Mixing + HDMI audio

[Felix Natter <fnatter@gmx.net>]

hi,

my HDMI audio device works fine with one application (Flash, aplay, pidgin),
but not if some sources play at the same time (i.e. I watch a video and
want to get pidgin notification sounds while at it).

I used the 'hdmi' device:

$ aplay -L
default
    Playback/recording through the PulseAudio sound server
hdmi:CARD=MID,DEV=0
    HDA Intel MID, HDMI 0
    HDMI Audio Output
sysdefault:CARD=PCH
    HDA Intel PCH, ALC887-VD Analog
    Default Audio Device
front:CARD=PCH,DEV=0
    HDA Intel PCH, ALC887-VD Analog
    Front speakers
surround40:CARD=PCH,DEV=0
    HDA Intel PCH, ALC887-VD Analog
    4.0 Surround output to Front and Rear speakers
surround41:CARD=PCH,DEV=0
    HDA Intel PCH, ALC887-VD Analog
    4.1 Surround output to Front, Rear and Subwoofer speakers
surround50:CARD=PCH,DEV=0
    HDA Intel PCH, ALC887-VD Analog
    5.0 Surround output to Front, Center and Rear speakers
surround51:CARD=PCH,DEV=0
    HDA Intel PCH, ALC887-VD Analog
    5.1 Surround output to Front, Center, Rear and Subwoofer speakers
surround71:CARD=PCH,DEV=0
    HDA Intel PCH, ALC887-VD Analog
    7.1 Surround output to Front, Center, Side, Rear and Woofer speakers
iec958:CARD=PCH,DEV=0
    HDA Intel PCH, ALC887-VD Digital
    IEC958 (S/PDIF) Digital Audio Output

and then, if another source like flash is playing:

$ LANG=C aplay /usr/share/sounds/purple/send.wav -D hdmi
aplay: main:722: audio open error: Device or resource busy

I tried the solution mentioned here:
https://wiki.archlinux.org/index.php/Advanced_Linux_Sound_Architecture#Software_mixing_.28dmix.29
but this did not change anything :-/

Do I have to try the hacks described here, or is there possibly an
easier solution (like not breaking pulseaudio apps)?
https://wiki.archlinux.org/index.php/Advanced_Linux_Sound_Architecture#Troubleshooting

Thank you very much,
-- 
Felix Natter