Q: Audio doesn't work smoothly via HDMI

I've connected my imac (21.5/late 2009) to my sony tv using a Mini DisplayPort to HDMI adaptor. The sound works but every few seconds there is a gap in the audio for two seconds. how can i fix this? when i try playing music it works fine, but when i add the video it occurs. seems like it happens because there is an overload of data transfer..