You plug the HDMI, the video works but you have no audio. Ok, go on.
PulseAudio is a sound system for POSIX OSes, meaning that it is a proxy for your sound applications. It allows you to do advanced operations on your sound data as it passes between your application and your hardware. Things like transferring the audio to a different machine, changing the sample format or channel count and mixing several sounds into one are easily achieved using a sound server. PulseAudio is an integral part of all relevant modern Linux distributions and used in various mobile devices by multiple vendors. PulseAudio is an integral part of all relevant modern Linux distributions and used in various mobile devices by multiple vendors.
List name or index number of possible sinks:
you should see a “*” near the index of the sink actually in use.
If you see only one sink you are in trouble, the system doesn’t recognize the device. Search away!
Otherwise connect the HDMI, take an mp3 and try:
pacmd set-default-sink sinkIndex pulseaudio -k pacmd set-default-sink -D
varying the value of sinkIndex using the values found with pacmd list-sinks but be careful to close the program that you use to play the mp3.