Method for alignment across layers in coded video stream
A method, computer program, and computer system is provided for aligning across layers in a coded video stream. A video bitstream having multiple layers is decoded. One or more subpicture regions are identified from among the multiple layers of the decoded video bitstream, the subpicture regions including a background region and one or more foreground subpicture regions. An enhanced subpicture is decoded and displayed based on a determination that a foreground subpicture region is selected. The background region is decoded and displayed based on a determination that a foreground subpicture region was not selected.
1. A method of aligning across layers in a coded video stream, executable by a processor, comprising:
receiving a video bitstream having multiple layers;
identifying one or more subpictures that are independently decodable from among the multiple layers of the video bitstream based on one or more picture order count values within an access unit associated with respective subpictures among the one or more subpictures, wherein the access unit includes a plurality of subpictures with two or more picture order count values, wherein the one or more picture order count values are used to determine respective access unit count values for the one or more subpictures, and wherein the respective access unit count values indicate a distinct composition time instance for the one or more subpictures;
decoding the one or more subpictures; and
aligning the one or more subpictures across the multiple layers.
2. The method of claim 1 , wherein the respective access unit count values are determined based on a division of the one or more picture order count values by an integer value.
3. The method of claim 1 , wherein the respective access unit count values are determined based on a shift operation on the one or more picture order count values.
4. The method of claim 1 , wherein a picture cycle count value indicates a maximum number of picture order count values within a same access unit.
5. The method of claim 4 , wherein the picture cycle count value is determined based a number of spatial layers in the video bitstream.
6. The method of claim 1 , wherein the one or more subpictures within a same access unit have a same TemporalID.
7. The method of claim 1 , wherein the one or more subpictures within a same access unit have different spatial layer identifier.
8. The method of claim 1 , wherein motion vector scaling within the access unit based on the one or more picture order count values is disabled for temporal motion vector prediction of a current subpicture among the one or more subpictures.
9. The method of claim 8 , wherein the motion vector scaling within the access unit is based on a spatial resolution ratio between a spatial resolution of a reference picture and the spatial resolution of the current subpicture.
10. A computer system for aligning across layers in a coded video stream, the computer system comprising:
one or more computer-readable non-transitory storage media configured to store computer program code; and
one or more computer processors configured to access said computer program code and operate as instructed by said computer program code, said computer program code including:
receiving code configured to cause the one or more computer processors to receive a video bitstream having multiple layers;
identifying code configured to cause the one or more computer processors to identify one or more subpictures that are independently decodable from among the multiple layers of the video bitstream based on one or more picture order count values within an access unit associated with respective subpictures among the one or more subpictures, wherein the access unit includes a plurality of subpictures with two or more picture order count values, wherein the one or more picture order count values are used to determine respective access unit count values for the one or more subpictures, and wherein the respective access unit count values indicate a distinct composition time instance for the one or more subpictures;
first decoding code configured to cause the one or more computer processors to decode the one or more subpictures; and
aligning code configured to cause the one or more computer processors to align the one or more subpictures across the multiple layers.
11. The computer system of claim 10 , wherein the respective access unit count values are determined based on a division of the one or more picture order count values by an integer value.
12. The computer system of claim 10 , wherein the respective access unit count values are determined based on a shift operation on the one or more picture order count values.
13. The computer system of claim 10 , wherein a picture cycle count value indicates a maximum number of picture order count values within a same access unit.
14. The computer system of claim 13 , wherein the picture cycle count value is determined based a number of spatial layers in the video bitstream.
15. The computer system of claim 10 , wherein the one or more subpictures within a same access unit have a same TemporalID.
16. The computer system of claim 10 , wherein motion vector scaling within the access unit based on the one or more picture order count values is disabled for temporal motion vector prediction of a current subpicture among the one or more subpictures.
17. The computer system of claim 16 , wherein the motion vector scaling within the access unit is based on a spatial resolution ratio between a spatial resolution of a reference picture and the spatial resolution of the current subpicture.
18. A non-transitory computer readable medium having stored thereon a computer program for aligning across layers in a coded video stream, the computer program configured to cause one or more computer processors to: receive a video bitstream having multiple la yers; identify one or more subpictures that are independently decodable from among the multiple layers of the video bitstream based on one or more picture order count values within an access unit associated with respective subpictures among the one or more subpictures, wherein the access unit includes a plurality of subpictures with two or more picture order count values, wherein the one or more picture order count values are used to determine respective access unit count values for the one or more subpictures, and wherein the respective access unit count values indicate a distinct composition time instance for the one or more subpictures; decode the one or more subpictures; and align the one or more subpictures across the multiple layers.