Method and apparatus for employing dynamic range mapping information for HDR image decoder considering backward compatibility

1 . A method of decoding an image performed by an image decoding apparatus, the method comprising:

analyzing an image characteristic of a current image by using one or more pixels of a current block and one or more pixels of a neighboring block;

determining mapping information based on the analyzed image characteristic; and

decoding the current image based on the mapping information,

wherein the mapping information is determined for at least one of a plurality of intervals, the plurality of intervals being obtained by dividing a luminance range for the current image,

wherein the determining of the mapping information comprises modifying, based on the analyzed image characteristic, the mapping information using modification information corresponding to an interval of the current image,

wherein the interval of the current image is representative of one of the plurality of intervals,

wherein the modification of the mapping information is performed based on a flag transmitted from an image encoding apparatus,

wherein the image decoding apparatus receives a bitstream from the image encoding apparatus,

wherein the bitstream includes a picture parameter set (PPS), a sequence parameter set (SPS) and a video parameter set (VPS),

wherein the modification information is included in the sequence parameter set of the bitstream,

wherein the modification information is received, from the bitstream, for each of the plurality of intervals, and

wherein the modification information comprises information on a position of the interval and a modification value needed for the modification.

2 . A method of encoding an image performed by an image encoding apparatus, the method comprising:

analyzing an image characteristic of a current image by using one or more pixels of a current block and one or more pixels of a neighboring block;

determining mapping information based on the analyzed image characteristic; and

encoding the current image based on the mapping information,

wherein the mapping information is determined for at least one of a plurality of intervals, the plurality of intervals being obtained by dividing a luminance range for the current image,

wherein the determining of the mapping information comprises modifying, based on the analyzed image characteristic, the mapping information using modification information corresponding to an interval of the current image,

wherein the interval of the current image is representative of one of the plurality of intervals,

wherein a flag indicating whether to perform the modification of the mapping information is encoded by the image encoding apparatus,

wherein the image encoding apparatus transmits a bitstream to an image decoding apparatus,

wherein the bitstream includes a picture parameter set (PPS), a sequence parameter set (SPS) and a video parameter set (VPS),

wherein the modification information is encoded into the sequence parameter set of the bitstream,

wherein the modification information is encoded for each of the plurality of intervals, and

wherein the modification information comprises information on a position of the interval and a modification value needed for the modification.

3 . A non-transitory computer-readable recording medium for storing data associated with a video signal, comprising:

a bitstream stored in the non-transitory computer-readable recording medium, the bitstream comprising a flag indicating whether to perform a modification of mapping information,

wherein the mapping information is a basis for decoding a current image,

wherein an image characteristic of the current image is analyzed by using one or more pixels of a current block and one or more pixels of a neighboring block,

wherein, based on the analyzed image characteristic of the current image, the mapping information is determined for at least one of a plurality of intervals,

wherein the plurality of intervals are obtained by dividing a luminance range for the current image,

wherein the mapping information is determined by modifying, based on the analyzed image characteristic, the mapping information using modification information corresponding to an interval of the current image,

wherein the interval of the current image is representative of one of the plurality of intervals,

wherein the bitstream includes a picture parameter set (PPS), a sequence parameter set (SPS) and a video parameter set (VPS),

wherein the modification information is included in the sequence parameter set of the bitstream,

wherein the modification information for each of the plurality of intervals is included in the bitstream, and

wherein the modification information comprises information on a position of the interval and a modification value needed for the modification.

4 . A method of transmitting a bitstream generated by encoding an image using an encoding method performed by an image encoding apparatus, the encoding method comprising:

analyzing an image characteristic of a current image by using one or more pixels of a current block and one or more pixels of a neighboring block;

determining mapping information based on the analyzed image characteristic; and

encoding the current image based on the mapping information,

wherein the mapping information is determined for at least one of a plurality of intervals, the plurality of intervals being obtained by dividing a luminance range for the current image,

wherein the determining of the mapping information comprises modifying, based on the analyzed image characteristic, the mapping information using modification information corresponding to an interval of the current image,

wherein the interval of the current image is representative of one of the plurality of intervals,

wherein a flag indicating whether to perform the modification of the mapping information is encoded by the image encoding apparatus,

wherein the bitstream includes a picture parameter set (PPS), a sequence parameter set (SPS) and a video parameter set (VPS),

wherein the modification information is encoded into the sequence parameter set of the bitstream,

wherein the modification information is encoded for each of the plurality of intervals, and

wherein the modification information comprises information on a position of the interval and a modification value needed for the modification.