This paper proposes a new normalized pammetric rate-distortion model which can be efficiently applied to H.263 compatible video codes and other codes of similar type. The model is very efficient in terms of computational complexity and amount of required memory since it approximates all 31 rate-distortion relations (one for each quantization parameter QP) with only one curve by normalizing the energy of signals and the quantization distortion with functions of QP. We show how the model parameters can be obtained from experimental data. We also propose a quantizer selection scheme which uses the model to estimate the number of bits required for encoding 8 x 8 residual blocks. Experiments show that the model provides very good approximations of the rate and the proposed quantizer selection scheme works better than the scheme used in [3].