Dual audio using asound.conf

# asound.conf for Dual Audio - SPDIF (5.1) + HDMI Stereo out
# by puntloos

pcm.!default {
        type plug
        slave {
                pcm "both_digital"
        }
}

# First we create a 'both' route, that has 12 channels
pcm.both_digital {
        type route
        slave {
                pcm multi
                channels 12
        }
        # And we route the channels 1:1
        # 6 inputs (0-5) get mapped into 12 outputs (0-11)
        # (this is how we copy channels)
        ttable.0.0 1.0
        ttable.1.1 1.0
        ttable.2.2 1.0
        ttable.3.3 1.0
        ttable.4.4 1.0
        ttable.5.5 1.0
        ttable.0.6 1.0
        ttable.1.7 1.0
        ttable.2.8 1.0
        ttable.3.9 1.0
        ttable.4.10 1.0
        ttable.5.11 1.0
}

# Then define a multi device that splits the 12-channel input
# Into 2x 6 output

pcm.multi {
        type multi
        slaves.a {
                pcm "spdif_out"
                channels 6
        }
        slaves.b {
                # virtual hdmi still has 6 channels
                # although I suppose I could try making it 2
                pcm "hdmi_virtual"
                channels 6
        }

    # Bind stuff to the SPDIF outputs
        bindings.0.slave a
        bindings.0.channel 0
        bindings.1.slave a
        bindings.1.channel 1
        bindings.2.slave a
        bindings.2.channel 2
        bindings.3.slave a
        bindings.3.channel 3
        bindings.4.slave a
        bindings.4.channel 4
        bindings.5.slave a
        bindings.5.channel 5

        # And to the HDMI outputs
        bindings.6.slave b
        bindings.6.channel 0
        bindings.7.slave b
        bindings.7.channel 1
        bindings.8.slave b
        bindings.8.channel 2
        bindings.9.slave b
        bindings.9.channel 3
        bindings.10.slave b
        bindings.10.channel 4
        bindings.11.slave b
        bindings.11.channel 5
}

# Since hdmi is 2 channels, we downmix.
pcm.hdmi_virtual
{
  type route
  slave.pcm hdmi_out
  slave.channels 2

  # Front and rear, at 33% of original signal strength
  ttable.0.0 0.33
  ttable.1.1 0.33
  ttable.2.0 0.33
  ttable.3.1 0.33

  # Center channel routing (routed to front-left and front-right),
  # 6dB gaindrop (gain half of main channels) per channel
  ttable.4.0 0.16
  ttable.4.1 0.16

  # LFE channel routing (routed to front-left and front-right),
  # 6dB gaindrop (gain half of main channels) per channel
  ttable.5.0 0.16
  ttable.5.1 0.16
}

# And here is my actual hardware
# Note that this is linked to the output of 'aplay -l'
# HDMI output
pcm.spdif_out {
        type hw
        card 0
        device 1
        channels 6
}

# Stereo output
pcm.hdmi_out {
        type hw
        card 1
        device 7
        channels 2
}