On Firefox, muting one tab mutes them all

[hishamhm]

Using Firefox 52 with apulse 0.1.9 and the dmix ALSA 1.1.3 plugin, Firefox can play audio from multiple tabs simultaneously and it works great.

When playing audio in multiple tabs, each tab gets a mute button. With direct ALSA+dmix in Firefox 51, this worked well, and tabs could be muted individually. With apulse, however, pressing "mute" on one tab is muting them all.

When I disable dmix, Firefox+apulse can't play multiple tabs simultaneously, so mixing is happening at ALSA level, so I assume apulse is sending separate streams for each tab via ALSA. I note also that the device does not get muted, so I believe apulse is muting "via software" (ie, not sending a mute command to the actual device).

This is my ~/.asoundrc to get software mixing via dmix working (but I have no reason to assume the same issue isn't happening with cards that do hardware mixing)

pcm.!default {
   type plug
   slave.pcm "dmix"
}
pcm.dmix  {
    type dmix
    ipc_key 1024
    slave {
      pcm "hw:0,0"
      period_time 0
      period_size 1024
      buffer_size 8192
   }
   bindings {
      0 0
      1 1
   }
}
ctl.dmix {
   type hw
   card 0
}
ctl.!default {
   type hw
   card 0
}

Thank you for apulse, it has become an essential tool in my system!

[hishamhm]

Decided to give it a shot at fixing this! I sent a PR that seems to work well. Thank you for a clear codebase, it was easy to find my way around the code. :)

[i-rinat]

Oops. I assumed volumes are per-context rather that per-stream. And while code was written, I was thinking about how strange it's that application has to make own volume scaling.

Thank you for fixing this.

[hishamhm]

Yay, thank you for reviewing quickly! Can't wait to get the next release merged in GoboLinux. :)