Questions[idle](ubuntu)

I use an external monitor that has an audio output and use it for my audio system. However, if the desktop enters in sleep mode, it automatically switches to the laptop speakers.

I want to use pacmd list-sink-inputs | grep 'RUNNING' to check every 20 seconds if sound is playing, and if so reset the idle time automatically.

Currently I use caffeine, but that disables idling completely.

How can I prevent the computer going to sleep when sound is playing? How can I reset the idle time from the command line?

Clean installation of Ubuntu 18.10 beta

I want the screen to turn off after 1 minute of inactivity, but I do not want the system to be locked when it is activated again. So I do :

gsettings set org.gnome.desktop.session idle-delay 60
gsettings set org.gnome.desktop.screensaver lock-enabled false

The screen turns off after 1 minute of inactivity. The problem is that after that when I try to access the system it is stuck at a purple screen similar to the one of the lock screen but with no input form for password. The only way to access the system, is to suspend the system and then resume.

Do you have any view on this?

How can I set idle delay time on Ubuntu 18.04 suspend on terminal?

I'm using audio output over HDMI from my video card (Radeon HD-4650 RV730) to an AVR.

When there is no audio output it seems that the system turns off the audio and my receiver shows no audio input. Then, when audio starts, it takes a second or two for the signal to be recognized by my receiver, so I loose the start of the audio, or don't hear short sounds at all. I'd like to keep this connection "on" or "alive" even when no audio is playing so I don't have to wait for my receiver to switch over.

I believe this is an "idle" setting somewhere, but I'm not sure at what level it is happening. I'm a little fuzzy on how driver/pulseaudio/alsamixer all work together and at what level this can be solved. Rather than poking around and messing something up, I'd appreciate some guidance. Any explanations of commands would be greatly appreciated as I am new to Linux and trying to learn as much as I can.

When there are no users on my system, I would like the hard disk to spindown to low-power state. I realize that this might not be 100% achievable for a straight 24 hours, but it seems reasonable that the system could remain idle for a few hours at a time when it is not in use.

My system is headless and running a limited number of services. The primary services are: exim4, mythtv-backend, nfs, samba, cups, apt-cacher-ng

Assume that drives are already enabled to go into standby mode. Also, its not acceptable to increase the write-back timeout, since my system is not on a UPS.