Apple TV airplay only sound no picture for wireless devices iphone, ipad

I am facing strange issue . I have apple TV (Generation2 ) with updated latest softwared version and i have Apple Extreme airport. and I have apple ipad (Generation 2) . All device firware and os version is upto dated.

If I airplay my phone or ipad for apple tv , only sound comes, no video. But I do airplay from itune software on my windows desktop machine. I can able to see video and audio. My windows machine is connected to mode through ethernet cable.

What can be the issue.

regards

Ravi