pcm.dmixer {
type dmix
ipc_key 2048
slave {
pcm "hw:1,7" # Always use pure hw. dmix will reformat/resample audio.
period_size 512 # If you get stuttering/or non-working audio, fiddle around with these
buffer_size 4096
rate 48000 # HDMI, I'll assume 48kHz
format S16_LE # Should be default for pretty much any soundcard.
}
bindings {
0 0
1 1
}
}

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