Multi-layer video encoding method and apparatus, and multi-layer video decoding method and apparatus

A multilayer video decoding apparatus comprising at least one Decoded Picture Buffer (DPB) and at least one processor, wherein the at least one processor is configured to:

• obtain, from a video parameter set network abstraction layer (VPS NAL) unit comprised in a bitstream, picture type alignment information indicating whether all pictures comprised in a same access unit have a same picture type,
• based on a value of the picture type alignment information being 0, obtain, from the VPS NAL unit, intra random access point (IRAP) alignment information indicating whether all pictures referring to an IRAP picture have a same picture type as the IRAP picture,
• based on a value of the IRAP alignment information being 1, obtain, from the VPS NAL unit, instantaneous decoder refresh (IDR) alignment information indicating that all pictures in the same access unit are IDR pictures when at least one picture of the same access unit is an IRAP picture for each access unit referring to the VPS NAL unit, and
• reconstruct a multilayer video by decoding encoded data by using the IDR alignment information,
• wherein the at least one processor is further configured to:
• based on a value of the IDR alignment information being 1 and at least one picture of the same access unit is the IRAP picture, reconstruct a multilayer video, by determining to not read, from the bitstream, picture order count (POC) information regarding the pictures in the same access unit initializing POC of a decoded picture buffer (DPB), and decoding the pictures in the same access unit without using POC.

A multilayer video encoding method that is implemented by at least one processor, the multilayer video encoding method comprising:

• generating base layer encoded data and enhancement layer encoded data by encoding an input image;
• generating picture type alignment information indicating whether all pictures comprised in a same access unit have a same picture type,
• based on a value of the picture type alignment information being 0, generating intra random access point (IRAP) alignment information indicating whether all pictures referring to an IRAP picture have a same picture type as the IRAP picture, and
• based on a value of the IRAP alignment information being 1, generating instantaneous decoder refresh (IDR) alignment information indicating whether all pictures in the same access unit are IDR pictures when at least one picture of the same access unit is an IRAP picture;
• and
• generating a network abstraction layer (NAL) unit comprising the generated picture type alignment information, the generated IRAP alignment information, and the generated instantaneous decoder refresh (IDR) alignment information;
• and
• generating a bitstream comprising the NAL unit,
• wherein the generating of the base layer encoded data and the enhancement layer encoded data comprises setting all of corresponding pictures of other layers as IDR pictures, when a picture of any layer included in the same access unit is an IDR picture,
• wherein the NAL unit is a video parameter set network abstraction layer (VPS NAL) unit, and
• wherein the picture type alignment information, the IRAP alignment information, and the IDR alignment information are commonly used in decoding the base layer encoded data and the enhancement layer encoded data.