Virtual boundary processing for adaptive loop filtering

An apparatus, the apparatus comprising:

• processing circuitry;
• and
• a memory, the memory containing instructions executable by the processing circuitry, wherein the apparatus is configured to:
• obtain a coding tree block (CTB) having a vertical size (CtbSizeY) and a horizontal size (CtbSizex), the CTB comprising set of sample values associated with the image, the set of sample values comprising a current sample value having a location (x,y) within the CTB, where x is a horizontal value and y is a vertical value;
• select a filter strength value for the current sample based on y;
• and
• filter the current sample using the selected filter strength value, wherein
• selecting a filter strength value for the current sample based on y comprises:
• i) determining whether the following first condition is true:
• (
• y
• ==
• (
• CtbSizeY
• -
• 5
• )
• ⁢
• ⁢
• OR
• ⁢
• ⁢
• y
• ==
• (
• CtbSizeY
• -
• 4
• )
• )
• ⁢
• ⁢
• AND
• ⁢
• ⁢
• var
• ==
• 1
• ,
• where var is a variable that is set equal to 1 as a result of a determination that a second condition is satisfied;
• and
• ii) choosing a filter strength value of 10 as a result of determining that the first condition is true.

An video decoder, the video decoder comprising:

• processing circuitry;
• and
• a memory, the memory containing instructions executable by the processing circuitry, wherein the video decoder is configured to:
• receive a bitstream;
• obtain, from information in the bitstream, a coding tree block (CTB) having a vertical size (CtbSizeY) and a horizontal size (CtbSizex), the CTB comprising set of sample values associated with the image, the set of sample values comprising a current sample value having a location (x,y) within the CTB, where x is a horizontal value and y is a vertical value;
• select a filter strength value for the current sample based on y;
• and
• filter the current sample using the selected filter strength value, wherein
• selecting a filter strength value for the current sample based on y comprises:
• i) determining whether the following first condition is true:
• (y==(CtbSizeY−5) OR y==(CtbSizeY−4)) AND var==1,
• where var is a variable that is set equal to 1 as a result of a determination that a second condition is satisfied;
• and
• ii) choosing a filter strength value of 10 as a result of determining that the first condition is true.

A computer program product (CPP) comprising non-transitory computer readable medium storing a computer program comprising instructions which when executed by processing circuitry causes the processing circuitry to perform a method comprising:

• obtaining a coding tree block (CTB) having a vertical size (CtbSizeY) and a horizontal size (CtbSizex), the CTB comprising set of sample values associated with the image, the set of sample values comprising a current sample value having a location (x,y) within the CTB, where x is a horizontal value and y is a vertical value;
• selecting a filter strength value for the current sample based on y;
• and
• filtering the current sample using the selected filter strength value, wherein
• selecting a filter strength value for the current sample based on y comprises:
• i) determining whether the following first condition is true:
• (
• y
• ==
• (
• CtbSizeY
• -
• 5
• )
• ⁢
• ⁢
• OR
• ⁢
• ⁢
• y
• ==
• (
• CtbSizeY
• -
• 4
• )
• )
• ⁢
• ⁢
• AND
• ⁢
• ⁢
• var
• ==
• 1
• ,
• where var is a variable that is set equal to 1 as a result of a determination that a second condition is satisfied;
• and
• ii) choosing a filter strength value of 10 as a result of determining that the first condition is true.