I just installed Debian 8 on a new ASUS z87-a and most things work fine right out of the box. However even though DVI and regular sound output work fine, I tried the HDMI connection but I have no sound and the image is just a blue screen. I tried also the sound optical output and got no sound either. Is there some special drivers that need to be installed for HDMI and SPDIF to work?

not sure I understand what I have to do

parents@pc8:~$ aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: HDMI [HDA Intel HDMI], device 3: HDMI 0 [HDMI 0]
Subdevices: 1/1
Subdevices #0: subdevice #0
card 0: HDMI [HDA Intel HDMI], device 7: HDMI 0 [HDMI 1]
Subdevices: 1/1
Subdevices #0: subdevice #0
card 1: PCH [HDA Intel PCH], device 0: ALC892 Analog [ALC892 Analog]
Subdevices: 1/1
Subdevices #0: subdevice #0
card 1: PCH [HDA Intel PCH], device 1: ALC892 Analog [ALC892 Digital]
Subdevices: 1/1
Subdevices #0: subdevice #0

I am a beginner in Linux... what exactly do I have to do to make work HDMI and optical output for sound?

You obviously have 2 hdmi ports, there are 2 listed. Choose 1 either {card0 device3} or {card 0device 7}. Did you see my .asoundrc file? Copy & edit it. it goes in your home directory.

I tried all possible combinations but didn't work. However when I checked with aplay -L (capital "L") I noticed that the optical output was listed

iec958:CARD=PCH,DEV=0
HDA Intel PCH, ALC892 Digital
IEC958 (S/PDIF) Digital Audio Output

this was the only place where I found S/PDIF referrred to.. I would prefer to use this optical output but how to do it? any new ideas?

HERE IS A COMPLETE LIST of devices from aplay -L command

root@pc8:~# aplay -L
No protocol specified
xcb_connection_has_error() returned true
No protocol specified
xcb_connection_has_error() returned true
null
Discard all samples (playback) or generate zero samples (capture)
pulse
PulseAudio Sound Server
hdmi:CARD=HDMI,DEV=0
HDA Intel HDMI, HDMI 0
HDMI Audio Output
hdmi:CARD=HDMI,DEV=1
HDA Intel HDMI, HDMI 1
HDMI Audio Output
dmix:CARD=HDMI,DEV=3
HDA Intel HDMI, HDMI 0
Direct sample mixing device
dmix:CARD=HDMI,DEV=7
HDA Intel HDMI, HDMI 1
Direct sample mixing device
dsnoop:CARD=HDMI,DEV=3
HDA Intel HDMI, HDMI 0
Direct sample snooping device
dsnoop:CARD=HDMI,DEV=7
HDA Intel HDMI, HDMI 1
Direct sample snooping device
hw:CARD=HDMI,DEV=3
HDA Intel HDMI, HDMI 0
Direct hardware device without any conversions
hw:CARD=HDMI,DEV=7
HDA Intel HDMI, HDMI 1
Direct hardware device without any conversions
plughw:CARD=HDMI,DEV=3
HDA Intel HDMI, HDMI 0
Hardware device with all software conversions
plughw:CARD=HDMI,DEV=7
HDA Intel HDMI, HDMI 1
Hardware device with all software conversions
default:CARD=PCH
HDA Intel PCH, ALC892 Analog
Default Audio Device
sysdefault:CARD=PCH
HDA Intel PCH, ALC892 Analog
Default Audio Device
front:CARD=PCH,DEV=0
HDA Intel PCH, ALC892 Analog
Front speakers
surround21:CARD=PCH,DEV=0
HDA Intel PCH, ALC892 Analog
2.1 Surround output to Front and Subwoofer speakers
surround40:CARD=PCH,DEV=0
HDA Intel PCH, ALC892 Analog
4.0 Surround output to Front and Rear speakers
surround41:CARD=PCH,DEV=0
HDA Intel PCH, ALC892 Analog
4.1 Surround output to Front, Rear and Subwoofer speakers
surround50:CARD=PCH,DEV=0
HDA Intel PCH, ALC892 Analog
5.0 Surround output to Front, Center and Rear speakers
surround51:CARD=PCH,DEV=0
HDA Intel PCH, ALC892 Analog
5.1 Surround output to Front, Center, Rear and Subwoofer speakers
surround71:CARD=PCH,DEV=0
HDA Intel PCH, ALC892 Analog
7.1 Surround output to Front, Center, Side, Rear and Woofer speakers
iec958:CARD=PCH,DEV=0
HDA Intel PCH, ALC892 Digital
IEC958 (S/PDIF) Digital Audio Output
dmix:CARD=PCH,DEV=0
HDA Intel PCH, ALC892 Analog
Direct sample mixing device
dmix:CARD=PCH,DEV=1
HDA Intel PCH, ALC892 Digital
Direct sample mixing device
dsnoop:CARD=PCH,DEV=0
HDA Intel PCH, ALC892 Analog
Direct sample snooping device
dsnoop:CARD=PCH,DEV=1
HDA Intel PCH, ALC892 Digital
Direct sample snooping device
hw:CARD=PCH,DEV=0
HDA Intel PCH, ALC892 Analog
Direct hardware device without any conversions
hw:CARD=PCH,DEV=1
HDA Intel PCH, ALC892 Digital
Direct hardware device without any conversions
plughw:CARD=PCH,DEV=0
HDA Intel PCH, ALC892 Analog
Hardware device with all software conversions
plughw:CARD=PCH,DEV=1
HDA Intel PCH, ALC892 Digital
Hardware device with all software conversions

I thought you were working on hdmi
Spdif should be listed in Sound Settings, just select from there.

Weird thing... When I got back into Multimedia/Sound settings and fiddle a little bit it made optical sound then also later HDMI sound (also after the video worked in HDMI). I even deleted the .asoundrc file and it still works fine. Thanks for your help and time spent on this

Great glad you got it working.