Abstract: Systems and techniques are provided for processing video data. For example, the systems and techniques can include obtaining a current picture of video data and obtaining reference pictures for the current picture from the video data. A merge mode candidate can be determined for the current picture. First and second motion vectors can be identified for the merge mode candidate. A motion vector search strategy can be selected for the merge mode candidate from a plurality of motion vector search strategies. The selected motion vector search strategy can be associated with one or more constraints corresponding to at least one of the first motion vector or the second motion vector. The selected motion vector search strategy can be used to determine refined motion vectors based on the first motion vector, the second motion vector, and the reference pictures. The merge mode candidate can be processed using the refined motion vectors.

Abstract: An example device includes memory configured to store the video data and one or more processors implemented in circuitry and communicatively coupled to the memory. The one or more processors are configured to determine at least one of a temporal candidate or a history-based candidate and determine at least one non-adjacent candidate, wherein the at least one non-adjacent candidate is from a unit that is not adjacent to a current prediction unit (PU). The one or more processors are configured to determine an advanced motion vector predictor (AMVP) candidate list including the at least one of the temporal candidate or the history-based candidate and the at least one non-adjacent candidate. The at least one non-adjacent candidate is added to the AMVP candidate list after the temporal candidate or before the history-based candidate. The one or more processors are configured to code the current PU based on the AMVP candidate list.

Abstract: An example device includes one or more processors configured determine a plurality of subblocks for a current block of video data. For each subblock, the one or more processors (a) generate initial motion vectors for a first prediction direction and a second prediction direction according to an affine motion model, and (b) determine, based on the initial motion vectors, a subblock bilateral matching cost for each respective offset among a plurality of offsets. For each respective offset, the one or more processors determine a respective summation of subblock bilateral matching costs. The one or more processors determine a lowest summation of subblock bilateral matching costs. The one or more processors select an offset associated with the lowest summation of subblock bilateral matching costs. The one or more processors modify the affine motion model based on the selected offset and code the current block based on the modified affine motion model.

Abstract: A device for decoding video data comprises one or more processors configured to: obtain a syntax element from a bitstream that includes an encoded representation of the video data; determine, based on the syntax element, that a template-matching tool is enabled; based on the template-matching tool being enabled, applying the template-matching tool to generate a prediction block for a current coding unit (CU) of the video data; and reconstruct the current CU based on the prediction block for the current CU.

Abstract: A method of decoding video data includes generating a fusion of predictors from two or more reference lines of samples relative to a block of video data based on an intra-prediction mode. The method further includes decoding the block of video data using the fusion of predictors and the intra-prediction mode.

Abstract: A device for decoding video data may be configured to apply a deblocking filter to a block of video data to determine a first filtered block; apply a second filter to the block of video data in parallel with the deblocking filter to determine a second filtered block, wherein the second filter comprises one of a guided filter, a bilateral filter, or an adaptive loop filter; combine the first filtered block and the second filtered block to determine a combined block; apply a third filter to the combined block to determine a third filtered block; process the third filtered block to determine a decoded version of the block of video data; and output the decoded version of the block of video data.

Abstract: Systems and techniques are described for processing video data. For example, an apparatus can obtain a block of video data encoded using inter-prediction. In some examples, the apparatus can determine a direction associated with the block of video data, for instance based on pixels of the block of video data, based on pixels of at least one neighboring block of the block of video data, or based on information associated with a geometric partitioning mode (GPM) associated with the block of video data. The apparatus can apply a non-separable transform to the block of video data, for instance to decode or encode the video data. In some examples, the apparatus can apply the non-separable transform to the block according to the direction associated with the block of video data.

Abstract: A method of coding video data comprises determining, based on a comparison of a threshold and a quantity of reference samples in a selected template, whether the selected template is allowed, wherein a mode index indicates which template from among a plurality of templates is the selected template, wherein each of the templates includes a different set of reconstructed samples that neighbor a current coding unit (CU) of a current picture of the video data; based on determining that the selected template is allowed and that a convolutional cross-component model (CCCM) mode is to be used, applying the CCCM mode to predict chroma samples of the current CU based on reconstructed luma samples of the current CU and the reference samples in the selected template; and; and encoding or decoding the current CU based on the predicted chroma samples of the current CU.

Abstract: A video decoder can be configured to determine a number of allowed non-zero coefficients for a block of video data based on a size of the block; obtain a set of dequantized coefficients for the block, wherein the set of dequantized coefficients comprises a first subset of dequantized coefficients that includes non-zero dequantized coefficients and a second subset of dequantized coefficients that includes all zero coefficients, wherein a number of coefficients in the first subset of dequantized coefficients is equal to the number of allowed non-zero coefficients for the block of video data; apply an inverse low-frequency non-separable transform (LFNST) to the first subset of dequantized coefficients to determine a first intermediate subset of coefficients; and apply an inverse separable transform to the first intermediate subset of coefficients and at least a portion of the second subset of coefficients to determine a block of reconstructed residual values.

Abstract: An example device for decoding video data includes one or more processors implemented in circuitry and configured to: decode a coding tree unit (CTU) of video data, the CTU including a luminance (luma) block and a chrominance (chroma) block, to produce a decoded luma block and a decoded chroma block; determine that a chroma sample of the decoded chroma block is on a first side of an adaptive loop filter (ALF) virtual boundary and that a co-located luma sample of the decoded luma block is on a second side of the ALF virtual boundary, the co-located luma sample being co-located with the chroma sample, the first side being different than the second side; and in response to determining that the chroma sample is on the first side and the luma sample is on the second side, disable cross-component adaptive loop filtering (CC-ALF) for the chroma sample.

Abstract: A video decoder determines, based on a block size of a current block and a low-frequency non-separable transform (LFNST) syntax element, a zero-out pattern of normatively defined zero-coefficients. The LFNST syntax element is signaled at a transform unit (TU) level. Additionally, the video decoder determines transform coefficients of the current block. The transform coefficients of the current block include transform coefficients in an LFNST region of the current block and transform coefficients outside the LFNST region of the current block. As part of determining the transform coefficients of the current block, the video decoder applies an inverse LFNST to determine values of one or more transform coefficients in the LFNST region of the current block. The video decoder also determines that transform coefficients of the current block in a region of the current block defined by the zero-out pattern are equal to 0.

Abstract: A video encoder maintains a first reference picture list; maintains a second reference picture list; determines that a picture is an instantaneous decoding refresh (IDR) picture; determines that reference picture list syntax elements are present in a slice header for the IDR picture; and in response to determining that the picture is the IDR picture and that the reference picture list syntax elements are present in the slice header for the IDR picture, updates the first reference picture list and the second reference picture list such that no picture in the first reference picture list and no picture in the second reference picture list precedes, in output order or decoding order, any preceding instant random access point (IRAP) picture in decoding order.

Abstract: A video coder may be configured to code video data by performing splitting of a coding unit (CU) of video data using intra sub-partition (ISP) to form a set of prediction blocks. The video coder may group a plurality of the prediction blocks from the set of prediction blocks into a first prediction block group (PBG). The video coder may reconstruct samples of prediction blocks included in the first PBG independently of samples of other prediction blocks included in the first PBG.

Abstract: An example device for decoding video data includes one or more processors configured to determine merge mode information for a current block, the merge mode information indicating that motion information for a current block is to be predicted using a first predictor motion vector and a second predictor motion vector; determine a first motion vector difference (MVD) for the first predictor motion vector and a second MVD for the second predictor motion vector, the second MVD being different than the first MVD; form a first motion vector equaling a combination of the first motion vector predictor and the first MVD; form a second motion vector equaling a combination of the second motion vector predictor and the second MVD; generate a prediction block using the first motion vector and the second motion vector; and decode the current block using the prediction block.

Abstract: A video decoder may be configured to determine a motion vector and a motion vector precision for a current block; identify a current block template within the current picture; search within a search area for a final reference block template that corresponds to the current block template, wherein to search within the search area, the one or more processors are further configured to: identify an initial reference block template based on the motion vector, search other reference block templates around the initial reference block template using a step size that is set to an initial step size, and iteratively reduce the step size from the initial step size until the step size is set to a final step size that equals the motion vector precision; determine a prediction block for the current block based on the final reference block template.

Abstract: Example techniques and devices are disclosed for coding video data. An example device includes memory configured to store the video data and one or more processors implemented in circuitry and communicatively coupled to the memory. The one or more processors are configured to determine that multiple-hypothesis prediction (MHP) is enabled. The one or more processors are configured to, based on determining that MHP is enabled, determine a maximum number of merge candidates for a MHP merge candidate list. The one or more processors are configured to, based on the maximum number of merge candidates for the MHP merge candidate list, determine the MHP merge candidate list. The one or more processors are configured to code the video data based on the MHP merge candidate list.

Abstract: A method of encoding or decoding video data includes constructing a list of chroma intra-prediction modes for a chroma block of a current block of the video data, wherein constructing includes adding intra-prediction modes of a first group to the list of chroma intra-prediction modes, the first group comprising two or more intra-prediction modes derived from intra-prediction modes of two or more co-located luma blocks of the current block that are co-located with the chroma block; determining an intra-prediction mode for the chroma block from the list of chroma intra-prediction modes; and encoding or decoding the chroma block based on the intra-prediction mode.

Abstract: An example device for decoding video data includes a memory configured to store video data; and one or more processors implemented in circuitry and configured to: decode a current block of the video data to form a decoded block; determine that a current sample of the decoded block neighbors a sample along a virtual boundary in the decoded block and neighbors one or more samples that are not along any virtual boundary in the decoded block; compute band information for cross component sample adaptive offset (CCSAO) for the current sample using at least one of the one or more samples that are not along any virtual boundary in the decoded block and without using the sample along the virtual boundary; and perform CCSAO on the current sample using the band information.

Abstract: A video coder may adaptively determine whether to apply an inter-MTS (multiple transform set) mode to video data. The video coder may adaptively determine one or more of a maximum block size or a minimum block size for applying an inter-MTS mode. The video decoder may determine whether the inter-MTS mode is enabled for a block of video data based on a size of the block compared to one or more of the minimum block size or the maximum block size. and code the block using the inter-MTS mode based on the inter-MTS mode being enabled. Coding the block using the inter-MTS mode includes applying one or more transforms of a plurality of transforms to transform coefficients associated with the block of video data.

Abstract: A method of encoding or decoding video data includes determining that a block vector difference (BVD) value is non-zero, wherein the BVD value is indicative of a difference between a block vector for a current block of the video data and a block vector predictor, and wherein the block vector points to a reference block based on samples in a same picture as the current block; and encoding or decoding a value for the BVD value, without signaling or parsing syntax information indicating whether an absolute value of the BVD value is greater than one.