Signalling of filtering information

A method for encoding video data, the method comprising:

• determining a set of filters for a group of video blocks of the video data;
• determining sets of filter coefficient information for the group of video blocks;
• determining a number of merged groups for a plurality of classes, wherein each class of the plurality of classes has corresponding values for metrics, wherein each class of the plurality of classes is mapped to a filter from the set of filters, and wherein each merged group comprises one or more classes that are mapped to a same set of filter coefficient information;
• determining the number of merged groups for the plurality of classes is equal to one, indicating that the plurality of classes includes one merged group;
• generating, for inclusion in the video data, a first flag set to a first value, wherein the first value for the first flag indicates that filter coefficient information for at least one of the merged groups is not coded in the video data and a second value for the first flag indicates that filter coefficient information for all of the merged groups is coded in the video data;
• generating, for inclusion in the video data, a second flag set to a second value, 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 the second value for the second flag indicates that the filter coefficient information mapped to the one merged group is all zero values.

A device for decoding video data, the device comprising:

• a memory configured to store the video data;
• and
• one or more processors configured to:
• for a group of video blocks of the video data, determine a number of merged groups for a plurality of classes, wherein each class of the plurality of classes has corresponding values for metrics, wherein each class of the plurality of classes is mapped to a filter from a set of filters, and wherein each merged group comprises one or more classes that are mapped to same filter coefficient information;
• determine the number of merged groups for the plurality of classes is equal to one, indicating that the plurality of classes includes one merged group;
• receive, in the video data, for the group of video blocks, a first flag, wherein a first value for the first flag indicates that filter coefficient information for at least one of the merged groups is not coded in the video data and a second value for the first flag indicates that filter coefficient information for all of the merged groups is coded in the video data;
• determine that the first flag is equal to the first value;
• receive, in the video data, 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.

A device for encoding video data, the device comprising:

• a memory configured to store video data;
• and
• one or more processors configured to:
• determine a set of filters for a group of video blocks of the video data;
• determine sets of filter coefficient information for the group of video blocks;
• determine a number of merged groups for a plurality of classes, wherein each class of the plurality of classes has corresponding values for metrics, wherein each class of the plurality of classes is mapped to a filter from the set of filters, and wherein each merged group comprises one or more classes that are mapped to a same set of filter coefficient information;
• determine the number of merged groups for the plurality of classes is equal to one, indicating that the plurality of classes includes one merged group;
• generate, for inclusion in the video data, a first flag set to a first value, wherein the first value for the first flag indicates that filter coefficient information for at least one of the merged groups is not coded in the video data and a second value for the first flag indicates that filter coefficient information for all of the merged groups is coded in the video data;
• generate, for inclusion in the video data, a second flag set to a second value, 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 the second value for the second flag indicates that the filter coefficient information mapped to the one merged group is all zero values.