DETECTION AND CORRECTION OF TRANSMISSION ERRORS IN JPEG IMAGES

In this study, the detection and correction approach to transmission e rrors in Joint Photographic Experts Group (JPEG) images using the sequ ential discrete cosine transform (DCT)-based mode of operation is prop osed. The objective of the proposed approach is to eliminate transmiss ion errors in JPEG images, Here a transmission error may be either a s ingle-bit error or a burst error containing N successive error bits, F or an entropy-coded JPEG image, a single transmission error in a codew ord will not only affect the underlying codeword, but may also affect subsequent codewords. Consequently, a single error in an entropy-coded system may result in a significant degradation. To cope with the sync hronization problem, in the proposed approach the restart capability o f JPEG images is enabled, i.e., the eight unique restart markers (sync hronization codewords) are periodically inserted into the JPEG compres sed image bitstream, Transmission errors in a JPEG image are sequentia lly detected both when the JPEG image is under decoding and after the JPEG image has been decoded, When a transmission error or equivalently a corrupted restart interval is detected, the proposed error correcti on approach simply performs a sequence of bit inversions and redecodin g operations on the corrupted restart interval and selects the ''best' ' feasible redecoding solution by using a proposed cost function for e rror correction, Based on the simulation results obtained in this stud y, the proposed approach can recover high-quality JPEG images from the corresponding corrupted JPEG images at bit error rates (BER's) up to approximately 0.4%. This shows the feasibility of the proposed approac h.