Sorry for my English

I hope someone have an idea.

Equipment:
TV: Panasonic TX-49CXW754
BluRay Player: Panasonic DMP BDT700
AV Receiver: Pioneer SC-LX59K

What works:
BluRay DVD 3D works perfectly (eg: Jupiter Ascending).
I can watch 2D MKV movies on Usb Stick on BD Player.
I can watch 3D MKV movies on Usb Stick on TV (Selection: "Side-By-Side ==> 3D", but without DTS, which the TV doesn't support. I have to convert each movie to Dolby.


What didn't work and this is incredible annoying:
I can't watch any 3D MKV on this BD Player!
I see the Side-by-Side picture but the player don't switch in to 3D Mode.
The 3D settings of the player offer just: “Original”, “Side-by-Side” and “2D ==> 3D”.
On the TV I don't have anymore available “SBS ==> 3D”. It is greyed out, disbaled.

If I watch the same 3D MKV movie direct on the TV (without sound, 'cause of not supporting DTS), I DO have the option of “SBS ==> 3D” and it works like it supposed to do.
If I connect the player direct at the TV without AV Receiver I get the same results (no 3D with MKV).

The HDMI connectors seems correct (and they are new), 'cause I can see any normal BD 3D with the player. I can't find any settings on the player which offer SBS to 3D conversion.

It look like the BD player cut off some 3D Information when it sends the signals to the TV. (??)

Any one have any ideas ?

Is there a way to convert Back 3D MKV to real 3D?

Any hint s are highly appreciated!
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Regarding to this Thread <https://forum.videohelp.com/threads/343602-Best-Blu-Ray-Player-to-play-3D-MKV-%28DTS-audio%29-files-off-my-USB-HDD>, does this mean better not bother around with BD Player, better use a Media Player even it's a Rasberry Pi?