This paper proposes an efficient Unbalanced Multiple Description Scalar Quantisation (U-MDSQ) method for video streaming over asymmetric channels. In order to control the asymmetric target rates for each coded descriptions, the UMDSQ parameters are combined with the rate control method based on the existing linear relationship between rate and percentage of zeros in transform coefficients in MDSQ domain. The simulation results show that the proposed method exhibits high accuracy for a wide range of target bitrates and unbalanced rates between descriptions. Moreover, the obtained results show the effectiveness of the proposed method in order to improve the overall performance over channels with asymmetric rate and packet loss rate (PLR) conditions, when compared with Balanced MDSQ. This method finds application in video streaming with path diversity based on Multiple Description Coding (MDC) with dynamic channel conditions.