Abstract: Example techniques are described to illustrate multiple transform applied for Intra prediction residual. It may be used in the context of advanced video codecs, such as extensions of HEVC or the next generation of video coding standards. A video encoder and a video decoder may select transform subsets that each identify one or more candidate transforms. The video encoder and the video decoder may determine transforms from the selected transform subsets.

Abstract: A device may perform a first prediction process for a first block of video data to produce a first residual. The device may apply a first transform process to the first residual to generate first transform coefficients for the first block of video data and encode the first transform coefficients. The device may perform a second prediction process for a second block of video data to produce a second residual. The device may determine that a second transform process, which includes the first transform process and at least one of a pre-adjustment operation or a post-adjustment operation, is to be applied to the second residual. The device may apply the first transform process and the pre- or post-adjustment operation to the second residual to generate second transform coefficients for the second block. The coding device may code the first and second transform coefficients.

Abstract: A method of decoding video data includes determining a plurality of hypotheses of a current block based on a plurality of motion vectors. Each of the plurality of motion vectors is associated with one of the plurality of hypotheses, and each of the plurality of hypotheses is based on a set of samples in a reference picture having a motion vector that identifies a top-left sample of the set of samples. The method includes determining one or more neighboring samples in the same picture as the current block, for each of the plurality of hypotheses, determining respective correlation values between at least one sample of a respective hypothesis and at least one sample of the one or more neighboring samples, determining the motion vector for the current block based on the determined respective correlation values, and reconstructing the current block based on the determined motion vector.

Abstract: Systems and techniques are described for processing video data. For example, an apparatus can determine, for a sample of a first block of video data, histogram of gradient (HoG) information based on at least one sample from a second block neighboring the first block. The apparatus can determine, based on the HoG information, an angle associated with a direction of a gradient for the sample and the at least one sample from the second block neighboring the first block. The apparatus can further compare the angle to one or more predefined values and determine an index associated with the angle based on the comparison of the angle to the one or more predefined values. The apparatus can then determine, based on the index, an intra-prediction mode for coding the first block of video data.

Abstract: A video encoder and video decoder may be configured to disable subpicture processing in situations where reference picture scaling is enabled. In another example, when reference picture scaling is enabled, a video encoder may determine a reference picture scaling ratio for the reference picture resampling process based on a width of a scaling window (PicOutputWidthL) of the current picture and a height of the scaling window (PicOutputHeightL) of the current picture. The values of PicOutputWidthL and PicOutputHeightL are constrained, respectively, relative to a width of a scaling window (refPicOutputWidthL) of the reference picture and a height of the scaling window (refPicOutputHeightL) of the reference picture.

Abstract: Techniques related to derivation of motion vectors of a first color component (e.g., chroma component) from motion vectors of a second color component (e.g., luma component) are described. A video coder (e.g., video encoder or video decoder), for a CU coded in affine mode with 4:4:4 color format, may determine a motion vector for each sub-block of the luma block, and determine a motion vector for each sub-block of the chroma block based only on the motion vector for each co-located (also called collocated) sub-block of the luma block. However, for another CU coded in affine mode but with a color format other than 4:4:4 (e.g., 4:2:2 or 4:2:0), the video coder may determine a motion vector for each sub-block of the chroma block based on an average of two or more motion vectors of sub-blocks of the luma block.

Abstract: An method of decoding video data includes deriving, for a current block of video data and using decoder side intra mode derivation (DIMD), a list of intra modes using reconstructed samples of neighboring blocks; constructing, for the current block, a most probable mode (MPM) list, wherein constructing the MPM list comprises inserting, into the MPM list, at least one intra mode from the derived list of intra modes; and predicting, using a candidate selected from the constructed MPM list, the current block.

Abstract: A video encoder and video decoder are configured to code video data using multiple reference line processing. The video encoder and video decoder may determine a number of reference lines to use for multiple reference line processing based on an intra prediction mode, and decode a block of video data using the multiple reference line processing based on the number of reference lines.

Abstract: Systems and techniques are provided for coding video data. In some examples, a process may include obtaining a first plurality of prediction candidates associated with video data. The process may further include determining a first group of prediction candidates at least in part by applying a first grouping method to the first plurality of prediction candidates. The process may include reordering the first group of prediction candidates and selecting a first merge candidate from the reordered first group of prediction candidates. The process may further include adding the first merge candidate to a candidate list.

Abstract: Systems and techniques are described for processing video data. For instance, a process can include obtaining video data. The process can further include determining a classification band for a first sample of the video data using at least chroma information from the first sample, collocated luma information and collocated chroma information. The process can also include filtering at least the first sample of the video data based on the classification band.

Abstract: A video decoder may be configured to construct motion vector candidates using possible sign values, respective magnitudes of motion vector difference components, and a motion vector predictor for a block of video data, wherein the possible sign values include a positive sign value and a negative sign value, sort the motion vector candidates based on a cost for each of the motion vector candidates to create a sorted list, determine a respective motion vector difference sign for each motion vector difference coordinate based on a motion vector sign predictor index and the sorted list, and decode the block of video data using the respective magnitudes of motion vector difference coordinates and the respective motion vector difference sign for each motion vector difference component.

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: determine a number of multiple transform selection (MTS) candidates for a current block of video data, the number being greater than zero and different than four, the MTS candidates being MTS candidates other than a DCT2 candidate; determine one of the MTS candidates of the number of MTS candidates for the current block; inverse transform a transform block for the current block using the determined one of the MTS candidates to produce a residual block; and decode the current block using the residual block.

Abstract: An example method of encoding or decoding video data includes determining a motion vector for a block of video data using a decoder side motion vector derivation process that includes performing an iterative search process, wherein performing the iterative search process includes: determining a minimum cost through a previous search iteration; updating an overall minimum cost through a current search iteration; and terminating the iterative search process early based on a comparison of the minimum cost through the previous search iteration and the overall minimum cost through the current search iteration; and encoding or decoding the block of video data using the motion vector.

Abstract: An example device for coding video data determines for a first block of the video data whether to use a sub-block merge mode. Based on the determination not to use the sub-block merge mode for the first block, the device determines whether to use a merge mode with blending for the first block. Based on the determination to use the merge mode with blending for the first block, the device codes the first block with the merge mode with blending.

Abstract: Techniques are described of using Position Dependent Intra Prediction Combination (PDPC). A video coder such as a video encoder or a video decoder utilizes PDPC in cases where a current block intra mode predicted using an angular intra prediction mode.

Abstract: A method of decoding video data may comprise determining merge candidates for a block of video data and determining if a merge candidate of the merge candidates includes an additional inter prediction signal. If a merge candidate includes an additional inter prediction signal, the method may include disabling at least one decoder side motion vector derivation technique for use on a base prediction signal of the block of video data.

Abstract: An example device for coding video data includes a memory configured to store video data; and one or more processing units implemented in circuitry and configured to: store motion information for a first coding tree unit (CTU) line of a picture in a first history motion vector predictor (MVP) buffer of the memory; reset a second history MVP buffer of the memory; and after resetting the second history MVP buffer, store motion information for a second CTU line of the picture in the second history MVP buffer, the second CTU line being different than the first CTU line. Separate threads of a video coding process executed by the one or more processors may process respective CTU lines, in some examples.

Abstract: A method of coding video data includes determining that chroma related syntax elements of the video data are present for luma mapping with chroma scaling (LMCS) for a coding unit (CU) of the video data, coding a syntax element of the video data when the chroma related syntax elements are present for LMCS for the CU, the syntax element is indicative of a value for determining a scaling parameter for chroma scaling in LMCS, and coding a chroma block of the CU based on the scaling parameter for chroma scaling.

Abstract: Methods and apparatuses for encoding and decoding an intra prediction mode of a prediction unit of a chrominance component based on an intra prediction mode of a prediction unit of a luminance component are provided. When an intra prediction mode of a prediction unit of a luminance component is the same as an intra prediction mode in an intra prediction mode candidate group of a prediction unit of a chrominance component, reconstructing the intra prediction mode candidate group of the prediction unit of the chrominance component by excluding or replacing an intra prediction mode of the prediction unit of the chrominance component which is same as an intra prediction mode of the prediction unit of the luminance component from the intra prediction mode candidate group, and encoding the intra prediction mode of the prediction unit of the chrominance component by using the reconstructed intra prediction mode candidate group.

Abstract: An example device applies a primary transform to a current block of video data to create primary transform coefficients. The device determines whether intra sub-partitioning is applied to the current block of video data. The device applies a primary transform to the current block. The device also determines whether a primary transform size for the current block of video data is at least a predetermined size. Based on intra sub-partitioning being applied and the primary transform size being at least the predetermined size, the device applies a secondary transform to primary transform coefficients and codes the current block of video data based on the secondary transform.