The Alliance for Open Media (AOMedia) has been exploring new coding tools to enhance AV1 capabilities. Semi-Decoupled Partitioning (SDP), originally designed for intra frames in research-v2.0.0, improves coding by decoupling luma and chroma block partitioning. This study extends SDP to inter frames by introducing intra region coding, where the root node is explicitly signaled in the bitstream. Within the intra region, luma components of the intra-coded blocks can be further split, while chroma components remain unsplit. The experiments are implemented on the 8thanchor, research-v8.0.0, of AVM reference software with CTCv7, and experimental results show that the proposed method can achieve 0.12%, 2.39%, 2.58% coding gain for Y, U, and V component separately with random access configuration and 5% encoding time increase and almost no decoding time increase.

The latest initiative of Alliance for Open Media Video (AOM), named as AOM Video Model (AVM), is expected to introduce new coding tools to enhance compression benefits. Semi-Decoupled Partitioning (SDP) in AVM decouples the shared tree to support separate block partitioning for the luma and chroma channels from 64×64. Further, Chroma from Luma (CfL) is a chroma-only coding tool in AVM that applies collocated luma reconstructed samples in predicting chroma samples. The dependency of reconstructed luma samples in CfL can result in a delayed decoding process of chroma blocks in separate tree partitioning and introduce a worst-case latency of 4096 luma samples. In response, this study proposes a CfL constrained strategy to reduce the worst-case latency by selectively disallowing the CfL mode in a given chroma partition tree. Detailed latency analysis is also provided to confirm the reduction of worst-case latency to 2048 luma samples. The experiments are implemented on top research-v10.0.0 under Common Test Conditions (CTC) V7. The experimental results show that when the worst-case decoder latency is minimized to 2048 luma samples, the coding loss can be kept to minimal with an average loss of 0.02% for the YUV components in random access configurations with no change in encoder and decoder timings.

Intra Block Copy (IntraBC) is a key coding tool for screen content video, enabling blocks to reference previously reconstructed regions within the same frame. While IntraBC was introduced in AV1 and further enhanced in VVC, the AVM development framework offers new opportunities to improve its coding efficiency and hardware compatibility. This paper proposes three enhancements adopted into the AVM reference software: (1) a unified and extended local reference buffer design supporting multiple superblock sizes with fixed memory constraints; (2) a decoupled global-local search strategy that improves block vector prediction efficiency; and (3) the integration of intra Block-Adaptive Weighted Prediction (BAWP) into local IntraBC. Experimental results show significant screen content coding gains: -3.53%, -2.25%, -1.43% (YUV-PSNR) for all intra, random access and low delay, respectively, with minimal runtime overhead. These contributions have been adopted into the AVM standard and reference software.

360-degree video streaming for VR visualisation is characterised by large transmission data volume and stringent interactive latency demands; hence guaranteeing suitable transmission quality, while meeting the existing constraints, is highly challenging. This paper addresses the relevant grand challenge presented at MMSys 2024 on 360-degree video on-demand streaming, aiming at designing and implementing a 360-degree video on-demand streaming solution using the open-source evaluation platform E3PO. The proposed solution incorporates several strategies including viewport prediction, tiling, encoding tile selection for streaming and upsampling. The source code for the proposed solution will be publicly available on Github1.

Video Quality Assessment (VQA) is an integral part of any video coding processes. The Versatile Video Coding (VVC) applies Peak Signal-To-Noise (PSNR) spherical objective quality metrics in the VQA of 360° videos. However, these metrics fail to display compatibility to be integrated with the rectilinear functionalities of VVC. In response, this paper proposes Weighted Craster Parabolic Projection Peak Signal-to Noise Ratio (WCPPPSNR), a novel spherical objective quality metric for 360° video that improves the existing CPPPSNR by providing rectilinear functionalities to support VVC. The subjective experiments conducted, validate the proposed metric to be a good candidate for VQA of 360° video while the use case test reports that the integration of the proposed metric with VVC can improve the coding efficiency up to 2.43% with reference to the anchor implementation of VVC Test Model (VTM) 2.2.

Widespread adoption of communication tools, including screen sharing and video conferencing, is creating an increasing need for better compression of artificially generated (screen) content. This type of content is typically characterised by distinct features, including sharp edges and repeating patterns, and as such it benefits from ad-hoc coding tools designed specifically to exploit such features. Among these tools, the emerging Versatile Video Coding (VVC) standard includes Intra Block Copy (IBC), a successful technique whereby reconstructed portions of the current frame are copied as predictions for a given block of samples. However, IBC can only represent translational motion and as such, it cannot predict geometrical transformations common in screen contents. In this paper, a novel tool to improve the efficiency of VVC screen content coding is proposed extending the functionality of IBC. The tool exploits the fact that screen content contains predictable transformations of contents including zooms, rotations and stretches, which may be useful to improve IBC predictions. By appropriately defining affine transformations that are applied on the IBC reference samples, and compacting the information necessary to represent these transformations, higher compression efficiency can be achieved at limited impact in complexity. Extensive experiments showed that the proposed solution outperforms state-of-the-art schemes, achieving consistent coding gains, up to 5.4% for specific screen content sequences.