An adaptive loop filter utilizing separable filters within a quadtree-based adaptive loop filter (QALF). The filters for at least the P and B pictures are replaced with a separable filter to provide Separable QALF (SQALF). In a preferred embodiment the filter comprises a Wiener filter as a best fit approximation of the non-separable filter. In response to decoding with the SQALF approach, computational complexity in the decoder is reduced without lowering perceived visual quality. Estimation of the separable filter is obtained in the encoder by iteratively minimizing the sum of squares error with the separable filter. The SQALF filtering is described within a video decoder.