An implicit DST-based filter having characteristics defined by a linear convolution kernel that may be causal or noncausal-symmetric. The filter filters an information signal composed of blocks of discrete cosine transform (DCT) coefficients to generate a filtered information signal also composed of blocks of DCT coefficients. The filter comprises multiplying matrices, a deriving module, matrix multiplying modules and a summing module. The multiplying matrices are obtained by absorbing a cosine-to-sine transform and a sine-to-cosine transform into kernel matrices derived from the linear convolution kernel. The deriving module derives intermediate blocks of DCT coefficients from neighboring ones of the blocks of DCT coefficients constituting the information signal. The matrix multiplying modules multiply the intermediate blocks of DCT coefficients by the multiplying matrices. The summing module sums the blocks of DCT coefficients generated by the matrix multiplying modules to generate the blocks of DCT coefficients constituting the filtered information signal.