio format: ASF, Wav, MP4, AAC, AMR, MP3, M4A, WMA, 3GP, 3G2
Nokia Lumia 920 - Nokia
Anybody else have the same problem?