Method and device for deblocking-filtering, and method and device for encoding and decoding using same

A decoding apparatus for decoding a video signal, comprising:

• a residual data decoding unit configured to decode a residual block by performing inverse quantizing and inverse transforming;
• a prediction unit configured to generate a prediction block;
• an adder configured to reconstruct pixels of a reconstructed block by adding the prediction block and the residual block;
• and
• a deblocking filter unit configured to perform deblocking filtering on a block edge corresponding to the reconstructed block, based on whether the block edge corresponds to an edge between prediction blocks as well as whether the block edge corresponds to an edge between transform blocks,
• wherein the deblocking filter unit performs the deblocking filtering by using at least one of
• a first filtering mode which corresponds to a first filtering strength and updates six pixels adjacent to the block edge;
• and
• a second filtering mode which corresponds to a second filtering strength and updates four or fewer pixels adjacent to the block edge, the first filtering strength being stronger than the second filtering strength,
• wherein the second filtering mode
• calculates a delta value by using
• (i) a first difference between a first most neighboring pixel to the block edge and a second most neighboring pixel to the block edge,
• (ii) a second difference between two pixels which are adjacent to the first most neighboring pixel and the second most neighboring pixel respectively and have the same distance from the block edge, and
• (iii) an offset value, and
• updates the first most neighboring pixel and the second most neighboring pixel by using the delta value,
• wherein an absolute value of a coefficient value corresponding to the second difference is larger than 1/16 and smaller than the offset value,
• wherein the deblocking filter unit determines number of filtering target pixels based on a predetermined criteria, and wherein
• number of the filtering target pixels included in a first block corresponding to the block edge is different from number of the filtering target pixels included in a second block corresponding to the block edge.