Reliable video communications over error-prone networks has been a very challenging task. During video transmission, packet losses may occur due to channel errors, especially over those relatively unreliable networks, e.g. wireless networks. In many real-time applications, the retransmission of video data is not feasible because of the application natures. Thus, it is important to develop approaches to recover the lost video data and "conceal" the errors when packet losses occur. This book (thesis) provides a comprehensive study on "error concealment" techniques employed in modern video communication systems, and proposes new approaches to this field as well as extensive evaluation results.