Re: Idea on volume adjusting

[Mike Kazantsev]

On Tue, 31 Jan 2023 23:29:55 +0100 (CET)
funk443--- via <emms-help@gnu.org> wrote:

> Currently volume adjustment of EMMS can only adjust master volume,
> which will bring some inconvenience while someone was trying to have
> some music via EMMS in the background while doing other stuffs that
> also plays sound (e.g. playing games, talking to others...).

> So I wrote some functions to adjust the volume of MPV player only,
> and please correct me if I am doing something wrong.

i think "volume" in mpv normally works this way:

- It is a "software volume", i.e. changes values of the samples sent to
  an audio API like PulseAudio or Pipewire.

- Starts at 100, meaning no boost or reduction.

- Going lower than 100 works mostly as expected - reduces volume in a
  sensible fashion.

- But going above 100 makes audio samples already close to max value
  all "smush together" which I think is usually called "clipping" in
  audio - information about actual sound gets lost.

Last part is something you might want to always avoid for stuff like
music, so this way of setting the volume is kinda limiting - allows to
adjust volume down, but not up without sound quality loss.

But modern audio APIs on linux also support per-application volumes,
which don't have such issues, as volume there doesn't start at 100%.
(and "100%" tends to mean "max possible volume from audio card",
which rarely needs to be that high)

You can also control that volume instead via "ao-volume" parameter,
which would allow raising volume without any quality loss and in way
where it's not hidden within mpv process, but that you can also control
from OS/DE-level mixer apps (e.g. pavucontrol that comes with pulse,
or its pipewire counterpart).

So thought to mention it as a potentially better alternative parameter
to tweak, if mpv makes "ao-volume" property available (i.e. knows how
to control current audio output's volume).

Though of course it might depend on the specific environment and setup.
"volume" should be more universal, even if a bit limited like that.


-- 
Mike Kazantsev // fraggod.net