Apparatus, a method and a computer program for video coding and decoding

A method comprising:

• encoding, into a parameter set in or along a bitstream, information on a mapping of video coding layer network abstraction layer units, in decoding order, to sub-pictures or sub-picture sequences, wherein the information on the mapping comprises a mapping as a list of sub-picture sequence identifiers for the video coding layer network abstraction layer units, in decoding order, included in an access unit associated with the mapping;
• encoding data of a first sub-picture, wherein the first sub-picture belongs to a first picture, and wherein the first sub-picture belongs to a first sub-picture sequence;
• encoding data of a second sub-picture, wherein the second sub-picture belongs to the first picture, and wherein the second sub-picture belongs to a second sub-picture sequence, the encoding of the data of the second sub-picture being independent of the encoding of the data of the first sub-picture;
• and
• encoding data of a third sub-picture, wherein the third sub-picture belongs to a second picture, wherein the third sub-picture belongs to the first sub-picture sequence, and wherein the encoding comprises using the first sub-picture as a reference for prediction.

An apparatus comprising:

• at least one processor, and
• at least one non-transitory memory including computer program code, the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus to perform at least the following:
• decode, from a parameter set in or along a bitstream, information on a mapping of video coding layer network abstraction layer units, in decoding order, to sub-pictures or sub-picture sequences, wherein the information on the mapping comprises a mapping as a list of sub-picture sequence identifiers for the video coding layer network abstraction layer units, in decoding order, included in an access unit associated with the mapping;
• decode coded data of a first sub-picture belonging to a first picture, and wherein the first sub-picture belongs to a first sub-picture sequence;
• decode coded data of a second sub-picture belonging to the first picture, and wherein the second sub-picture belongs to a second sub-picture sequence, the decoding being independent of the decoding of the coded data of the first sub-picture;
• decode coded data of a third sub-picture, wherein the third sub-picture belongs to a second picture, wherein the third sub-picture belongs to the first sub-picture sequence, wherein the decoding comprises using the first sub-picture as a reference for prediction;
• decode picture composition data separately from decoding the coded data of the first and the second sub-pictures;
• and
• compose a first decoded picture on the basis of the picture composition data, comprising positioning the first sub-picture and the second sub-picture onto the first decoded picture.

An apparatus comprising:

• at least one processor, and
• at least one non-transitory memory including computer program code, the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus to perform at least the following:
• encode, into a parameter set in or along a bitstream, information on a mapping of video coding layer network abstraction layer units, in decoding order, to sub-pictures or sub-picture sequences, wherein the information on the mapping comprises a mapping as a list of sub-picture sequence identifiers for the video coding layer network abstraction layer units, in decoding order, included in an access unit associated with the mapping;
• encode data of a first sub-picture, wherein the first sub-picture belongs to a first picture, and wherein the first sub-picture belongs to a first sub-picture sequence;
• encode data of a second sub-picture, wherein the second sub-picture belongs to the first picture, and wherein the second sub-picture belongs to a second sub-picture sequence, and wherein the encoding is independent of the encoding of the data of the first sub-picture;
• and
• encode data of a third sub-picture, wherein the third sub-picture belongs to a second picture, wherein the third sub-picture belongs to the first sub-picture sequence, and wherein the encoding comprises using the first sub-picture as a reference for prediction.