Method and apparatus for deblocking filtering a block of pixels
A method of filtering a block of pixels in an image, comprising obtaining a first clipping control parameter (tc) value based on a quantization parameter of the block; comparing a first value of a first pixel located on one side of an edge in said block and a second value of a second pixel located on the other side of the edge in said block with a predetermined threshold derived from the first clipping control parameter value; and determining whether to apply a strong filtering to the first pixel based on the result of the comparison, wherein: the strong filtering comprises filtering the first pixel value so that the filtered first pixel value differs from the first pixel value by no more than a range value based on the clipping control parameter (tc), the ration between two range values corresponding to successive values of bitdepths being strictly lower than 2.
1. A method of deblocking filtering for an image, the method comprising:
obtaining a first parameter value for deblocking filtering based on a second parameter value; and
obtaining a filtered sample value by performing deblocking filtering on a sample in a block of samples by using the first parameter value, the filtered sample value being limited by a range based on the first parameter value,
wherein obtaining the first parameter value comprises:
obtaining the second parameter value based on a quantization parameter value used for decoding the block of samples; and
obtaining the first parameter value by adding an offset to the second parameter value, using a parameter value indicating a bit-depth of the image to obtain a value f, and dividing the result of the adding by 2 f .
2. The method according to claim 1 , wherein the offset varies according to the bit-depth of the image.
3. The method according to claim 1 , wherein the second parameter value is obtained from a table associating the value with the quantization parameter value.
4. An apparatus for deblocking filtering for an image, the apparatus comprising:
an obtaining unit configured to obtain a first parameter value for deblocking filtering; and
a filtering unit configured to obtain a filtered sample value by performing deblocking filtering based on a second parameter value on a sample in a block of samples by using the first parameter value, the filtered sample value being limited by a range based on the first parameter value,
wherein the obtaining unit is configured to obtain the second parameter value based on a quantization parameter value used for decoding the block of samples, and
to obtain the first parameter value by adding an offset to the second parameter value, using a parameter value indicating a bit-depth of the image to obtain a value f, and dividing the result of the adding by 2 f .
5. The apparatus according to claim 4 , wherein the offset varies according to the bit-depth of the image.
6. The apparatus according to claim 4 , wherein the second parameter value is obtained from a table associating the value with the quantization parameter value.
7. A non-transitory computer readable storage medium containing computer-executable instructions which causes a computer to perform a method for deblocking filtering for an image, the method comprises:
obtaining a first parameter value for deblocking filtering based on a second parameter value; and
obtaining a filtered sample value by performing deblocking filtering on a sample in a block of samples by using the first parameter value, the filtered sample value being limited by a range based on the first parameter value,
wherein obtaining the first parameter value comprises:
obtaining the second parameter value based on a quantization parameter value; and
obtaining the first parameter value for deblocking filtering by adding an offset to the second parameter value, using a parameter value indicating a bit-depth of the image to obtain a value f, and dividing the result of the adding by 2 f .