Efficient decisions for deblocking

An apparatus for processing an image to provide deblocking filtering, the image being divided into a plurality of blocks, each block including a plurality of pixel lines perpendicular to a boundary with an block, the apparatus comprising:

• a processor;
• and
• a non-transitory memory having stored thereon executable instructions, which when executed, cause the processor to perform the steps of:
• dividing one or more of the plurality of blocks into a plurality of portions fewer than the plurality of pixel lines, each of the plurality of portions consisting of one or more pixel lines;
• calculating a decision value for each of the plurality of portions of a block based on values of pixels in a subset of pixel lines of the block;
• and
• judging whether or not to apply a deblocking filter to each of the plurality of portions of the block based on the respective decision value calculated for the portion,
• wherein the step of judging whether or not to apply a deblocking filter to each portion includes the step of:
• comparing the respective decision value calculated for the portion with a threshold value.