Abstract: A video processing method includes determining, for a conversion between a block of a video and a bitstream representation of the video, that a secondary transform with a reduced dimension dimension (e.g., an inverse low frequency non-separable transform) is applicable to a single sub-block of the block in case a dimension of the block satisfies a condition. The secondary transform is performed between a forward primary transform and a quantization step or between a de-quantization step and an inverse primary transform. The reduced dimension is reduced from a dimension of the block. The method also includes performing the conversion based on the determining.

Abstract: A method of visual media processing includes determining a size of a buffer to store reference samples for prediction in an intra block copy mode; and performing a conversion between a current video block of visual media data and a bitstream of the current video block, using the reference samples stored in the buffer, wherein the conversion is performed in the intra block copy mode which is based on motion information related to a reconstructed block located in same video region with the current video block without referring to a reference picture.

Abstract: One example method of video processing includes implementing, by a processor, a decoder-side motion vector derivation (DMVD) scheme for motion vector refinement during a conversion between a current video block and a bitstream representation of the current video block by deriving parameters based on a deriving rule. The conversion may include compressing the current video block into the bitstream representation or uncompressing the bitstream representation into pixel values of the current video block.

Abstract: An example method of video processing includes determining, for a conversion between a current block of a video and a bitstream representation of the video, whether to enable usage of a chroma quantization parameter (QP) offset for the current block according to a syntax element at a level of a video unit. The video unit includes the current block and a second block of the video. The method also includes performing the conversion based on the determining.

Abstract: A method of video processing is provided. The method includes: determining, for a conversion between a current video unit of a video and a coded representation of the video, that applicability of a first coding tool and a second coding tool is mutually exclusive; and performing the conversion based on the determining, wherein the first coding tool corresponds to an adaptive color space transformation (ACT) tool; wherein use of the ACT tool comprises: converting, during encoding, a representation of a visual signal from a first color domain to a second color domain, or converting, during decoding, a representation of a visual signal from the second color domain to the first color domain.

Abstract: Video coding and decoding methods are described. An example method includes performing a conversion between a current video block of a video and a bitstream representation of the current video block by determining a first intra coding mode to be stored which is associated with the current video block using a differential coding mode, where the first intra coding mode associated with the current video block is determined according to a second prediction mode used by the differential coding mode, and where, in the differential coding mode, a difference between a quantized residual of an intra prediction of the current video block and a prediction of the quantized residual is represented in the bitstream representation for the current video block using a differential pulse coding modulation (DPCM) representation.

Abstract: A method for visual media processing, including: computing, during a conversion between a current video block of visual media data and a bitstream representation of the current video block, a cross-component linear model (CCLM) and/or a chroma residual scaling (CRS) factor for the current video block based, at least in part, on neighboring samples of a corresponding luma block which covers a top-left sample of a collocated luma block associated with the current video block, wherein one or more characteristics of the current video block are used for identifying the corresponding luma block.

Abstract: A method for processing a video includes performing a conversion between a current block of visual media data and a corresponding coded representation of the visual media data. The conversion of the current block includes determining whether a use of one or both of a bi-directional optical flow (BIO) technique or a decoder-side motion vector refinement (DMVR) technique to the current block is enabled or disabled. Determining the use of the BIO technique or the DMVR technique is based on a cost criterion associated with the current block.

Abstract: A method of video processing includes performing a conversion between a video including a video region and a bitstream of the video according to a rule. The rule specifies a relationship between enablement of a palette mode and a coding type of the video region. The video region may represent a coding block of the video.

Abstract: Innovations in intra block copy (“BC”) prediction mode facilitate intra BC prediction that is more effective in terms of rate-distortion performance and/or computational efficiency of encoding and decoding. For example, some of the innovations provide ways to select block vector (“BV”) values more effectively. Other innovations provide ways to encode/decode BV values more efficiently. Still other innovations address how to perform in-loop deblock filtering when a block has intra BC prediction mode, or address how to perform intra BC prediction when constrained intra prediction is enabled.

Abstract: Innovations in intra block copy (“BC”) prediction mode facilitate intra BC prediction that is more effective in terms of rate-distortion performance and/or computational efficiency of encoding and decoding. For example, some of the innovations provide ways to select block vector (“BV”) values more effectively. Other innovations provide ways to encode/decode BV values more efficiently. Still other innovations address how to perform in-loop deblock filtering when a block has intra BC prediction mode, or address how to perform intra BC prediction when constrained intra prediction is enabled.

Abstract: Innovations in encoding or decoding when switching color spaces are presented. For example, some of the innovations relate to signaling of control information for adaptive color space transformation (“ACT”). Other innovations relate to ACT operations. These innovations can improve coding efficiency when switching between color spaces during encoding and decoding.

Abstract: Approaches to robust encoding and decoding of escape-coded pixels in a palette mode are described. For example, sample values of escape-coded pixels in palette mode are encoded/decoded using a binarization process that depends on a constant value of quantization parameter (“QP”) for the sample values. Or, as another example, sample values of escape-coded pixels in palette mode are encoded/decoded using a binarization process that depends on sample depth for the sample values. Or, as still another example, sample values of escape-coded pixels in palette mode are encoded/decoding using a binarization process that depends on some other fixed rule. In example implementations, these approaches avoid dependencies on unit-level QP values when parsing the sample values of escape-coded pixels, which can make encoding/decoding more robust to data loss.

Abstract: Approaches to robust encoding and decoding of escape-coded pixels in a palette mode are described. For example, sample values of escape-coded pixels in palette mode are encoded/decoded using a binarization process that depends on a constant value of quantization parameter (“QP”) for the sample values. Or, as another example, sample values of escape-coded pixels in palette mode are encoded/decoded using a binarization process that depends on sample depth for the sample values. Or, as still another example, sample values of escape-coded pixels in palette mode are encoded/decoding using a binarization process that depends on some other fixed rule. In example implementations, these approaches avoid dependencies on unit-level QP values when parsing the sample values of escape-coded pixels, which can make encoding/decoding more robust to data loss.

Abstract: Innovations in encoding or decoding when switching color spaces are presented. For example, some of the innovations relate to signaling of control information for adaptive color space transformation (“ACT”). Other innovations relate to ACT operations. These innovations can improve coding efficiency when switching between color spaces during encoding and decoding.

Abstract: Innovations in intra block copy (“BC”) prediction mode facilitate intra BC prediction that is more effective in terms of rate-distortion performance and/or computational efficiency of encoding and decoding. For example, some of the innovations provide ways to select block vector (“BV”) values more effectively. Other innovations provide ways to encode/decode BV values more efficiently. Still other innovations address how to perform in-loop deblock filtering when a block has intra BC prediction mode, or address how to perform intra BC prediction when constrained intra prediction is enabled.

Abstract: Innovations in encoding or decoding when switching color spaces are presented. For example, some of the innovations relate to signaling of control information for adaptive color space transformation (“ACT”). Other innovations relate to ACT operations. These innovations can improve coding efficiency when switching between color spaces during encoding and decoding.

Abstract: Innovations in the area of prediction of block vector (“BV”) values improve encoding or decoding of blocks using intra block copy (“BC”) prediction. For example, some of the innovations relate to use of a default BV predictor with a non-zero value. Other innovations relate to use of a selected one of multiple BV predictor candidates for a current block. Still other innovations relate to use of a skip mode in which a current intra-BC-predicted block uses a predicted BV value.

Abstract: Innovations in the use of base color index map (“BCIM”) mode during encoding and/or decoding simplify implementation by reducing the number of modifications made to support BCIM mode and/or improve coding efficiency of BCIM mode. For example, some of the innovations involve reuse of a syntax structure that is adapted for transform coefficients to instead signal data for elements of an index map in BCIM mode. Other innovations relate to mapping of index values in BCIM mode or prediction of elements of an index map in BCIM mode. Still other innovations relate to handling of exception values in BCIM mode.

Abstract: Various innovations facilitate the use of intra-picture prediction modes such as palette prediction mode, intra block copy mode, intra line copy mode and intra string copy mode by an encoder or decoder when wavefront parallel processing (“WPP”) is enabled. For example, for a palette coding/decoding mode, an encoder or decoder predicts a palette for an initial unit in a current WPP row of a picture using previous palette data from a previous unit in a previous WPP row of the picture. Or, as another example, for an intra copy mode (e.g., intra block copy mode, intra string copy mode, intra line copy mode), an encoder enforces one or more constraints attributable to the WPP, or a decoder receives and decodes encoded data that satisfies one or more constraints attributable to WPP.