PulseAudio 3.0 on Gentoo Linux.
After the output for a given stream is toggled, LFE remixing is always on, regardless of the value of the disable-lfe-remixing config file option.
Steps to reproduce:
enable-remixing = yes
disable-lfe-remixing = yes
default-sample-channels = 6
2) Have at least two outputs: one 5.1ch with LFE and one 2.0ch without. (note: in my case, the 5.1ch output is a remote PulseAudio server via tunnel, while the 2.0ch output is a local sound card. This probably doesn't matter).
3) play something with low-frequency content, such as (using SoX):
$ play -c 2 -n synth sine 60
This should default to the 5.1ch output (if it doesn't, toggle it, then restart the command and make sure it picked it by default)
4) unlock the channels on the 5.1ch output and move the subwoofer slider. Observe that there is no change in the output volume (in my case, the 60Hz plays through the other outputs, and is crossed over to the subwoofer by the speakers themselves, not PA)
5) toggle the stream to the 2.0ch output
6) toggle the stream back to the 5.1ch output. In my case, the tone now sounds ~10dB louder (because my LFE output is mixed in at +10dB, as is the standard)
7) move the subwoofer slider again. Observe that the output varies from the correct level (when the subwoofer output is muted) to ~+10dB, when it is at 100%, so the audio is being incorrectly remixed to the LFE channel.
It sounds like fixing this would probably be easy, so I'll add the "love" keyword to make this bug appear in the easy bugs list.
I believe this is already fixed with the following commit:
Could you please build PulseAudio from git and recheck?
I won't be able to test this for ~1 month (I don't currently have access to enough hardware to reproduce it - it's being transported). If anyone else can confirm that the commit fixes the issue, or if you're confident enough that it does, feel free to close.
I'm closing this, feel free to reopen if the issue is not gone.