So, I'm using a a52 plugin for DTS over spdif output. The thing is I have 4 speakers, plus SB. So I was looking for a way to mix that channel into front R and L. Alsa/pulse allows that mixture, but I can't quite figure out how the syntax for it is.

So far all I got is this, but it isn't working:

# This block gets the DTS output on spdif, it works just fine
pcm.a52 {
  @args [CARD]
  @args.CARD {
    type string 
  }
  type rate
  hint.description "DTS Digital 5.1 Output"
  slave {
    pcm {
      type a52
      bitrate 640
      channels 6
      card $CARD
    }
  rate 48000 #required somehow, otherwise nothing happens in PulseAudio
  }
}

# This is what I tried to do, but didn't work
pcm.51to41 {
  type route
  slave.pcm "a52:0";
  slave.channels 6;
  ttable {
    ttable.0.0 1
    ttable.1.1 1
    ttable.2.2 1
    ttable.3.3 1
    ttable.5.5 1
    ttable.4.0 0.5
    ttable.4.1 0.5
 }
}