pcm.!default {
    type plug
    slave.pcm multi
}

pcm.multi {
    type multi
    slaves {
        b { pcm "dmixer_a" channels 2 }
        a { pcm "dmixer_b" channels 2 }
    }

    bindings [
        { slave a channel 0 }
        { slave a channel 1 }
            { slave b channel 0 }
            { slave b channel 1 }
    ]
}

pcm.dmixer_b {
    type dmix
    ipc_key 2048
    slave {
        pcm "hw:1,0"
    }

    bindings {
        0 0
        1 1
    }
}

pcm.dmixer_a {
    type dmix
    ipc_key 1024
    slave {
        pcm "hw:0,3"
    }

    bindings {
        0 0
        1 1
    }
}