Video and audio not working

Hi, I am new in the *BSD world (even if I had used Debian for several years), so I say hello to everyone.

I have installed FreeBSD 11.0 on my laptop, but I cannot play neither audio nor video (local files or streaming): VLC just give me "oss audio output error", cmus does not work as well, even youtube videos does not start.

I think I just miss something stupid, but don't know what.

(sorry for my bad English, I am Italian)
Thank you for the answer,
now I can play video without audio and VLC give me no error, but just if i do # sysctl hw.snd.default_unit=0, else the situation is the same of the previous message.

# cat /dev/sndstat
Installed devices:
pcm0: <Intel Broadwell (HDMI/DP 8ch)> (play)
pcm1: <Realtek (0x0282) (Analog)> (play/rec) default
pcm2: <Realtek (0x0282) (Analog)> (play/rec)
No devices installed from userspace.

If I run # dmesg | grep pcm I have those messages for pcm1 and pcm2:
pcm1: chn_write(): pcm1:virtual:dsp1.vp0: play interrupt timeout, channel dead
pcm2: chn_write(): pcm2:virtual:dsp2.vp0: play interrupt timeout, channel dead

I think it is just a missing driver, isn't it?
It might be that you get better results with the new & not-yet-committed to an official release drm-next drivers. I'm using these since a few months on a laptop very successfully. They handle broadwell HDMI much better. The easiest way to test this is to install TrueOS and see how it goes - they have already bundled the drivers in.