Sounds very similar to the problem i've been having with my ice1712, see post
entitled 'ice1712 using dmix, loud crackle on all playback', however, i've
yet to receive a response and have unfortunately not made any progress, so
i've temporarily stopped using dmix.
Sorry i can't be of more help.
More information:
It is not connected with mmap, only dmix.
I've uncovered another problem, one can't connect rate plugin to dmix,
the effect is infinite silence.
Kernel
Linux uplink2 2.6.6-love4 #1 Tue May 18 21:09:25 CEST 2004 i686 AMD
Athlon(
