How to configure ALSA (No PulseAudio) with software mixing and multiple users?

[John Doh <shillshocked@xxxxxxxxx>]

I have been able to get multiseat working with ALSA only including software mixing and an equalizer. But it only works if both seats are logged in as the same user. I would like to share the audio among different users.

Here is my working config for ALSA that allows multi-seat single user (a double login) using Arch Linux:

defaults.pcm.rate_converter "samplerate_best"

ctl.equal {
 type equal;
}

pcm.plugequal {
  type equal;
  # Modify the line below if you do not
  # want to use sound card 0.
  #slave.pcm "plughw:0,0";
  #by default we want to play from more sources at time:
  slave.pcm "plug:dmix";
}
#pcm.equal {
  # If you do not want the equalizer to be your
  # default soundcard comment the following
  # line and uncomment the above line. (You can
  # choose it as the output device by addressing
  # it with specific apps,eg mpg123 -a equal 06.Back_In_Black.mp3)
pcm.!default {
  type plug;
  slave.pcm plugequal;
}

I read over various wikis, forum posts and faqs on how to configure ALSA. This was what I came up with, and it is currently not working:

defaults.pcm.rate_converter "samplerate_best"

pcm.ossmix {
    type dmix
    ipc_key 1024 # must be unique!
    ipc_key_add_uid false   # let multiple users share
    ipc_perm 0666           # IPC permissions for multi-user sharing (octal, default 0600)
    slave {
        pcm "hw:0,0"      # you cannot use a "plug" device here, darn.
        period_time 0
        period_size 1024 # must be power of 2
        buffer_size 8192  # dito. It
       #format "S32_LE"
       #periods 128 # dito.
       #rate 8000 # with rate 8000 you *will* hear,
       # if ossmix is used :)
    }
    # bindings are cool. This says, that only the first
    # two channels are to be used by dmix, which is
    # enough for (most) oss apps and also lets
    # multichannel chips work much faster:
    bindings {
        0 0 # from 0 => to 0
        1 1 # from 1 => to 1
    }
}
pcm.dsp0 {
    type plug
    slave.pcm "ossmix" # use our new PCM here
}
# mixer0 like above
ctl.mixer0 {
    type hw
    card 0
}

# You may want to make your new ossmix the default for alsa.
# If your alsa programs are complaining that they can't open
# your sound devices, try uncommenting this next line
#pcm.default pcm.dsp0

What am I missing here?

------------------------------------------------------------------------------
Android apps run on BlackBerry 10
Introducing the new BlackBerry 10.2.1 Runtime for Android apps.
Now with support for Jelly Bean, Bluetooth, Mapview and more.
Get your Android app in front of a whole new audience.  Start now.
http://pubads.g.doubleclick.net/gampad/clk?id=124407151&iu=/4140/ostg.clktrk

_______________________________________________
Alsa-user mailing list
Alsa-user@xxxxxxxxxxxxxxxxxxxxx
https://lists.sourceforge.net/lists/listinfo/alsa-user