Asymmetric video coding based on binocular suppression provides a prospect for improving coding efficiency since one view in stereoscopic video can be encoded at lower bitrates than the other view without a loss of perceptual video quality. In this paper, we propose a joint rate control scheme for asymmetric stereoscopic video coding in a hybrid video codec system, which supports binocular suppression-based asymmetric stereoscopic video coding in a theoretical basis within an optimization framework. To obtain an optimal solution to quantization steps for joint rate control, we apply the Karush-Kuhn-Tucker (KKT) conditions in minimizing the perceptual distortion of decoded video under the conditions that: 1) the sum of bits generated from two video encoders is constrained within a given bit budget; 2) the quality of a primary view is superior to that of an auxiliary view with an allowable difference between two view qualities; and 3) the distortion of an auxiliary view is less than a given threshold value for high bitrate encoding. As a result, the proposed rate control scheme effectively enhances the perceptual quality based on an optimization framework by taking into account the binocular suppression and also simultaneously controlling the rates of both the left and right views of stereoscopic video under the constraints with a given target bit budget and an allowed quality difference. Experimental results demonstrate that, compared with the independent rate control scheme, the proposed joint rate control scheme with KKT conditions for asymmetric stereoscopic video coding not only demonstrates comparable 3-D perceived visual quality with an overall gain of 0.33 dB, but also attains 2-D visual quality gain by an average of 2.49 dB while accurately satisfying the given constraints in the proposed optimization framework.