DVB-T TV: blank video, change gpu_mem, now coloured squares

I installed Kodi and TVHeadend.

Using:
Pi 3
Kodi 15
Raspian jessy
DVB-T
MPG2-License

My Problem is, that i got sound but no video. I changed the GPU-size in raspbian an now i got a picture of the stream for only a second an after that i got coloured squares like in the picture below.

watch gallery

Other videos from SD-card are playing correct.
I also tried TVHeadend from an other pc and it worked fine.