公开(公告)号：US20240040124A1

公开(公告)日：2024-02-01

申请号：US18358094

申请日：2023-07-25

Applicant: Apple Inc.

Inventor： Alican NALCI ,  Yunfei ZHENG ,  Hilmi Enes EGILMEZ ,  Yeqing WU ,  Yixin DU ,  Alexandros TOURAPIS ,  Jun XIN ,  Hsi-Jung WU ,  Arash VOSOUGHI ,  Dzung T. HOANG

IPC: H04N19/13 ,  H04N19/70 ,  H04N19/61 ,  H04N19/176

CPC classification number: H04N19/13 ,  H04N19/70 ,  H04N19/61 ,  H04N19/176

Abstract: A flexible coefficient coding (FCC) approach is presented. In the first aspect, spatial sub-regions are defined over a transform unit (TU) or a prediction unit (PU). These sub-regions organize the coefficient samples residing inside a TU or a PU into variable coefficient groups (VCGs). Each VCG corresponds to a sub-region inside a larger TU or PU. The shape of VCGs or the boundaries between different VCGs may be irregular, determined based on the relative distance of coefficient samples with respect to each other. Alternatively, the VCG regions may be defined according to scan ordering within a TU. Each VCG can encode a 1) different number of symbols for a given syntax element, or a 2) different number of syntax elements within the same TU or PU. Whether to code more symbols or more syntax elements may depend on the type of arithmetic coding engine used in a particular coding specification. For multi-symbol arithmetic coding (MS-AC), a VCG may encode a different number of symbols for a syntax element. For example, to encode absolute coefficient values inside a TU after performing a transform such as the discrete cosine transform (DCT), a VCG region may be defined around lower-frequency transform coefficients and for that VCG M-symbols can be encoded the absolute coefficient values. Another VCG region can be defined around the higher-frequency transform coefficients to encode K-symbols, where K may be different than M. For binary arithmetic coders (BACs), FCC allows for coding a variable number of syntax elements in different VCGs. In this case, one VCG in a TU may code M-syntax elements associated with signaling the absolute coefficient value, where each one of the M-syntax elements may have 2-symbols. Probability models and context derivation rules may be tailored for each VCG in a given TU or PU. Since each VCG may code a different number of symbols or syntax elements in different spatial locations of a TU or PU, different context models may be used for each VCG to provide better granularity for entropy modeling for arithmetic coding. Furthermore, different VCGs may also use different entropy coders including combinations of arithmetic coding, Golomb-Rice coding, Huffman coding.

公开(公告)号：US20250080759A1

公开(公告)日：2025-03-06

申请号：US18794601

申请日：2024-08-05

Applicant: APPLE INC.

Inventor： Guoxin JIN ,  Yeqing WU ,  Yunfei ZHENG ,  Dazhong ZHANG ,  Dzung T. HOANG ,  Felix C. FERNANDES ,  Van Luong PHAM ,  Jiancong LUO ,  Yixin DU ,  Hilmi Enes EGILMEZ ,  Alican NALCI ,  Jun XIN ,  Hsi-Jung WU

IPC: H04N19/176 ,  H04N19/117 ,  H04N19/159 ,  H04N19/46 ,  H04N19/70 ,  H04N19/82

Abstract: Techniques are disclosed for coding video in applications where regions of video are inactive on a frame to frame basis. According to the techniques, coding processes update and reconstruct only a subset of pixel blocks of pixels within a frame, while other pixel blocks are retained from a previously coded frame stored in a coder's or decoder's reference frame buffer. The technique is called Backward Reference Updating (or “BRU”) for convenience. At a desired pixel block granularity, based on the activity between a current frame to be coded and its reference frame(s), BRU will only perform prediction, transform, quantization, and reconstruction on selected regions that are determined to be active. The reconstructed pixels in these active regions are directly placed onto a specified reference frame in memory instead of creating a new frame. Therefore, fewer memory transfers need to be performed.

公开(公告)号：US20250142059A1

公开(公告)日：2025-05-01

申请号：US18610737

申请日：2024-03-20

Applicant: Apple Inc.

Inventor： Van Luong PHAM ,  Arash VOSOUGHI ,  Dzung T. HOANG ,  Linfeng GUO ,  Alican NALCI ,  Guichun LI ,  Hilmi Enes EGILMEZ ,  Alexandros TOURAPIS

IPC: H04N19/117 ,  H04N19/14 ,  H04N19/176 ,  H04N19/196 ,  H04N19/82

Abstract: 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.