Forward error control for packet loss and corruption

Many techniques have been proposed to protect media data against channel errors. One possible approach is error-resilient source coding, which includes packetization of the information bit stream into independently decodable packets, exploitation of synchronization markers to control error propagation, reversible variablelength coding, and multiple description coding. Another approach is based on er-ror concealment, where the lost or corrupted data is estimated at the receiver side with, for example, interpolation. Error control for media data may also exploit error detection and retransmission (ARQ, see Chapter 7). One further approach is forward error correction (FEC) with error correcting codes. Finally, one may combine any of the aforementioned methods. The choice of an appropriate error control method is not easy because it requires a deep understanding of both the source and the channel. In this respect, many important questions have to be answered: What is the type of the data? Is the data compressed? If yes, what is the compression scheme used? Is the data being transmitted over a wireline or a wireless network? Is there a feedback channel? What are the channel conditions? Moreover, the user requirements must also be taken into consideration. What is more important: reconstruction fidelity or transmission speed?