J oint Video Experts Team (jvet) of itu-t sg 6 wp and iso/iec jtc 1/sc 29/wg 11

Partitioning

1. Partitioning of the picture into CTUs

Pictures are divided into a sequence of coding tree units (CTUs). The CTU concept is same to that of the HEVC [6][7]. For a picture that has three sample arrays, a CTU consists of an N×N block of luma samples together with two corresponding blocks of chroma samples.Figure 2 shows the example of a picture divided into CTUs.
The maximum allowed size of the luma block in a CTU is specified to be 128×128 (although the maximum size of the luma transform blocks is 64×64).

Figure 2 – Example of a picture divided into CTUs

2. Partitioning of pictures into subpictures, slices, tiles

A picture is divided into one or more tile rows and one or more tile columns. A tile is a sequence of CTUs that covers a rectangular region of a picture.
A slice consists of an integer number of complete tiles or an integer number of consecutive complete CTU rows within a tile of a picture.
Two modes of slices are supported, namely the raster-scan slice mode and the rectangular slice mode. In the raster-scan slice mode, a slice contains a sequence of complete tiles in a tile raster scan of a picture. In the rectangular slice mode, a slice contains either a number of complete tiles that collectively form a rectangular region of the picture or a number of consecutive complete CTU rows of one tile that collectively form a rectangular region of the picture. Tiles within a rectangular slice are scanned in tile raster scan order within the rectangular region corresponding to that slice.
A subpicture contains one or more slices that collectively cover a rectangular region of a picture.
Figure 3 shows an example of raster-scan slice partitioning of a picture, where the picture is divided into 12 tiles and 3 raster-scan slices.

Figure 3 – Example of a picture partitioned into tiles and reaster-scan slices
Figure 4 shows an example of rectangular slice partitioning of a picture, where the picture is divided into 24 tiles (6 tile columns and 4 tile rows) and 9 rectangular slices.

Figure 4 – Example of a picture partitioned into tiles and rectangular slices
Figure 5Error: Reference source not found shows an example of a picture partitioned into tiles and rectangular slices, where the picture is divided into 4 tiles (2 tile columns and 2 tile rows) and 4 rectangular slices.

Figure 5 – Example of a picture partitioned into 4 tiles and 4 rectangular slices
Figure 6 shows an example of subpicture partitioning of a picture, where a picture is partitioned into 18 tiles, 12 on the left-hand side each covering one slice of 4 by 4 CTUs and 6 tiles on the right-hand side each covering 2 vertically-stacked slices of 2 by 2 CTUs, altogether resulting in 24 slices and 24 subpictures of varying dimensions (each slice is a subpicture).

Figure 6 – Example of a picture partitioned into 28 subpictures

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