[SMPlayer] How to downmix DD5.1 to stereo?

I’m currently running dualboot with Windows 10 and Manjaro Cinnamon. I noticed watching a video that it had normal sound level on Windows 10 (played in PotPlayer), but on Manjaro in SMPlayer (using mpv engine) the voices were low volume and music and “action” sounds were loud, too loud.

After some searching I found out that the cause must be the 5.1 sounds played on 2.0 device. On Windows and PotPlayer, downmixing is flawlessly achieved, audi level is normal throughout the video. However I can’t find a single setting in SMPlayer that allows me to downmix it to stereo. Or a working command setting for mpv that I can set inside SMPlayer in the mpv section.

How to set it?

It does it automatically for me. Check Audio > Channels while the video is playing. Also make sure under Options > Preferences > General > Audio that the Output driver and Channels by default are set to Default.

Ok, setting Audio > Channels to stereo does somewhat normalize the sound level, it’s not perfect, but better.

I made a comparison video of the sound levels: https://www.youtube.com/watch?v=zhmnvQ6FUPE

Vocal part is the “quieter” part while music is the “louder” part. Sound is recorded with Audacity on the same volume. Audio is from one video file, picked randomly a quiet and loud part.

As one can hear, compared to PotPlayer’s stereo output (which is by default, no settings needed), the output of SMPlayer after setting it to stereo channels is still much louder. Not mentioning the SMPlayer stock output, which is really loud.

If there is no other possible options to make it even better (and sound normalization is not one that I would use), I’ll have to live with this.