A video decoder is configured to, for a group of video blocks of the video data, determine a number of merged groups for a plurality of classes is equal to one merged group; receive a first flag indicating that filter coefficient information for at least one merged group is not coded in the video data; receive for the one merged group, a second flag, wherein a first value for the second flag indicates that filter coefficient information mapped to the one merged group is coded in the video data, and wherein a second value for the second flag indicates that the filter coefficient information mapped to the one merged group is all zero values; determine the second flag is equal to the second value; and determine one or more filters from the set of filters using the all zero values.