####################
Notes for PulseAudio
####################

There is way too much magic that simply isn't documented about this system.

Multiple Outputs
################

One of my computers has a graphics card that can drive multiple HDMI channels,
including their sound channels.  In order to be able to simultaneously route
audio out multiple channels (e.g., to two different monitors), I had to fiddle
deeper in the system than I would have liked.

First, I created a custom PulseAudio "profile",
``/usr/share/pulseaudio/alsa-mixer/profile-sets/nwf-multi-hdmi.conf``.  This
consists of a number of "Mappings" stanzas and a "Profile" stanza::

  [General]
  auto-profiles = no
  
  [Mapping hdmi-surround71]
  description = Digital Surround 7.1 (HDMI)
  device-strings = hdmi:%f
  paths-output = hdmi-output-0
  channel-map = front-left,front-right,rear-left,rear-right,front-center,lfe,side-left,side-right
  priority = 8
  direction = output
  exact-channels = no
  
  [Mapping hdmi-surround71-extra1]
  description = Digital Surround 7.1 (HDMI 2)
  device-strings = hdmi:%f,1
  paths-output = hdmi-output-1
  channel-map = front-left,front-right,rear-left,rear-right,front-center,lfe,side-left,side-right
  priority = 6
  direction = output
  exact-channels = no
  
  [Mapping hdmi-surround71-extra2]
  description = Digital Surround 7.1 (HDMI 3)
  device-strings = hdmi:%f,2
  paths-output = hdmi-output-2
  channel-map = front-left,front-right,rear-left,rear-right,front-center,lfe,side-left,side-right
  priority = 6
  direction = output
  exact-channels = no
  
  [Mapping hdmi-surround71-extra3]
  description = Digital Surround 7.1 (HDMI 4)
  device-strings = hdmi:%f,3
  paths-output = hdmi-output-3
  channel-map = front-left,front-right,rear-left,rear-right,front-center,lfe,side-left,side-right
  priority = 6
  direction = output
  exact-channels = no
  
  # Stitch together the mappings to make a profile
  
  [Profile nwf-multi-hdmi]
  description = NWF Multi HDMI
  output-mappings = hdmi-surround71 hdmi-surround71-extra1 hdmi-surround71-extra2 hdmi-surround71-extra3
  priority=1

Then, to tell PulseAudio to actually use this profile, a *udev* rule is
required::

    SUBSYSTEM=="sound" SUBSYSTEMS=="pci" KERNEL=="card*" ATTRS{vendor}=="0x1002" ATTRS{device}=="0xaaf0" ACTION=="change" ENV{PULSE_PROFILE_SET}="nwf-multi-hdmi.conf"