Sound goes out as Surround 5.1 over the HDMI cable on an Nvidia GT 630.

Volume amplification is at minimum 0dB - if I increase it, the screen freezes.

lspci:
01:00.0 VGA compatible controller: NVIDIA Corporation GK208 [GeForce GT 630
Rev. 2] (rev a1)
01:00.1 Audio device: NVIDIA Corporation GK208 HDMI/DP Audio Controller (rev
a1)

Kubuntu 16.04.1 with self compiled standard kernel 4.8.6
kodi version 15.2

Xorg.0.log says: 
[     4.645] (II) Module nouveau: vendor="X.Org Foundation"
[     4.645]    compiled for 1.18.1, module version = 1.0.12

kern.log:
Nov  9 13:18:51 s5 kernel: [  599.178480] nouveau 0000:01:00.0: fifo: PBDMA0:
00040000 [PBENTRY] ch 8 [003f902000 kodi.bin[2449]] subc 0 mthd 0000 data
00000000
Nov  9 13:18:51 s5 kernel: [  599.178502] nouveau 0000:01:00.0: fifo: PBDMA0:
00040000 [PBENTRY] ch 8 [003f902000 kodi.bin[2449]] subc 0 mthd 0000 data
00000000
Nov  9 13:18:51 s5 kernel: [  599.178515] nouveau 0000:01:00.0: gr: DATA_ERROR
0000000c [INVALID_BITFIELD] ch 8 [003f902000 kodi.bin[2449]] subc 0 class a197
mthd 114c data 05000000
Nov  9 13:18:51 s5 kernel: [  599.178522] nouveau 0000:01:00.0: fifo: PBDMA0:
00040000 [PBENTRY] ch 8 [003f902000 kodi.bin[2449]] subc 0 mthd 0000 data
00000000
Nov  9 13:18:51 s5 kernel: [  599.178533] nouveau 0000:01:00.0: gr: DATA_ERROR
00000003 [INVALID_OPERATION] ch 8 [003f902000 kodi.bin[2449]] subc 0 class a197
mthd 1158 data 3f800000
Nov  9 13:18:51 s5 kernel: [  599.178540] nouveau 0000:01:00.0: fifo: PBDMA0:
00040000 [PBENTRY] ch 8 [003f902000 kodi.bin[2449]] subc 0 mthd 0000 data
00000000