With the microelectronic techniques and improvement on LED displays, fine pitch LED displays become a more popular solution for replacing indoor displays, such as commercial digital signage in the mall, meeting room, ballroom, TV studio, broadcast room, central control room, and even consumer TV. However, six challenges of fine pitch LED displays still haunt display manufacturers including lower ghosting, dim line at first scan line, uneven brightness, color shift, gradient dim line and cross effect caused by LED failure. These phenomena are obvious when displaying images with more grayscales at low brightness condition.