Depending on your sound hardware you may also find the appropriate port to where your digital HDMI sound goes. To list ports of cards available issue:
pacmd list-cards
Usually there are several profiles available to adress different ports. These will also be lsited with the command above. Try if selecting another profile gives you the expected results (replace <card-index>
and <profile-name>
with values read above):
pacmd set-card-profile <card-index> <profile-name>
If no profiles adressing different ports are available you can also change the port of a given sink with:
pacmd list-sinks # to read the sink index for the next command
pcmad set-sink-port <sink-index> <port-name>
In case you have a graphical desktop you may also change the card profile with pavucontrol in the "Configuration" tab:
Note that different HDMI-profiles may be listed which all show up having the same name.
If all that fails you may try to disable HDMI-CEC on your TV set or try with a different HDMI cable as flickering of the screen on your TV set may indicate an erroneous electrical input on the HDMI-ports.