Programming :: Play Multiple Sound Streams On ALSA Dmix?

I'm having trouble getting ALSA to play multiple sound streams (multiple sounds at once). My code is running on an embedded ARM board using a AC97 sound. It will only play one without any mixing, I have to use pure ALSA as higher sound mixers are a nightmare to cross compile for ARM. I've tested my system with aplay for example

aplay -D plughw:0,1 bang.wav

works fine. So I tried dmix with

aplay -D plug:dmix Win.wav

That gave the following error

ALSA lib pcm_direct.c:1587snd_pcm_direct_parse_open_conf) The field ipc_gid must be a valid group (create group audio)
aplay: main:550: audio open error: Invalid argument

I checked asound with

/etc # cat asound.conf
pcm.EP93XX {
type hw

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Does this mean dmix will not work? Is there someway with the above setup I can play multiple sounds? I have to use the vendor ALSA build (so can't update ALSA), I can change the .confs however. Also because I'm cross compiling things like pulseaudio SDL are very difficult to get working, so I basically need to use the above ALSA. Is there anyway I can find if dmix exists on the system?

Should add aplay -L does show dmix ?
iec958 'cards.pcm.iec958'
spdif 'cards.pcm.iec958'

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