[scorpion]

From your description it appears that the audio works as you can use quicktime.

I do not have enough information to troubleshoot the situation. You may have to take the DVR to a repair shop local to you so that they can take a look at it. I do not know if it would be a codec problem, but I doubt it otherwise the internet would be full of users with the same complaint. This makes the situation unique to you. I would have to set it up locally to me in order to see what the issue is.