In DCT based video coding standards, output bit rates are highly varied by the characteristics and coding types of picture. To stably transmit the good quality of pictures, a rate control algorithm is needed. A rate is controlled mainly by appropriate quantization parameter QP with regard to the channel rate. In conventional approaches, R-D characteristics are analyzed in terms of the rate-QP and the distortion-QP relation. However, the proposed rate control algorithm is based on so-called ρ-domain R-D analysis. ρ is defined as the percentage of zero coefficients of a frame, and is known to be strongly correlated with the actual coding bit rate. Using the characteristics of rate-ρ relation, the linear rate model R($\Rho$) is constructed. The simple rate estimation method that is based on a variable length code table, is proposed to construct the rate function. After the rate function R($\Rho$) is estimated, rate model updating follows in the macroblock-level for refining the rate model. As compared with TMN8 rate control, the proposed rate control algorithm provides more accurate rate regulation and better buffer regulation performance. The proposed rate control is also advantageous to maintain the better quality of picture since it has smaller QP variation than TMN8 rate control in a frame. These experimental results confirms the fact that the proposed rate control algorithm is highly competitive to TMN8 rate control or even outperforms it.
