Control DMX512 from audio out
Not possible.  Your audio card has DACs that run at a maximum sample rate of 48 ksps, possibly up to 192 ksps if you have a really expensive professional card.  At 48 ksps, the maximum frequency you can synthesize is 24 kHz.  

I suggest looking at this libary: https://pypi.python.org/pypi/dmx/1.0 .  It is a python interface to a standard USB to DMX bridge box.  And here is a cheap USB to DMX cable that should work with that library: http://dmxking.com/usbdmx.  

This may also be a interesting project to look at: http://www.openlighting.org/ .  It seems they use a client/sever architecture to connect applications to DMX universes, and it works with a wide variety of USB DMX adapters.