A perceptually optimized 3-D subband codec for video communication over wireless channels

Visual communication over wireless channels is becoming important in multimedia. Because of the limited bandwidth and high error rates of the wireless channel, the video codec should be designed to have high coding efficiency in maintaining acceptable visual quality at low bit rates and robustness to suppress the distortion due to transmission errors. The coding efficiency of a 3D subband video codec is optimized by removing not only the redundancy due to spatial and temporal correlation but also perceptually insignificant components from video signals. Unequal error protection is applied to the source code bits of different perceptual importance. An error concealment method is employed to hide the distortion due to erroneous transmission of perceptually important signals. The evaluation of each signal's perceptual importance is made first from measuring the just-noticeable distortion (JND) profile as the perceptual redundancy inherent in video signals, and then from allocating JND energy to signals of different subbands according to the sensitivity of human visual responses to spatio-temporal frequencies. Simulation results show that acceptable visual quality can be maintained in transmitting video sequences with low bit rates (<64 kbps) over the wireless channel of high error rates (up to BER=10/sup -2/), and the distortion due to erroneous transmission of coded data can be effectively suppressed. In the simulation, the noisy channel is assumed to be corrupted by the random errors depending on the average strength of the received wave and the burst errors due to Rayleigh fading.