MP4 (Source is 5.1) playback is only 2ch

[Henke]

I only get 2 channel output when i play MP4

It happens no matter what source, but i specify the source file audio information from last MP4 playback when i experienced this:
Stream Audio Size...........: 265 MB (12%)
Audio/Bit Rate...............: AAC LC/320 Kbps
Channel(s)/Sampling Rate..: 6 channels/48.0 KHz
Channel Positions............: Front: L C R, Side: L R, LFE

I'm using VLC over SPDIF. Amplifier is Yamaha RX-V450, from what i understand it should handle the signal.
Luckily not all files out there is MP4, but from time to time i stumble upon these files and always have the same 2ch problem.
I'm out of ideas to solutions and didn't find any solutions when i searched (hope I'm not blind, but honestly i didn't find anything that helped).

Would be very nice of you if you could help me :)

[Jean-Baptiste Kempf]

Please share the logs.

[VLC_help]

You cannot pass AAC audio via SPDIF. Only AC3 and DTS audio are supported in SPDIF. And VLC doesn't have Dolby Live or DTS Connect support.