Picture encoder, picture decoder and corresponding methods of encoding and decoding

The present disclosure relates to adaptive filtering, e.g. adaptive loop filtering, which may be used during encoding and decoding of video pictures. In particular, the present disclosure provides for determining a zero coefficients map, in which each bit indicates whether or not a respective filter coefficient of a supporting region is to be included into the bitstream for an adaptive filter. An indication of the zero coefficients map is included into the bitstream before at least one filter coefficient of the adaptive filter indicated by the zero coefficients map as to be included into the bitstream. The provision of a zero coefficients map enables an efficient signaling and allows for flexible filter shapes that are particularly suitable for the content at hand.