Sound with HDMI and optical in the same time

I've got wierd problem.

I've got i5 4690 processor and MSI Z97M-G43 motherboard. I'm using integrated GPU.

Monitor is connected with DVI and with HDMI I've got tv connected. Problem is that screen is flickering, but only when there is no sound on HDMI. But I want to use my sound system (optical wire) as default sound.

I'm using Kodi (XBMC). Can I set that sound will be sent with HDMI and optical cable in the same time?