RPI3 + HifiBerry / HiFiDigi passtrought 5.1 ???

Hi All!

I used my RPI 3 (Libreelec 7.0.2) with an HiFiDigi+ SPDIF soundcard which is a HifiBerry replication. I used it with my Samsung HW-F355 2.1 Soundbar.
It worked perfect. But now i bought a Samsung HW-K550 + Rearkit soundbar, which is an 5.1 sound system.

I changed my audio settings in kodi to 5.1, 5.1 passtrough, and etc. But it didn't work right. I downloaded some 5.1 channel test video, and i always hear the same. When i must hear just the front right, i hear front and rear right, when i must hear the front left i hear front and rear left... and when i must hear subwoffer in the channel test... there isn't any sound....:(

Is someone who tell me what could i do to wokrking the 5.1 with HifiBerry? Or am i misunderstanding, and HifiBerry doesn't have ability to 5.1 sound, or 5.1 passtrough??

A cheked another option: RPI3 (Soundcard HDMI 5.1)--> HDMI cable-- > Samsung HW-K550 --> HDMI cable (ARC) - Samsung TV
But it was the same, i didn't get any true 5.1 sound, when i play the channel test videos.

In SSH i get this:
LibreELEC (official) Version: 7.0.2
TOTI-RPI:~ # speaker-test -D plughw:0,0 -c2

speaker-test 1.1.1

Playback device is plughw:0,0
Stream parameters are 48000Hz, S16_LE, 2 channels
Using 16 octaves of pink noise
Rate set to 48000Hz (requested 48000Hz)
Buffer size range from 16 to 131072
Period size range from 8 to 65536
Using max buffer size 131072
Periods = 4
was set period_size = 32768
was set buffer_size = 131072
0 - Front Left
1 - Front Right
Time per period = 2.757435

TOTI-RPI:~ # speaker-test -D plughw:0,0 -c6

speaker-test 1.1.1

Playback device is plughw:0,0
Stream parameters are 48000Hz, S16_LE, 6 channels
Using 16 octaves of pink noise
Rate set to 48000Hz (requested 48000Hz)
Buffer size range from 16 to 131072
Period size range from 8 to 65536
Using max buffer size 131072
Periods = 4
Unable to set hw params for playback: Invalid argument
Setting of hwparams failed: Invalid argument
TOTI-RPI:~ # aplay -L
null
Discard all samples (playback) or generate zero samples (capture)
default:CARD=sndrpihifiberry
snd_rpi_hifiberry_digi,
Default Audio Device
sysdefault:CARD=sndrpihifiberry
snd_rpi_hifiberry_digi,
Default Audio Device

Is someone have some ide, what could i do?

Thanks Best Regards.....

Quote from popcornmix

Don't do that. Number of channels *must* be set to 2.0 when using spdif/toslink.
Number of channles is only used for multichannel PCM, which is a HDMI feature.
Passthrough will still work with number of channels set to 2.0.

Thanks for your answer. Now i realise, my downloaded video was Dolby Digital Plus, and my soundbar is only working with Dolby Digital.
So if i set RPI3 --> HDMI (5.1, passtrough, ac3 /Dolbi Digital/) --> Soundbar --> TV and i downloaded free soround music from this site: Free surround music download - 5.1 Dolby Digital "5.1 Surround Test File" and i hear the channels sound in the right places. Front Left --> Font Left.. etc. So the HDMI 5.1 is working now. DONE.

But the spdif... So i missed some details in my first post. In my Libreelec / Kodi settings i couldn't set the channel numbers when is use spdif (HifiDigi+).
I could set if i want to passtrough or not. So is that you said is meaning, i can't passtrough 5.1 channel sound in spdif ?? Or i still don't understand, the whole things? Because i hear the sound with this version: (Sound connection): RPI3 --> Spdif(HifDigi+, passtrough, without ace3 /if i set this option, there is no sound/) --> Soundbar, (Video connection): RPI3 --> HDMI --> TV . But this version i just hear 2.0 sound on my 6 speaker.

Spdif = 2.0 ?