Camera Mapping with Video source

[dvrvdr]

Is there a drawback of using camera map feature with video footage? The render seems ok, but the assigned textures in edit window are distorted which makes it impossible to edit., i have to render the active view in order to edit,. is this because the footage have non square pixel asp.ratio or have fields? (altough i set the ratio)
the projection camera have a motion, captured from a cameratrack software,.
d