A PERCEPTUALLY OPTIMIZED 3-D SUBBAND CODEC FOR VIDEO COMMUNICATION OVER WIRELESS CHANNELS

Visual communication over wireless channels is becoming an important s ervice in multimedia communications, Because of the limited bandwidth and high error rates of the wireless channel, the video codec should b e designed tee have high coding efficiency in maintaining acceptable v isual quality at low bit rates and robustness to suppress the distorti on due to transmission errors, In this paper, the coding efficiency of a 3-D subband video codec is optimized by removing not only the redun dancy due to spatial and temporal correlation but also perceptually in significant components from video signals. Unequal error protection is applied to the source code bits of different perceptual importance, A n error concealment method is employed to hide the distortion due to e rroneous transmission of perceptually important signals. The evaluatio n of each signal's perceptual importance is made first from measuring the just-noticeable distortion (JND) profile as the perceptual redunda ncy inherent in video signals, and then from allocating JND energy to signals of different subbands according to the sensitivity of human vi sual responses to spatio-temporal frequencies, Simulation results show that acceptable visual quality can be maintained in transmitting vide o sequences with low bit rates (< 64 kbps) over the wireless channel o f high error rates (up to BER = 10(-2)), and the distortion due to err oneous transmission of coded data can be effectively suppressed, In th e simulation, the noisy channel is assumed to be corrupted by the rand om errors depending on the average strength of the received wave and t he burst errors due to Rayleigh fading.