* @param zoom_factor a floating point number describing the zoom factor. A value 1.0 corresponds to no zoom applied.
* @param cx a floating point number pointing the horizontal center of the zoom to be applied. This value should be between 0.0 and 1.0.
* @param cy a floating point number pointing the vertical center of the zoom to be applied. This value should be between 0.0 and 1.0.
*
* @deprecated use linphone_call_zoom instead
* cx and cy are updated in return in case their coordinates were too excentrated for the requested zoom factor. The zoom ensures that all the screen is fullfilled with the video.