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Make effect volume slider non-linear #8950

merged 2 commits into from Apr 6, 2021


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@PeterN PeterN commented Apr 5, 2021

Motivation / Problem

The effect volume slider has barely any effect on perceived volume until down into the low values.


This is because perceived audio loudness is non-linear, but our code treats it as such,

This is approximately documented here:

This change introduces x^3 scaling rather than the suggested x^4 or x^5 scaling, as this "feels" fine and whereas the latter curves seem excessive. This is just a game, not professional audio mixing software, after all. It also feels similar to how the music volume slider already works, at least for the soft-synth on Windows.

And additional change to increase the permitted sample range values to avoid clipping is included, but the volume slider change doesn't have any bearing on that.


Existing volume adjustment will probably be too quiet now, however the level can easily be adjusted up.

Checklist for review

Some things are not automated, and forgotten often. This list is a reminder for the reviewers.

  • The bug fix is important enough to be backported? (label: 'backport requested')
  • This PR affects the save game format? (label 'savegame upgrade')
  • This PR affects the GS/AI API? (label 'needs review: Script API')
    • ai_changelog.hpp, gs_changelog.hpp need updating.
    • The compatibility wrappers (compat_*.nut) need updating.
  • This PR affects the NewGRF API? (label 'needs review: NewGRF')
PeterN added 2 commits Apr 5, 2021
Clamping each sample value to half the available range could cause
unnecessary premature clipping with lots of sounds playing. This change
does not affect the actual volume level.
LordAro approved these changes Apr 6, 2021
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@LordAro LordAro left a comment


@LordAro LordAro merged commit 920bf70 into OpenTTD:master Apr 6, 2021
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@PeterN PeterN deleted the non-linear-volume branch Apr 6, 2021
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3 participants