Enhancement of one-dimensional variable-length DPCM images corrupted by transmission errors

Methods are presented for enhancing one-dimensional variable-length differential pulse-code modulation (VLDPCM) images corrupted by transmission errors, are presented. The proposed methods take advantage of the VLDPCM code´s high sensitivity to errors. Two methods are described. The first involves no increase of transmitted bit rate and consists of processing the corrupted image. The second method involves the transmission of additional information to enable an almost exact reconstruction of the original image. The amount of added redundancy can be reduced at the cost of performing more computations. In a simulation, the authors used less than 7% redundancy. Both methods achieve significant improvements which are demonstrated by the simulation results. The simulation results include original, corrupted, and enhanced images as well as the signal-to-noise ratio (SNR) versus bit-error rate (BER) curve. For BER 10^-3, the SNR (signal-to-noise ratio) gains for the first and second methods are greater than 17 and 44 dB, respectively