pulseaudio-equalizer makes Firefox HTML5 players increase system volume

Summary

The volume controls in Firefox HTML5 players (YouTube for instance) are increasing (but not decreasing) the system volume if touched when pulseaudio-equalizer is enabled.

The volume for the whole application (named AudioIPC Server in sound settings) is also increased.

I have found volume issues for only Firefox, but this is clearly an issue related to pulseaudio-equalizer since this only happens when it is used for output and not when only the soundcard output is selected.

The same problem appears with other third-party developed equalizers, such as this: https://github.com/kernelOfTruth/pulseaudio-equalizer

System volume is also adjusted to the player volume upon page loading, sometimes to 100%.

It also adjusts the system volume when jumping around in the player.

Risks

This bug may cause both hardware damages and hearing damages. It also makes the equalizer unreliable together with Firefox.

Environment

Debian 9 Mate, Mozilla Firefox 60.6.1. System is updated daily. Note, there are 2 sound cards noted in files, only the external USB card is used. Also note that I have left out username and hostname names in the files.

aplay-l.txt

arecord-l.txt

pactl-info.txt

pactl-list.txt

pulseaudio-version.txt

uname-a.txt

Steps to reproduce

• Install latest version of Debian.
• Install Firefox ESR: sudo apt-get install firefox-esr.
• Install pulseaudio-equalizer: sudo apt-get install pulseaudio-equalizer.
• Get the sink name, take the relevant name within < and >: pacmd list-sinks | grep -e 'name:' -e 'index
• Set the default output sink: pacmd set-default-sink Enable dbus and equalizer modules: pacmd load-module module-equalizer-sink; pacmd load-module module-dbus-protocol
• Go to system sound settings and select the "FFT based equalizer on ".
• Run GUI: qpaeq & (maybe not needed)
• Warning! Protect your hardware and ears, assume you get 100% output below and choose test content accordingly and remove headphones from the head or turn down physical volume knobs.
• Run Firefox and go to a Youtube video - the volume level in the video player will be used for the system volume level.
• Increase the volume in the video player, the volume level is now reflected in system volume level.
• Jump around in the video player, the volume level in the player will be used again for system volume level.

What is the current bug behavior?

Firefox HTML5 player volume controls directly adjust/increase system volume when pulseaudio-equalizer is enabled.

What is the expected correct behavior?

Firefox HTML5 player volume controls should not increase system volume when changed - the same behavior as when the default sound card is selected and equalizer is not used.

Problem seems to be that with pulseaudio-equalizer enabled, then the Firefox volume changes "leaks" through to the system volume.