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Error Control and Concealment for

Video Communication: A Review

The problem of error control and concealment in video communication is becoming increasingly important because of the growing interest in video delivery over unreliable channels such as wireless networks and the Internet. This paper reviews the techniques that have been developed for error control and concealment in the past 10–15 years. These techniques are described in three categories according to the roles that the encoder and decoder play in the underlying approaches. Forward error concealment includes methods that add redundancy at the source end to enhance error resilience of the coded bit streams. Error concealment by postprocessing refers to operations at the decoder to recover the damaged areas based on characteristics of image and video st, interactive error concealment covers techniques that are dependent on a dialogue between the source and destination. Both current research activities and practice in international standards are covered. Keywords—Error concealment, error control in video transport,video communications.

I. INTRODUCTION

One inherent problem with any communications system is that information may be altered or lost during trans mis sion due to channel noise. The effect of such information loss can be devastating for the transport of compressed video because any damage to the compressed bit stream may lead to objectionable visual distortion at the decoder. In addition, real-time/interactivity requirements exclude the deployment of some well-known error-recovery techniques for certain applications. Last, issues such as audio-visual synchronization and multipoint communications further complicate the problem of error recovery.Transmission errors can be roughly classified into two categories: random bit errors and erasure errors. Random bit errors are caused by the imperfections of physical channels, which result in bit inversion, bit insertion, and bit deletion. Depending on the coding methods and the affected information content, the impact of random bit errors can range from negligible to objectionable. When fixed-length

coding is used, a random bit error will only affect one code word, and the caused damage