Knowledge Base

I have a Ubuntu 16.04 instance (I'm not proud) because at the time, Kodi only supported 16.04 of the Ubuntu family and I didn't feel like compiling it myself on another platform, or depending on prebuilt binaries (if that's even an option). I ended up not really liking the 10-foot interface that Kodi had to offer (as well as it seemed to really stink at populating its indices of my own local content!), and I really like the paradigm of a desktop environment with traditional file manager and media player programs. So I will reimage the system with Devuan at some point, but that's another day's problem. One of the little issues that I have discovered somehow between PulseAudio and HDMI is that upon each boot, the default audio out is the built-in speakers in the computer case. I have to manually adjust pavucontrol to set it to be the HDMI out audio that sends it to the big screen. I decided to automate this so others don't have to know what option to select on what tab in what program, in order to get the sound to goto the TV. I remember (fondly, actually) my automation days in obsolete, proprietary OSes using AutoHotKey. A great way to simulate key presses in X11 (because Wayland seems as scary as systemd or pulseaudio) is to use xdotool (which I've written about before). Using my tried-and-true desktop-file-calls-shell-script method, I have whipped up a nice desktop icon for the user to call after first logging in.

[Desktop Entry]
Name=Output audio to HDMI
Exec=/home/kodi/bin/set-sound.sh
Type=Application
StartupNotify=true
Path=/home/kodi
Icon=multimedia-volume-control
StartupWMClass=pavucontrol
Terminal=true
Comment=Configures pulseaudio to send audio to HDMI automatically

And the shell script:

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#!/bin/sh -x
# goal: set sound to have audio output to HDMI for the television.
# startdate: 2019-08-01 22:09
# dependencies:
#    pavucontrol
#    xdotool

pavucontrol &
sleep .5
xdotool key --delay 25 alt+c Down alt+Down End Up Up Up Return
# Return
# 3 up buttons to select the option fourth from the bottom in the list.
# this is very hard-coded for the kodi machine in the living room.

The hard part of course was finding how to notate the different keystrokes very precisely, with the capitalization and special characters.

Auxiliary info and asides

Pro tip: Don't ever configure "Alt+F4" in an xdotool script, especially when you load it up into ~/.config/autostart, and not bound to a specific window class. I really messed up the Xfce session almost permanently because I magically closed out xfwm, xfdesktop, and I think even xfpanel. That was embarrassing, big-time. Took me a while to even figure out what I had done. I couldn't figure out how to use the "search" window stack population function of xdotool, to identify the pavucontrol window, so I couldn't restrict my simulated keypresses to just pavucontrol. I also learned later that when the terminal window running the shell script is terminated, it kills even the backgrounded job of pavucontrol, so no ALT+F4 was required.