I noticed that some video files, such as movies, have barely audible spoken words in them. The sound effects, the background music, all that is fine. But when the actors speak, they are inaudible.
This happens because the audio in these files is recorded in multi-channel mode (5.1 or 7.1) but my setup lacks the additional speakers for correct playback.
To fix this, we need to tell our audio playback software to mix down the audio into two channels only.
In VLC, select Audio > Stereo Mode > Stereo in the menu.
For MPV, start it up with the --audio-channels=stereo flag or set audio-channels=stereo in your ~/.config/mpv/mpv.conf file.
If the folder and file don’t exist, create them:
mkdir ~/.config/mpv
cd ~/.config/mpv/
touch mpv.conf
nano mpv.conf
In Celluloid, go to Preferences > Config Files > Load MPV config file. And load the above mentioned (or created) configuration file.