Apple Inc.

Other

Linfeng Guo

Xiaohua Yang

Francesco Iacopino

Xiang Fu

Hao Pan

Haitao Guo

Krishnakanth Rapaka

Munehiro Nakazato

Felix Chou

Alexandros Michael Tourapis

Guichun Li

Jim Chen Chou

Arash Vosoughi

Wei Li

Alican Nalci

Ke Chen

Hilmi Enes Egilmez

Ying Jian He

Haiyan He

Ye Cong

Xu Zhao

Dzung T Hoang

Van Luong Pham

Krishna Rapaka

Mukta Gore

Low complexity, hardware-friendly techniques are proposed for video coding systems to mitigate banding artifacts while maintaining the compression efficiency. In general, the proposed techniques consist of two stages including a banding detection stage and a de-banding stage. The banding detection stage may identify the image/video regions where the banding artifact may be present based on gradient information and other information. The de-banding stage may apply corrective techniques to regions identified as likely to possess banding artifacts. In one embodiment, the de-banding adapts the filtering logic proposed by prior video coding standards for other filtering applications to mitigate banding. When implemented over the AV1 video coding standard and the AOM Video Model (AVM) reference software, the proposed technique improves subjective quality significantly at a reasonable hardware implementation cost. The methods and embodiments presented in this document can be beneficial find application in a wide variety of image/video coding standards and systems.

Techniques for contouring/banding artifact removal in compressed image/video

In one implementation, a method of generating a bit stream encoding a video stream is performed by a device including one or more processors and non-transitory memory. The method includes decomposing a video stream into a plurality of frequency band video streams. The method includes determining a target bitrate and determining, for each frequency band video stream, a respective frequency band bit rate based on the target bit rate. The method includes encoding each of the plurality of frequency band video streams at its respective frequency band bit rate and transmitting, over a channel, each encoded frequency band video stream.

Multi-band rate control

Techniques for encoding video with reduced frame-boundary artifacts are presented. The techniques include a video encoding method, where, when skip mode is selected as a motion prediction coding mode for a pixel block predicted from a reference block of a reference frame, estimating an amount of the reference block that extends beyond the edge of the reference frame. If the amount beyond the edge does not exceed a threshold, the prediction may be coded with skip mode. If the amount beyond the edge exceeds a threshold, the pixel block may be partitioned, and the partitioned blocks may be coded with motion prediction.

Frame boundary artifacts removal

Techniques are disclosed for coding image data adaptively at different levels of downscaling. Such techniques may involve partitioning input data into pixel blocks for coding and performing content analysis on the pixel blocks. The pixel blocks may be input to block coders that operate at different pixel block sizes, which may code the pixel blocks input to them at their respective sizes. Except when a block coder operates at the partitioning size, block coders that operate at different pixel block sizes may perform downscaling of the pixel blocks to match their size with the block coders' respective coding size. A block decoder may invert the coding operations performed by the block coders, decoding coded image data at respective pixel block sizes, then upscaling decoded image data obtained therefrom to a common pixel block size. Image reconstruction may synthesize a resultant image from the decode pixel block data output by the decoders. Quality enhancements may be added by neural network processing systems that have been trained to other segmented images.

Deep quality enhancement of adaptive downscaled coding for image compression

Techniques are disclosed for developing quantization matrices for use in video coding. According to these techniques a first quantization matrix may be derived from a second quantization matrix by scaling quantization values of the second quantization matrix by scaling parameters. The scaling parameters may increase according to distance between each matrix position and a matrix origin, they may be derived from characteristics of a video sequence to be coded, or both. The first quantization matrix may be communicated to a decoder. Thereafter, a video sequence may be coded predictively. As part of the coding, pixel data of the video sequence may be transformed to a plurality of frequency domain coefficients, and the frequency domain coefficients may be quantized according to the first quantization matrix.

Techniques for calculation of quantization matrices in video coding

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Cupertino, CA, United States of America

Linfeng Guo