Image encoding/decoding method and device, and recording medium storing bitstream
The present invention relates to an image encoding and decoding method. An image decoding method for the same may include: obtaining transform coefficients of a current block from a bitstream; determining a scanning unit and a scanning order of the current block; and rearranging the transform coefficients of the current block by scanning the same base on the determined scanning unit and scanning order.
1. A method of decoding an image, the method comprising:
determining a scanning unit of a current block; and
arranging transform coefficients of the current block by scanning the transform coefficients of the current block based on the determined scanning unit,
wherein the scanning is performed depends on a scanning order,
wherein the scanning unit is a coefficient group unit determined based on a size of the current block,
wherein the coefficient group unit is one of a plurality of coefficient group units comprised in the current block,
wherein a size of the scanning unit is determined based on the size of the current block,
wherein a size of each of the plurality of the coefficient group units is a first predetermined size representing a square shape in a case that the size of the current block is a second predetermined size representing a non-square shape,
wherein the number of columns of the plurality of the coefficient group units in the current block is greater than 1 in a case that the size of the current block is the second predetermined size representing a non-square shape,
wherein the number of rows of the plurality of the coefficient group units in the current block is greater than 1 in a case that the size of the current block is the second predetermined size representing a non-square shape,
wherein the scanning order comprises a first scanning order among the plurality of the coefficient group units and a second scanning order among transform coefficients of the coefficient group unit,
wherein a scan direction in which coefficient group units on a diagonal line in the current block are scanned and in which transform coefficients on a diagonal line in the coefficient group are scanned is determined based on whether the current block is a transform skip block or not,
wherein the scan direction is a down-left direction in a case that the current block is not a transform skip block, and
wherein the scan direction is an up-right direction in a case that the current block is a transform skip block.
2. The method of claim 1 , wherein the transform coefficients of the current block are one of an input of dequantization, an input of secondary inverse transform, an output of secondary inverse transform and an input of primary inverse transform.
3. The method of claim 2 , wherein the scanning order is a down-left diagonal scanning order when the transform coefficients of the current block are the input of secondary inverse transform.
4. The method of claim 2 , wherein the scanning order is determined as one of a vertical scanning order and a horizontal scanning order based on an intra prediction mode of the current block when the transform coefficients of the current block are the output of secondary inverse transform.
5. The method of claim 1 , wherein the scanning order is the same as a scanning order of a scaling list of the current block.
6. A method of encoding an image, the method comprising:
determining a scanning unit of a current block; and
arranging transform coefficients of the current block by scanning the transform coefficients of the current block based on the determined scanning unit,
wherein the scanning is performed depending on a scanning order,
wherein the scanning unit is a coefficient group unit determined based on a size of the current block,
wherein the coefficient group unit is one of a plurality of coefficient group units comprised in the current block,
wherein a size of the scanning unit is determined based on the size of the current block,
wherein a size of each of the plurality of the coefficient group units is a first predetermined size representing a square shape in a case that the size of the current block is a second predetermined size representing a non-square shape,
wherein the number of columns of the plurality of the coefficient group units in the current block is greater than 1 in a case that the size of the current block is the second predetermined size representing a non-square shape,
wherein the number of rows of the plurality of the coefficient group units in the current block is greater than 1 in a case that the size of the current block is the second predetermined size representing a non-square shape,
wherein the scanning order comprises a first scanning order among the plurality of the coefficient group units and a second scanning order among transform coefficients of the coefficient group unit,
wherein a scan direction in which coefficient group units on a diagonal line in the current block are scanned and in which transform coefficients on a diagonal line in the coefficient group are scanned is determined based on whether the current block is a transform skip block or not,
wherein the scan direction is a down-left direction in a case that the current block is not a transform skip block, and
wherein the scan direction is an up-right direction in a case that the current block is a transform skip block.
7. The method of claim 6 , wherein the transform coefficients of the current block are one of an input of dequantization, an input of secondary inverse transform, an output of secondary inverse transform and an input of primary inverse transform.
8. The method of claim 7 , wherein the scanning order is a down-left diagonal scanning order when the transform coefficients of the current block are the input of secondary inverse transform.
9. The method of claim 7 , wherein the scanning order is determined as one of a vertical scanning order and a horizontal scanning order based on an intra prediction mode of the current block when the transform coefficients of the current block are the output of secondary inverse transform.
10. A non-transitory recording medium storing a bitstream generated by an encoding method, the encoding method including:
determining a scanning unit of a current block; and
arranging transform coefficients of the current block by scanning the transform coefficients of the current block based on the determined scanning unit
wherein the scanning is performed depending on a scanning order,
wherein the scanning unit is a coefficient group unit determined based on a size of the current block, and
wherein the coefficient group unit is one of a plurality of coefficient group units comprised in the current block,
wherein a size of the scanning unit is determined based on the size of the current block,
wherein a size of each of the plurality of the coefficient group units is a first predetermined size representing a square shape in a case that the size of the current block is a second predetermined size representing a non-square shape,
wherein the number of columns of the plurality of the coefficient group units in the current block is greater than 1 in a case that the size of the current block is the second predetermined size representing a non-square shape,
wherein the number of rows of the plurality of the coefficient group units in the current block is greater than 1 in a case that the size of the current block is the second predetermined size representing a non-square shape,
wherein the scanning order comprises a first scanning order among the plurality of the coefficient group units and a second scanning order among transform coefficients of the coefficient group unit,
wherein a scan direction in which coefficient group units on a diagonal line in the current block are scanned and in which transform coefficients on a diagonal line in the coefficient group are scanned is determined based on whether the current block is a transform skip block or not,
wherein the scan direction is a down-left direction in a case that the current block is not a transform skip block, and
wherein the scan direction is an up-right direction in a case that the current block is a transform skip block.
11. The method of claim 1 , wherein the size of the scanning unit is 4×4 in a case that the size of the current block is one of 16×8 and 8×16.
12. The method of claim 6 , wherein the size of the scanning unit is 4×4 in a case that the size of the current block is one of 16×8 and 8×16.
13. The non-transitory recording medium of claim 10 , wherein the size of the scanning unit is 4×4 in a case that the size of the current block is one of 16×8 and 8×16.