Method and apparatus for intra string copy

1. A method of video decoding for a decoder, the method comprising:

receiving coded information of a block in a coded region from a coded video bitstream, the coded information including signaling information and syntax elements associated with the block, each of the syntax elements including one or more bins, the block including a plurality of strings, and the block being coded by a string matching mode;

determining a threshold value indicating a maximum number of context coded bins associated with the block and a cutoff number, the threshold value being equal to a maximum number of context coded bins that are allowed for another block of a same size coded in equal value string (EVS) mode in which samples in a string of the other block have a same chroma/luma value;

determining whether to decode a first syntax element of the syntax elements in a context coding mode or a by-pass coding mode based on whether a total number of context coded bins in the block before the first syntax element plus the cutoff number is larger than the maximum number of context coded bins associated with the block, wherein the cutoff number includes a first candidate value that is equal to a maximum number of bins that are allowed to be coded by the context coding mode for a second syntax element of the syntax elements when the block is coded in an intra string copy (ISC) mode; and

decoding the first syntax element using the context coding mode or the by-pass coding mode, based on the determination.

2. The method of claim 1 , wherein the first syntax element is coded based on one of (i) the context coding mode in response to the total number of the context coded bins in the block before the first syntax element plus the cutoff number being not larger than the maximum number of context coded bins associated with the block, and (ii) the by-pass coding mode in response to the total number of the context coded bins in the block before the first syntax element plus the cutoff number being larger than the maximum number of context coded bins associated with the block.

3. The method of claim 1 , wherein:

each of the plurality of strings includes one or more samples, and

the string matching mode includes one of (i) the ISC mode configured to reconstruct each of the plurality of the strings in the block based on a respective reference string that is indicated by a string offset vector, and (ii) the EVS mode configured to reconstruct each of the plurality of strings in the block by copying values of a reference string above the corresponding string, or setting values of other samples in the corresponding string with a value of a first sample of the corresponding string.

4. The method of claim 1 , wherein the cutoff number further includes one of:

a second candidate value as a maximum number of bins that are allowed to be coded by the context coding mode for the first syntax element,

a third candidate value as a product of a constant value and an average threshold value signaled in the coded video bitstream, the average threshold value indicating a maximum number of bins that are allowed to be coded by the context coding mode for each sample of the block, the constant value being one of ⅛, 1/10, and 1/16,

a fourth candidate value that is equal to 10 or 20, or

a fifth candidate value as one half of the maximum number of bins that are allowed to be coded by the context coding mode for the second syntax element when the block is coded in the ISC mode.

5. A method of video encoding for an encoder, the method comprising:

receiving syntax elements associated with a block of a region in a picture, the block being coded in a string matching mode, each of the syntax elements including one or more bins, the block including a plurality of strings;

determining a threshold value indicating a maximum number of context coded bins associated with the block and a cutoff number, the threshold value being equal to a maximum number of context coded bins that are allowed for another block of a same size coded in equal value string (EVS) mode in which samples in a string of the other block have a same chroma/luma value;

determining whether to encode a first syntax element of the syntax elements in a context coding mode or a by-pass coding mode based on whether a total number of context coded bins in the block before the first syntax element plus the cutoff number is larger than the maximum number of context coded bins associated with the block, wherein the cutoff number includes a first candidate value that is equal to a maximum number of bins that are allowed to be coded by the context coding mode for a second syntax element of the syntax elements when the block is coded in an intra string copy (ISC) mode; and

coding the first syntax element using the context coding mode or the by-pass coding mode, based on the determination.

6. The method of claim 5 , wherein the first syntax element is coded based on one of (i) the context coding mode in response to the total number of the context coded bins in the block before the first syntax element plus the cutoff number being not larger than the maximum number of context coded bins associated with the block, and (ii) the by-pass coding mode in response to the total number of the context coded bins in the block before the first syntax element plus the cutoff number being larger than the maximum number of context coded bins associated with the block.

7. The method of claim 5 , wherein:

each of the plurality of strings includes one or more samples, and

the string matching mode includes one of (i) the ISC mode configured to reconstruct each of the plurality of the strings in the block based on a respective reference string that is indicated by a string offset vector, and (ii) the EVS mode configured to reconstruct each of the plurality of strings in the block by copying values of a reference string above the corresponding string, or setting values of other samples in the corresponding string with a value of a first sample of the corresponding string.

8. The method of claim 5 , wherein the cutoff number further includes one of:

a second candidate value as a maximum number of bins that are allowed to be coded by the context coding mode for the first syntax element,

a third candidate value as a product of a constant value and an average threshold value that indicates a maximum number of bins that are allowed to be coded by the context coding mode for each sample of the block, the constant value being one of ⅛, 1/10, and 1/16,

a fourth candidate value that is equal to 10 or 20, or

a fifth candidate value as one half of the maximum number of bins that are allowed to be coded by the context coding mode for the second syntax element when the block is coded in the ISC mode.

9. A method of processing visual media data, the method comprising:

performing a conversion between a visual media file and a bitstream of visual media data according to a format rule, wherein:

the bitstream includes coded information of a block in a picture, the coded information including syntax elements associated with the block, each of the syntax elements including one or more bins, the block including a plurality of strings, and the block being coded by a string matching mode;

the format rule specifies that a threshold value is determined to indicate a maximum number of context coded bins associated with the block and a cutoff number, the threshold value being equal to a maximum number of context coded bins that are allowed for another block of a same size coded in equal value string (EVS) mode in which samples in a string of the other block have a same chroma/luma value;

the format rule specifies whether a first syntax element of the syntax elements is coded in a context coding mode or a by-pass coding mode is determined based on whether a total number of context coded bins in the block before the first syntax element plus the cutoff number is larger than the maximum number of context coded bins associated with the block, wherein the cutoff number includes a first candidate value that is equal to a maximum number of bins that are allowed to be coded by the context coding mode for a second syntax element of the syntax elements when the block is coded in an intra string copy (ISC) mode; and

the format rule specifies that the first syntax element is coded using the context coding mode or the by-pass coding mode, based on the determination.

10. The method of claim 9 , wherein the first syntax element is coded based on one of (i) the context coding mode in response to the total number of the context coded bins in the block before the first syntax element plus the cutoff number being not larger than the maximum number of context coded bins associated with the block, and (ii) the by-pass coding mode in response to the total number of the context coded bins in the block before the first syntax element plus the cutoff number being larger than the maximum number of context coded bins associated with the block.

11. The method of claim 9 , wherein:

each of the plurality of strings includes one or more samples, and

the string matching mode includes one of (i) the ISC mode configured to reconstruct each of the plurality of the strings in the block based on a respective reference string that is indicated by a string offset vector, and (ii) the EVS mode configured to reconstruct each of the plurality of strings in the block by copying values of a reference string above the corresponding string, or setting values of other samples in the corresponding string with a value of a first sample of the corresponding string.

12. The method of claim 9 , wherein the cutoff number further includes one of:

a second candidate value as a maximum number of bins that are allowed to be coded by the context coding mode for the first syntax element,

a third candidate value as a product of a constant value and an average threshold value signaled in the bitstream, the average threshold value indicating a maximum number of bins that are allowed to be coded by the context coding mode for each sample of the block, the constant value being one of ⅛, 1/10, and 1/16,

a fourth candidate value that is equal to 10 or 20, or

a fifth candidate value as one half of the maximum number of bins that are allowed to be coded by the context coding mode for the second syntax element when the block is coded in the ISC mode.