# using hdmi0 for TV stereo, hdmi1 for a 5.1 speaker set-up
# unfortunately, a non-square speaker number creates some noise
# therefore for hdmi1 we declare 8 speakers, but re-map them to 6 speakers 
pcm.hdmi0 {
  type hw
  card 0
}
pcm.hdmi1 {
  type route
  slave {
    pcm "hw:1,0"
    channels 8
  }
  ttable {
    0.0 = 1
    1.1 = 1
    2.2 = 1
    3.3 = 1
    4.4 = 1
    5.5 = 1
    6.0 = 0.5
    6.2 = 0.5
    7.1 = 0.5
    7.3 = 0.5
  }
}

# upmix stereo to 5.1 – so we can watch stereo YouTube on all speakers
# with this: $ chromium-browser --alsa-output-device=stereo51
# (numbers taken from <https://www.volkerschatz.com/noise/alsa.html>)   
pcm.stereo51  {
  type route
  slave {
    pcm "hw:1,0"
    channels 8
  }
  ttable {
    0.0 = 1
    0.2 = -0.6
    0.3 = -0.39
    0.4 = 0.5
    0.5 = 0.5
    1.1 = 1
    1.2 = -0.6
    1.3 = -0.39
    1.4 = 0.5
    1.5 = 0.5
  }
}

# default to hdmi0, overwrite with AUDIO_HDMI=1 env prefix
pcm.!default {
  type plug 
  slave.pcm {
    @func concat
    strings [
      "hdmi"
      {
        @func getenv
        vars [ AUDIO_HDMI ]
        default "0"
      }
    ]
  } 
}
ctl.!default {
  type hw 
  card {
    @func getenv
    vars [ AUDIO_HDMI ]
    default 0 
  }
}