Error concealment analysis for H.264/advanced video coding encoded video sequences

摘要

Error concealment methods have become very important in particular when transmitting video streams over error prone wireless links. Often a retransmission of corrupted sequences is not possible and thus the receiver has to make the best out of the received stream. The contributions of this article are the following: firstly, a performance comparison of various error concealment strategies (straight decoding, slice level concealment and macroblock level concealment) is presented based on the detection of errors, the exact location of which is unknown. Secondly, an analytical treatment of the slice level concealment, resulting in a precise mathematical model is provided. Finally, further improvements are proposed by subjective methods based on visual inspection and comparison of their performance by means of simulations.%The transmissions of data over wireless channels are affected by errors due to multiple causes, such as poor channel quality, interference and noise at the receiver. For some services, such as In-rnternet browsing or File Transport Protocol (FTP) traffic, the application requires the retransmission of incorrectly received packets. For video streaming applications, however, missing and damaged packets have to be handled differently. In broadcast and multicast transmissions, a retransmission of damaged or not received packets is not possible. A single source is serving several users and, even assuming the presence of a feedback channel, it cannot react to the needs of a single user since the data channel is typically shared by the plurality of users. Although possible in unicast transmissions, retransmission can also be problematic there. In case of network congestion, an overloaded cell may not be able to retransmit the damaged packet within the delay limit required by the dimension of a playout buffer (typically 3-6 s) (Sabeva et al. 2006; Levine et al. 2007).