Apparatuses for encoding and decoding image, and methods for encoding and decoding image thereby
An image decoding method may include: obtaining, from a sequence parameter set of a bitstream, information indicating a plurality of first reference image lists for an image sequence including a current image; obtaining, from a group header of the bitstream, an indicator for a current block group including a current block in the current image; obtaining a second reference image list by modifying a first reference image list indicated by the indicator, from among the plurality of first reference image lists, into the second reference image list; and prediction-decoding a lower block of the current block based on a second reference image included in the second reference image list.
1. An image decoding method comprising:
obtaining, from a sequence parameter set of a bitstream, information about a plurality of first reference picture lists for a picture sequence including a current picture;
obtaining, from a slice header of the bitstream, an indicator for a current slice in the current picture;
if a first reference picture list indicated by the indicator among the plurality of first reference picture lists does not include a picture order count (POC)-related information about a long-term type reference picture, obtaining the POC-related information about the long-term type reference picture from the slice header of the bitstream;
constituting a second reference picture list by using the POC-related information about the long-term type reference picture and a POC-related information about a short-term type reference picture included in the first reference picture list indicated by the indicator;
obtaining a predicted sample of a current sample included in the current picture based on a reference picture included in the second reference picture list;
obtaining information indicating a post-processing parameter set from among a plurality of post-processing parameter sets, the post-processing parameter set being applied to luma mapping for the current picture;
obtaining one or more luma mapping parameters from the post-processing parameter set of the bitstream, the post-processing parameter set being different from the sequence parameter set;
obtaining a modified predicted sample by changing the predicted sample based on the one or more luma mapping parameters obtained from the post-processing parameter set; and
obtaining a reconstructed sample of the current sample included the current picture based on the modified predicted sample.
2. An image decoding apparatus comprising:
a processor is configured to:
obtain, from a sequence parameter set of a bitstream, information about a plurality of first reference picture lists for a picture sequence including a current picture;
obtain, from a slice header of the bitstream, an indicator for a current slice in the current picture;
if a first reference picture list indicated by the indicator among the plurality of first reference picture lists does not include a picture order count (POC)-related information about a long-term type reference picture, obtain the POC-related information about the long-term type reference picture from the slice header of the bitstream;
constitute a second reference picture list by using the POC-related information about the long-term type reference picture and a POC-related information about a short-term type reference picture included in the first reference picture list indicated by the indicator;
obtain a predicted sample of a current sample included in the current picture based on a reference picture included in the second reference picture list,
obtain information indicating a post-processing parameter set from among a plurality of post-processing parameter sets, the post-processing parameter set being applied to luma mapping for the current picture;
obtain one or more luma mapping parameters from the post-processing parameter set of the bitstream, the post-processing parameter set being different from the sequence parameter set;
obtain a modified predicted sample by changing the predicted sample based on the one or more luma mapping parameters obtained from the post-processing parameter set; and
obtain a reconstructed sample of the current sample included the current picture based on the modified predicted sample.
3. An image encoding method comprising:
determining a plurality of first reference picture lists for a picture sequence including a current picture;
selecting, from among the plurality of first reference picture lists, a first reference picture list for a current slice in the current picture;
if the selected first reference picture list among the plurality of first reference picture lists does not include a picture order count (POC)-related information about a long-term type reference picture, determining the POC-related information about the long-term type reference picture;
constituting a second reference picture list by using the POC-related information about the long-term type reference picture and a POC-related information about a short-term type reference picture included in the selected first reference picture list; and
obtaining a predicted sample of a current sample included in the current picture based on a reference picture included in the second reference picture list;
selecting a post-processing parameter set from among a plurality of post-processing parameter sets, the post-processing parameter set being applied to luma mapping for the current picture;
identifying one or more luma mapping parameters corresponding to the post-processing parameter set, the post-processing parameter set being different from the sequence parameter set;
encoding information about the plurality of first reference picture lists for the picture sequence including the current picture, an indicator for the current slice in the current picture, the POC-related information about the long-term type reference picture, and the one or more luma mapping parameters; and
generating a bitstream including the encoded information, the encoded indicator, the encoded POC-related information, and the encoded one or more luma mapping parameters.
4. A method for transmitting a bitstream, the method comprising:
determining a plurality of first reference picture lists for a picture sequence including a current picture;
selecting, from among the plurality of first reference picture lists, a first reference picture list for a current slice in the current picture;
if the selected first reference picture list among the plurality of first reference picture lists does not include a picture order count (POC)-related information about a long-term type reference picture, determining the POC-related information about the long-term type reference picture;
constituting a second reference picture list by using the POC-related information about the long-term type reference picture and a POC-related information about a short-term type reference picture included in the selected first reference picture list; and
obtaining a predicted sample of a current sample included in the current picture based on a reference picture included in the second reference picture list;
selecting a post-processing parameter set from among a plurality of post-processing parameter sets, the post-processing parameter set being applied to luma mapping for the current picture;
identifying one or more luma mapping parameters corresponding to the post-processing parameter set, the post-processing parameter set is different from the sequence parameter set;
encoding information about the plurality of first reference picture lists for the picture sequence including the current picture, an indicator for the current slice in the current picture, the POC-related information about the long-term type reference picture, and the one or more luma mapping parameters;
generating the bitstream including the encoded information, the encoded indicator, the encoded POC-related information, and the encoded one or more luma mapping parameters; and
transmitting the bitstream from an image encoding apparatus to an image decoding apparatus.