# US 10,771,820 B2 · Image encoding method and apparatus using artifact reduction filter, and image decoding method and apparatus using artifact reduction filter > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,771,820 B2 - Document ID: US10771820B2 - Status: Granted - Kind: B2 - Application number: 16/105,616 - Filed: 2018-08-20 - Published: 2019-07-25 - Granted: 2020-09-08 - Earliest claimed: 2018-01-22 - Assignees: Samsung Electronics Co., Ltd.; Industry-Academic Cooperation Foundation, Yonsei University - Applicants: Samsung Electronics Co., Ltd.; Industry-Academic Cooperation Foundation, Yonsei University - Inventors: Sun-il Lee; Sangyoun Lee; Sanghoon Lee; Dosik Hwang; Changhyun Park; Sewoong Ahn; Jinseong Jang; Chan-yul Kim; Taeoh Kim; Taejoon Eo; Jongyoo Kim - Web page: https://patentgrep.com/patent/US10771820B2 ## CPC - H04N 19/117: Filters, e.g. for pre-processing or post-processing (sub-band filter banks H04N19/635) - H04N 19/86: involving reduction of coding artifacts, e.g. of blockiness - H04N 19/136: Incoming video signal characteristics or properties - H04N 19/154: Measured or subjectively estimated visual quality after decoding, e.g. measurement of distortion (use of rate-distortion criteria H04N19/147) - H04N 19/172: the region being a picture, frame or field - H04N 19/186: the unit being a colour or a chrominance component - H04N 19/70: characterised by syntax aspects related to video coding, e.g. related to compression standards - H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION ## Abstract Provided is an image encoding method including generating a first picture reconstructed by using a residual picture and a predicted picture; generating a second picture by applying a first artifact reduction filter to the first picture; determining a picture having a smaller bit-rate distortion cost from among the first and second pictures by comparing a first bit-rate distortion cost of the first picture with a second bit-rate distortion cost of the second picture; generating a third picture by applying an in-loop filter to the determined picture; generating a fourth picture by applying a second artifact reduction filter to the third picture; determining a picture having smaller distortion from among the third and fourth pictures by comparing first distortion of the third picture with second distortion of the fourth picture; and generating, via a processor, a bitstream including information about whether the second artifact reduction filter is applied. ## Claims ### Claim 1 An image encoding method comprising: generating a first picture reconstructed by using a residual picture and a predicted picture; generating a second picture by applying a first artifact reduction filter to the first picture; determining a picture having a smaller bit-rate distortion cost from among the first and second pictures by comparing a first bit-rate distortion cost of the first picture with a second bit-rate distortion cost of the second picture; generating a third picture by applying an in-loop filter to the determined picture; generating a fourth picture by applying a second artifact reduction filter to the third picture; evaluating subjective quality and objective quality of each of the third and fourth pictures so as to determine a first distortion of the third picture and a second distortion of the fourth picture; determining a picture having smaller distortion from among the third and fourth pictures by comparing the first distortion with the second distortion; and generating, via a processor, a bitstream comprising information about whether the second artifact reduction filter is applied, wherein the evaluating the subjective quality comprises evaluating the subjective quality of each of the third and fourth pictures based on a size of a display and a distance between the display and a viewer, and wherein the evaluating the subjective quality comprises determining sharpness of each of the third and fourth pictures, based on sharpness of each of blocks in the third and fourth pictures. ### Claim 2 (depends on 1) The image encoding method of claim 1, wherein the sharpness of each of the blocks is determined according to respective modes of the blocks, and wherein the modes are determined according to whether each of the blocks is a motion region and whether each of the blocks is a texture region or an edge region. ### Claim 3 (depends on 2) The image encoding method of claim 2, wherein the sharpness of each of the third and fourth pictures is determined by applying a weight to the sharpness of each of the blocks, the weight varying according to the size of the display and the distance between the display and the viewer. ### Claim 4 (depends on 1) The image encoding method of claim 1, wherein the evaluating the subjective quality and the objective quality comprises: extracting a first colorfulness feature point, a first contrast feature point, and a first sharpness feature point from the third picture; extracting a second colorfulness feature point, a second contrast feature point, and a second sharpness feature point from the fourth picture; extracting a third colorfulness feature point, a third contrast feature point, and a third sharpness feature point from a high dynamic range (HDR) picture; evaluating the objective quality of the third picture, based on a first difference between the first colorfulness feature point of the third picture and the third colorfulness feature point of the HDR picture, a second difference between the first contrast feature point of the third picture and the third contrast feature point of the HDR picture, and a third difference between the first sharpness feature point of the third picture and the third sharpness feature point of the HDR picture; and evaluating the objective quality of the fourth picture, based on a fourth difference between the second colorfulness feature point of the fourth picture and the third colorfulness feature point of the HDR picture, a fifth difference between the second contrast feature point of the fourth picture and the third contrast feature point of the HDR picture, and a sixth difference between the second sharpness feature point of the fourth picture and the third sharpness feature point of the HDR picture. ### Claim 5 (depends on 1) The image encoding method of claim 1, further comprising updating the second artifact reduction filter so as to reduce the first distortion of the third picture and the second distortion of the fourth picture, based on the evaluated subjective quality and the evaluated objective quality. ### Claim 6 (depends on 1) The image encoding method of claim 1, wherein the first artifact reduction filter is applied to a coding unit, and the second artifact reduction filter is applied to a slice unit. ### Claim 7 (depends on 1) The image encoding method of claim 1, wherein the first artifact reduction filter and the second artifact reduction filter are identical. ### Claim 8 (depends on 1) A non-transitory computer-readable recording medium having recorded thereon a program for executing the image encoding method of claim 1. ### Claim 9 An image decoding method comprising: receiving a bitstream comprising information about whether to apply an artifact reduction filter after an in-loop filter is applied; reconstructing a picture by performing decoding on the bitstream; when the information indicates that the artifact reduction filter is to be applied after the in-loop filter is applied, applying the second artifact reduction filter to the reconstructed picture to which the in-loop filter has been applied; and when the information indicates that the artifact reduction filter is not to be applied after the in-loop filter is applied, outputting the reconstructed picture to which the in-loop filter has been applied. ### Claim 10 An image encoding apparatus comprising: a first artifact reduction filter applier configured to generate a first picture reconstructed by using a residual picture and a predicted picture, and generate a second picture by applying a first artifact reduction filter to the first picture; a bit-rate distortion cost comparator configured to determine a picture having a smaller bit-rate distortion cost from among the first and second pictures by comparing a first bit-rate distortion cost of the first picture with a second bit-rate distortion cost of the second picture; a second artifact reduction filter applier configured to generate a third picture by applying an in-loop filter to the determined picture, and generate a fourth picture by applying a second artifact reduction filter to the third picture; a distortion comparator configured to evaluate subjective quality and objective quality of each of the third and fourth pictures so as to determine a first distortion of the third picture and a second distortion of the fourth picture and determine a picture having smaller distortion from among the third and fourth pictures by comparing the first distortion with the second distortion; and a bitstream generator configured to generate a bitstream comprising information about whether the second artifact reduction filter is applied, wherein the distortion comparator is further configured to evaluate the subjective quality of each of the third and fourth pictures based on a size of a display and a distance between the display and a viewer, and determine sharpness of each of the third and fourth pictures, based on sharpness of each of blocks in the third and fourth pictures. ### Claim 11 (depends on 10) The image encoding apparatus of claim 10, wherein the sharpness of each of the blocks is determined according to respective modes of the blocks, and wherein the modes are determined according to whether each of the blocks is a motion region and whether each of the blocks is a texture region or an edge region. ### Claim 12 (depends on 11) The image encoding apparatus of claim 11, wherein the sharpness of each of the third and fourth pictures is determined by applying a weight to the sharpness of each of the blocks, the weight varying according to the size of the display and the distance between the display and the viewer. ### Claim 13 (depends on 10) The image encoding apparatus of claim 10, wherein the distortion comparator is further configured to: extract a first colorfulness feature point, a first contrast feature point, and a first sharpness feature point from the third picture, extract a second colorfulness feature point, a second contrast feature point, and a second sharpness feature point from the fourth picture, extract a third colorfulness feature point, a third contrast feature point, and a third sharpness feature point from a high dynamic range (HDR) picture, evaluate the objective quality of the third picture, based on a first difference between the first colorfulness feature point of the third picture and the third colorfulness feature point of the HDR picture, a second difference between the first contrast feature point of the third picture and the third contrast feature point of the HDR picture, and a third difference between the first sharpness feature point of the third picture and the third sharpness feature point of the HDR picture, and evaluate the objective quality of the fourth picture, based on a fourth difference between the second colorfulness feature point of the fourth picture and the third colorfulness feature point of the HDR picture, a fifth difference between the second contrast feature point of the fourth picture and the third contrast feature point of the HDR picture, and a sixth difference between the second sharpness feature point of the fourth picture and the third sharpness feature point of the HDR picture. ### Claim 14 (depends on 10) The image encoding apparatus of claim 10, further comprising a second artifact reduction filter updater configured to update the second artifact reduction filter so as to reduce the first distortion of the third and the second distortion of the fourth picture, based on the evaluated subjective quality and the evaluated objective quality. ### Claim 15 (depends on 10) The image encoding apparatus of claim 10, wherein the first artifact reduction filter is applied to a coding unit, and the second artifact reduction filter is applied to a slice unit.