Optimal error protection for real time image and video transmission

In this paper a novel and computationally inexpensive analytic mean square error (MSE) distortion rate (D-R) estimator for SPIHT which generates a nearly exact distortion rate (D-R) function for the 2D and 3D SPIHT algorithm is presented. The analytical formula is derived from the observations that for any bit-plane coder, the slope of the D-R curve is constant for each level of the bit plane. Furthermore the slope of D-R curve reduces by a factor proportional to the level of the bit plane. An application of the derived results is presented in the area of 2D SPIHT transmission employing a binary symmetric channel (BSC) and Reed Solomon (RS) forward error correction (FEC) codes. Utilizing our D-R estimate, we employ unequal error protection (UEP) and equal error protection (EEP) in order to minimize the end to end mean square error (MSE) distortion of the transform domain. UEP yields a significant performance gain relative to EEP only when the average number of parity bits for a group of packets is constrained. When both the source rate and channel code rate varied under a bit budget constraint, optimal UEP yields only a slight improvement over the optimal EEP. A major contribution of this paper is the simple and extremely accurate analytical D-R model which potentially improves upon pre-existing methodologies and applications that rely on an accurate and computationally inexpensive D-R estimate. Another important contribution is that the optimum EEP, which requires almost no header information and can easily be computed using our method, is only slightly worse than the optimum UEP.