Tvheadend

Hello all,

today I set up two Raspberry PI 2 with OSMC and TVheadend. One as the Streaming Server the other as a Client.
I am using a Sundtek MediaTV Pro III as tuner (DVB-C).

When I start to watch LiveTV on the OSMC Client, especially with HD Channels, the Stream starts to stutter and I see a lot of atifacts. Most of the time, the sound is 5 -10 seconds behind the picture....
I have the same situation if I start a Stream on my Windows PC (VLC).

Where can I start to search? Has someone faced the same problems?

Regards,
Lubi