Zoom Communications, Inc.

Minxia Yang

Jing Wu

Rui Li

Yi Guo

Zhichu He

Bo Ling

Yichen Zhang

Shiyan Zhang

Methods, systems, and apparatus, including computer programs encoded on computer storage media for fast search of transform kernel selection. A set of transform kernels are selected. Multiple images are encoded via the AV1 coded using the selected transform kernels. The encoded images are transmitted to another computing device.

Fast search and selection of a transform kernel for AV1 encoding

In one example, a video encoder divides a superblock of a video frame into subblocks. The dividing includes dividing the superblock according to a first and second partitioning schemes to generate a first and second combination of subblocks, respectively. The number of non-zero residuals in each subblock in the first and second combinations of subblocks is less than a corresponding threshold set for a size of the subblock. The encoder determines the subblocks for the superblock as the first combination of subblocks based on a first cost value associated with the first combination of subblocks being lower than a second cost value associated with the second combination of subblocks. The encoder further encodes the superblock into a video bitstream representing the video by encoding the subblocks.

Reducing grid artifacts in video frames

Fast parameter search for chroma from luma (CFL) intra prediction in video encoding is provided. A video encoder determines a value of a parameter of a linear CFL predictor for a coding block of a frame of a video. The determining includes dividing a search range within a value range of the parameter into three portions by a starting value: the starting value and values on two sides of the starting value. The encoder determines cost values of parameter values from the three portions and select the value of the parameter that corresponds to the lowest cost value. The encoder further encodes the coding block of the frame into a bitstream representing the video using the CFL predictor with the selected value of the parameter.

Fast parameter search for chroma from luma intra prediction in video coding

Deriving in-loop filter parameters via training for video encoding is provided. A video encoder performs inter prediction for a frame in a set of frames of the video to generate prediction residuals for the frame. The inter prediction for the frame is performed based on a reconstructed frame in the set of frames filtered using an in-loop filter. The value of a parameter of the in-loop filter is determined by determining, for each candidate in-loop filter parameter value, a visual quality metric for a set of training frames in training video sequences filtered by the in-loop filter. The candidate in-loop filter parameter value that corresponds the highest visual quality metric can be selected as the value of the parameter of the in-loop filter. The video encoder further encodes the prediction residues of the frame and the parameter of the in-loop filter into a bitstream representing the video.

Deriving in-loop filter parameters for video coding

Constructing a motion vector candidate list for inter-prediction in video coding is provided. A video encoder performs inter prediction for a frame of the video to generate prediction residuals. The inter prediction is performed using motion vectors (MVs) for blocks of the frame. To determine the motion vector of a block, the encoder determines an integer-valued MV for the block based on a reference frame and selects, based on the integer-valued MV, a subset of candidate MVs from a list of MVs including MVs of neighboring blocks. The encoder identifies a MV from the subset of candidate MVs for the block and searches in a neighborhood of the identified MV for a refined MV. The encoder calculates the prediction residuals for the block based on a reference block in the reference frame pointed by the refined MV and encodes the prediction residuals into a bitstream representing the video.

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Hangzhou, China

Minxia Yang