Method and system for picture segmentation using columns
Described is picture segmentation through columns and slices in video encoding and decoding. A video picture is divided into a plurality of columns, each column covering only a part of the video picture in a horizontal dimension. All coded tree blocks (“CTBs”) belonging to a slice may belong to one or more columns. The columns may be used to break the same or different prediction or in-loop filtering mechanisms of the video coding, and the CTB scan order used for encoding and/or decoding may be local to a column. Column widths may be indicated in a parameter set and/or may be adjusted at the slice level. At the decoder, column width may be parsed from the bitstream, and slice decoding may occur in one or more columns.
1. A method for encoding in an encoder a bitstream of coded pictures, the method comprising:
receiving an uncoded picture;
encoding, by one or more processors, the uncoded picture into the bitstream as a first coded picture,
wherein the first coded picture comprises a plurality of coded tree blocks (CTBs),
wherein the first coded picture is segmented into at least two columns and at least two slices,
wherein each CTB belongs to both a respective column and a respective slice,
wherein a slice boundary in the first coded picture is not equal to a column boundary in the first coded picture and wherein a first slice of the at least two slices spans multiple columns, and
wherein encoding the uncoded picture is performed using multiple columns and multiple slices, and wherein encoding the uncoded picture comprises:
for a slice of the multiple slices, encoding the CTBs in the slice in an order that is based on the respective columns to which the CTBs in the slice belong, and
breaking in-loop filtering within the first slice at a column boundary between adjacent columns of the multiple columns;
encoding, by the one or more processors and in a first picture parameter set in the bitstream, a value for a number of columns N minus one for the first coded picture of the bitstream; and
encoding, by the one or more processors and in the first picture parameter set in the bitstream, a signal indicating whether the column widths pertaining to leftmost N−1 columns of the first coded picture are equal,
wherein, when the signal indicates that the column widths pertaining to the leftmost N−1 columns of the first coded picture are equal, a column width of the rightmost column of the first coded picture is different from a column width of a leftmost column of the first coded picture.
2. The method of claim 1 , wherein the column width of a rightmost column of the first coded picture is calculated using a width of the first coded picture and the column widths pertaining to the N−1 leftmost columns for the first coded picture.
3. The method of claim 1 , wherein, when the signal indicates that the column widths pertaining to the leftmost N−1 columns are equal, a column width of each of the leftmost N−1 columns of the first coded picture is determined by calculating, based on the first picture parameter set, equal column widths pertaining to the leftmost N−1 columns.
4. The method of claim 3 , wherein the column width of the rightmost column of the first coded picture is different from the column width of each of the leftmost N−1 columns.
5. The method of claim 1 , wherein, when the signal does not indicate that the column widths pertaining to the leftmost N−1 columns are equal, a column width of each of the leftmost N−1 columns of the first coded picture is encoded in the first picture parameter set.
6. An encoder for encoding a bitstream of coded pictures, the encoding comprising:
one or more processors and one or more storage devices storing instructions that are operable, when executed by the one or more processors, to cause the one or more processors to perform operations comprising:
receiving an uncoded picture;
encoding the uncoded picture into the bitstream as a first coded picture,
wherein the first coded picture comprises a plurality of coded tree blocks (CTBs),
wherein the first coded picture is segmented into at least two columns and at least two slices,
wherein each CTB belongs to both a respective column and a respective slice,
wherein a slice boundary in the first coded picture is not equal to a column boundary in the first coded picture and wherein a first slice of the at least two slices spans multiple columns, and
wherein encoding the uncoded picture is performed using multiple columns and multiple slices, and wherein encoding the uncoded picture comprises:
for a slice of the multiple slices, encoding the CTBs in the slice in an order that is based on the respective columns to which the CTBs in the slice belong, and
breaking in-loop filtering within the first slice at a column boundary between adjacent columns of the multiple columns;
encoding, in a first picture parameter set in the bitstream, a value for a number of columns N minus one for the first coded picture of the bitstream; and
encoding, in the first picture parameter set in the bitstream, a signal indicating whether the column widths pertaining to leftmost N−1 columns of the first coded picture are equal,
wherein, when the signal indicates that the column widths pertaining to the leftmost N−1 columns of the first coded picture are equal, a column width of the rightmost column of the first coded picture is different from a column width of a leftmost column of the first coded picture.
7. The encoder of claim 6 , wherein the column width of a rightmost column of the first coded picture is calculated using a width of the first coded picture and the column widths pertaining to the N−1 leftmost columns for the first coded picture.
8. The encoder of claim 6 , wherein, when the signal indicates that the column widths pertaining to the leftmost N−1 columns are equal, a column width of each of the leftmost N−1 columns of the first coded picture is determined by calculating, based on the first picture parameter set, equal column widths pertaining to the leftmost N−1 columns.
9. The encoder of claim 8 , wherein the column width of the rightmost column of the first coded picture is different from the column width of each of the leftmost N−1 columns.
10. The encoder of claim 6 , wherein, when the signal does not indicate that the column widths pertaining to the leftmost N−1 columns are equal, a column width of each of the leftmost N−1 columns of the first coded picture is encoded in the first picture parameter set.
11. A non-transitory computer-readable medium storing instructions that, upon execution by one or more processors, cause the one or more processors to perform operations comprising:
receiving an uncoded picture;
encoding, by one or more processors, the uncoded picture into a bitstream as a first coded picture,
wherein the first coded picture comprises a plurality of coded tree blocks (CTBs),
wherein the first coded picture is segmented into at least two columns and at least two slices,
wherein each CTB belongs to both a respective column and a respective slice,
wherein a slice boundary in the first coded picture is not equal to a column boundary in the first coded picture and wherein a first slice of the at least two slices spans multiple columns, and
wherein encoding the uncoded picture is performed using multiple columns and multiple slices, and wherein encoding the uncoded picture comprises:
for a slice of the multiple slices, encoding the CTBs in the slice in an order that is based on the respective columns to which the CTBs in the slice belong, and
breaking in-loop filtering within the first slice at a column boundary between adjacent columns of the multiple columns;
encoding, by the one or more processors and in a first picture parameter set in the bitstream, a value for a number of columns N minus one for the first coded picture of the bitstream; and
encoding, by the one or more processors and in the first picture parameter set in the bitstream, a signal indicating whether the column widths pertaining to leftmost N−1 columns of the first coded picture are equal,
wherein, when the signal indicates that the column widths pertaining to the leftmost N−1 columns of the first coded picture are equal, a column width of the rightmost column of the first coded picture is different from a column width of a leftmost column of the first coded picture.
12. The computer-readable medium of claim 11 , wherein the column width of a rightmost column of the first coded picture is calculated using a width of the first coded picture and the column widths pertaining to the N−1 leftmost columns for the first coded picture.
13. The computer-readable medium of claim 11 , wherein, when the signal indicates that the column widths pertaining to the leftmost N−1 columns are equal, a column width of each of the leftmost N−1 columns of the first coded picture is determined by calculating, based on the first picture parameter set, equal column widths pertaining to the leftmost N−1 columns.
14. The computer-readable medium of claim 13 , wherein the column width of the rightmost column of the first coded picture is different from the column width of each of the leftmost N−1 columns.
15. The computer-readable medium of claim 11 , wherein, when the signal does not indicate that the column widths pertaining to the leftmost N−1 columns are equal, a column width of each of the leftmost N−1 columns of the first coded picture is encoded in the first picture parameter set.
16. A non-transitory computer-readable medium storing a bitstream generated by the encoding method of claim 1 .