I am streaming music via iTunes to an AE without any difficulties. However, when I play a video within iTunes, the audio is directed to my iMac's built-in speakers. I'm certain there is a simple configuration step I have ignored which will correct this problem.

Any help appreciated in advance.

Are you using Airfoil?

iTunes itself will not stream anything but music via an Airport Express.

You need AirFoil.

There is a very good reason Apple does not support Airport Express sound for videos : the time lag is unacceptable (several seconds) between the video played on the screen and the sound coming out of Airport Express.
With Airfoil, you can get the video sound out of Airport Express, which is fine as long as you do not look at the screen...

so you've tried the Airfoil Video Player and it's not in sync?

http://www.macworld.com/article/132295/2008/02/airfoil3.html

so you've tried the Airfoil Video Player and it's not in sync?

http://www.macworld.com/article/132295/2008/02/airfoil3.html

I just downloaded Airfoil and am now listening to the Scottish BBC's piping program on my living room speakers... absolutely great! Thanks chefklc!

so you've tried the Airfoil Video Player and it's not in sync?

http://www.macworld.com/article/132295/2008/02/airfoil3.htmlYou are correct mentioning Airfoil Video Player is supposed to take care of the desynchronization issue.
However it was not an option for me since I use FrontRow.