Phoronix: HDMI Audio Support For Intel G43/45 Chipsets

Initially the ATI R600 GPUs and later with the available open-source drivers (xf86-video-ati and xf86-video-radeonhd) hadn't supported using the graphics card's integrated audio processor with HDMI output. An end-user though dissatisfied with this had went on to reverse-engineer the support for RadeonHD HDMI audio support...

http://www.phoronix.com/vr.php?view=NjgzNg