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We propose an efficient method for separable symmetric linear filtering in the discrete cosine transform (DCT) domain. First, separable two-dimensional (2-D) linear filtering is decomposed into the cascade of one-dimensional filtering in the DCT domain. We investigate special characteristics of DCT domain filtering matrices when the filter coefficients are symmetric. Then we present the DCT-domain 2-D filtering method using these characteristics. The proposed method requires a smaller number of multiplications including the typical sparseness of DCT coefficients compared to previous DCT-domain linear filtering methods. Also, the proposed method is composed of simple and regular operations, which would be appropriate for efficient very large scale integration implementation.