Macroblock data classification and nonlinear bit count estimation for low delay H.263 rate control

A new rate control method for low delay transmission of H.263 coded video is presented. The method is based on nonlinear MMSE (minimum mean squared error) estimation of the number of coding bits of a macroblock. A class is determined for each macroblock from its coding mode and quantized simple statistics of its data. Each combination of macroblock class and quantization parameter is mapped to a nonlinear estimate which is designed either offline or online from empirical data. The quantization parameters of macroblocks of a frame are determined to attain near uniform spatial reconstruction quality as the total estimate of the number of coding bits closely approximates the targeted number of bits for the frame satisfying the delay and encoder buffer size constraints. Simulations demonstrate that the accuracy of the new macroblock layer rate control method is significantly better than the method of TMN5 and very competitive with the method of TMN8.