Video coding and decoding

A method of decoding a sequence of encoded images, comprising:

• receiving a bitstream having a series of picture units, each said picture unit corresponding to one encoded image and including one or more network abstraction layer (NAL) units, the NAL units includable in the series of picture units comprising video coding layer (VCL) NAL units which each contain encoded image data and also comprising adaptation parameter set (APS) NAL units which each contain an adaptation parameter set (APS) having parameters for performing one or more types of processing operation on the image data contained in one or more VCL NAL units, and the APS NAL units includable in the series of picture units comprising a prefix APS NAL unit and a suffix APS NAL unit,
• wherein if a prefix APS NAL unit is present in a picture unit, said prefix APS NAL unit shall precede a first VCL NAL unit of the picture unit concerned, and if a suffix APS NAL unit is present in a picture unit, said suffix APS NAL unit shall follow a last VCL NAL unit of the picture unit concerned, each said APS NAL unit having an APS type and an APS identifier,
• wherein all APS NAL units with a prefix NAL unit type and a particular APS identifier and a particular APS type within a given picture unit have the same contents, and all APS NAL units with a suffix NAL unit type and a particular APS identifier and a particular APS type within a given picture unit have the same contents,
• wherein inclusion, in the same picture unit, of a prefix APS NAL unit and a suffix APS NAL unit having the same APS type and the same APS identifier but different contents is permitted, and
• wherein an APS NAL unit in the bitstream is capable of including parameters for Luma mapping with chroma scaling (LMCS).

A device for encoding a sequence of images in a bitstream, comprising:

• one or more processors that execute a program comprising instructions that cause, when executed by the one or more processors, the one or more processors to:
• provide a series of picture units in the bitstream, each said picture unit corresponding to one encoded image and including one or more network abstraction layer (NAL) units, the NAL units includable in the series of picture units comprising video coding layer (VCL) NAL units which each contain encoded image data and also comprising adaptation parameter set (APS) NAL units which each contain an adaptation parameter set (APS) having parameters for performing one or more types of processing operation on the image data contained in one or more VCL NAL units, and the APS NAL units includable in the series of picture units comprising a prefix APS NAL unit and a suffix APS NAL unit,
• wherein if a prefix APS NAL unit is present in a picture unit, said prefix APS NAL unit shall precede a first VCL NAL unit of the picture unit concerned, and if a suffix APS NAL unit is present in a picture unit, said suffix APS NAL unit shall follow a last VCL NAL unit of the picture unit concerned, each said APS NAL unit having an APS type and an APS identifier,
• wherein all APS NAL units with a prefix NAL unit type and a particular APS identifier and a particular APS type within a given picture unit have the same contents, and all APS NAL units with a suffix NAL unit type and a particular APS identifier and a particular APS type within a given picture unit have the same contents, and
• wherein inclusion, in the same picture unit, of a prefix APS NAL unit and a suffix APS NAL unit having the same APS type and the same APS identifier but different contents is permitted, and
• wherein an APS NAL unit in the bitstream is capable of including parameters for Luma mapping with chroma scaling (LMCS).

A device for decoding a sequence of encoded images, comprising:

• one or more processors that execute a program comprising instructions that cause, when executed by the one or more processors, the one or more processors to:
• receive a bitstream having a series of picture units, each said picture unit corresponding to one encoded image and including one or more network abstraction layer (NAL) units, the NAL units includable in the series of picture units comprising video coding layer (VCL) NAL units which each contain encoded image data and also comprising adaptation parameter set (APS) NAL units which each contain an adaptation parameter set (APS) having parameters for performing one or more types of processing operation on the image data contained in one or more VCL NAL units, and the APS NAL units includable in the series of picture units comprising a prefix APS NAL unit and a suffix APS NAL unit,
• wherein if a prefix APS NAL unit is present in a picture unit, said prefix APS NAL unit shall precede a first VCL NAL unit of the picture unit concerned, and if a suffix APS NAL unit is present in a picture unit, said suffix APS NAL unit shall follow a last VCL NAL unit of the picture unit concerned, each said APS NAL unit having an APS type and an APS identifier,
• wherein all APS NAL units with a prefix NAL unit type and a particular APS identifier and a particular APS type within a given picture unit have the same contents, and all APS NAL units with a suffix NAL unit type and a particular APS identifier and a particular APS type within a given picture unit have the same contents,
• wherein inclusion, in the same picture unit, of a prefix APS NAL unit and a suffix APS NAL unit having the same APS type and the same APS identifier but different contents is permitted, and
• wherein an APS NAL unit in the bitstream is capable of including parameters for Luma mapping with chroma scaling (LMCS).