Wrong screen size in WP8-XAML project

Hi,

I am running my project with 720p emulator which means 1280x720 resolution, but m_renderTargetSize shows the screensize as 853x480. Same happening with WXGA emulator , screensize shown is as 800x480. It is showing proper screen size only for WVGA emulatior which is 800x480.

I am not getting where the screen size is getting changed !

Any help over this ?

Thanks,
Anurag