If you go to the link I provided and look on the specifications tab you will see : -
Music - MP3, WMA, OGG, WAV/PCM/LPCM, AAC, FLAC, Dolby Digital, AIF/AIFF, MKA
Photo - JPEG, GIF, TIF/TIFF, BMP, PNG
Video -MPEG1/2/4, WMV9, AVI (MPEG4, Xvid, AVC), H.264, MKV, MOV (MPEG4, H.264),MTS, TP, TS
Playlist - PLS, M3U, WPL
Subtitle -SRT (UTF-8), SMI, SUB, ASS, SSA
Note:
- MPEG2/4, H.264, and WMV9 supports up to 1920x1080p 24fps, 1920x1080i 30fps, 1280x720p 60fps resolution
- An audio receiver is required for surround sound output. AAC/Dolby Digital decodes in 2 channel output only
- JPEG does not support CMYK or loss less.
- BMP supports uncompressed format only.
- TIF/TIFF supports single layer only
Edit: Just noticed you say you get 5.1 decoded - could be a probkem with the notes.
Does it have an optical out on the back - I can see it has space for one.