[Audio] - Hardware volume keys are occasionally unable to mute an output device.

[ZereoX]

Your system information

• Steam client version (build number or date): 1731433018 (Stable) / 1730253536 (Beta)
• Distribution (e.g. Ubuntu): SteamOS 3.6.20 / 3.7.0 (Deck) and Manjaro w/ Gnome 46 (Desktop)
• Opted into Steam client beta?: Issue is present on both Stable and Beta
• Have you checked for system updates?: Yes
• Steam Logs: steam-logs.tar.gz
• GPU: AMD Van Gogh RDNA 2.0 (Steam Deck) and RX 7800XT (Desktop)

Please describe your issue in as much detail as possible:

Hardware volume keys, such as the - and + on the Steam Deck or the ones on an external Bluetooth keyboard, can occasionally be unable to mute an output devices. Volume keys have less granularity when compared to volume sliders (0.05 Vs. 0.01 steps of control). This can cause the volume to remain stuck between 0.01 and 0.04 if the volume was adjusted via a slider (i.e. not a multiple of 0.05) and then lowered via a hardware key.

Video

https://github.com/user-attachments/assets/ba9386b7-e70b-463c-bcb1-9189b6b53af2

Steps for reproducing this issue:

1. Turn the Steam Deck Speaker volume all the way down.
2. Under Steam > Settings > Audio or Quick-Access Menu > Quick Settings > Audio, use right on the d-pad to increase the Output Device volume by one step.
3. Attempt to turn the volume back down using the - key.

Reproduction Rate: 5/5.

Affected Platforms

• LCD / Jupiter: Yes, Gaming Mode only
• OLED / Galileo: Yes, Gaming Mode only
• Desktop Deck-like session (gamescope -e -- steam -gamepadui -steamdeck): No
• Desktop: No

Note: In Big Picture Mode hardware keys are always able to fully mute a device.

Actual result

• Volume keys are unable to fully mute a device if the current volume is not a multiple of 0.05.

Expected result

• Volume keys can always mute a device regardless of their current volume level.

Notes

• This issue can be fixed by using one of the various volume sliders, but for the volume key to be able to resolve this, the volume must be increased to the maximum (1.00) and then lowered all the way back down.
• Current sink volume levels can be checked via wpctl status.