Justin Ridge

High Performance, Low Complexity Video Coding and the Emerging HEVC Standard

This paper describes a low complexity video codec with high coding efficiency. It was proposed to the high efficiency video coding (HEVC) standardization effort of moving picture experts group and video coding experts group, and has been partially adopted into the initial HEVC test model under consideration design. The proposal utilizes a quadtree-based coding structure with support for macroblocks of size 64 × 64, 32 × 32, and 16 × 16 pixels. Entropy coding is performed using a low complexity variable length coding scheme with improved context adaptation compared to the context adaptive variable length coding design in H.264/AVC. The proposals interpolation and deblocking filter designs improve coding efficiency, yet have low complexity. Finally, intra-picture coding methods have been improved to provide better subjective quality than H.264/AVC. The subjective quality of the proposed codec has been evaluated extensively within the HEVC project, with results indicating that similar visual quality to H.264/AVC High Profile anchors is achieved, measured by mean opinion score, using significantly fewer bits. Coding efficiency improvements are achieved with lower complexity than the H.264/AVC Baseline Profile, particularly suiting the proposal for high resolution, high quality applications in resource-constrained environments.

Low complexity video coding and the emerging HEVC standard

This paper describes a low complexity video codec with high coding efficiency. It was proposed to the High Efficiency Video Coding (HEVC) standardization effort of MPEG and VCEG, and has been partially adopted into the initial HEVC Test Model under Consideration design. The proposal utilizes a quad-tree structure with a support of large macroblocks of size 64×64 and 32×32, in addition to macroblocks of size 16×16. The entropy coding is done using a low complexity variable length coding based scheme with improved context adaptation over the H.264/AVC design. In addition, the proposal includes improved interpolation and deblocking filters, giving better coding efficiency while having low complexity. Finally, an improved intra coding method is presented. The subjective quality of the proposal is evaluated extensively and the results show that the proposed method achieves similar visual quality as H.264/AVC High Profile anchors with around 50% and 35% bit rate reduction for low delay and random-access experiments respectively at high definition sequences. This is achieved with less complexity than H.264/AVC Baseline Profile, making the proposal especially suitable for resource constrained environments.

Efficient transform-domain size and resolution reduction of images

This paper describes techniques for adapting a transform-based image (such as JPEG) so that it conforms to specific compressed size or dimension criteria. For compressed size adaptation, the proposed method operates efficiently in the transform domain, but yields visually improved results when compared to existing approaches. For resolution adaptation, the proposed method results in a speed improvement of 76% over the baseline algorithm and 31% over other previous work, with minimal or no difference in overall visual quality.

FGS Coding with Adaptive Reference for Low-Delay Applications

This paper presents the design of a fine granularity SNR scalable video coder for low-delay applications. Specifically, temporal prediction is introduced into the FGS layer of closed-loop P-frames. The prediction is formed adaptively from the enhancement layer reference and the base layer reference, utilizing information coded in the base layer. This novel FGS coder can control drift that may occur due to partial decoding of the FGS layer, while at the same time achieving high coding efficiency. Effort is also spent on reducing the complexity of the new solution by using low-complexity motion compensation and by minimizing additional transform operations. With minimal increase in the complexity, the FGS coding performance of closed-loop P-frames can be improved by as much as 4.5 dB for one FGS layer on a base layer coded at QP 42.

Fine-grained scalability for H.264/AVC

An algorithm for fine-grained scalability (FGS) in H.264/AVC is presented. This algorithm is included in Working Draft 2 of the H.264/AVC scalable extension. Encoding block coefficients in a cyclical manner places “higher-value” bits earlier in the bit stream. If the bit stream is truncated, higher-value bits are therefore more likely to be retained. By arranging the bit stream in such a manner, a PSNR gain of up to 0.5 dB can be achieved versus non-cyclical coding, depending upon the sequence and bit stream truncation point.

Improved video coding with residual prediction for extended spatial scalability

Annex G has been added to the H.264/AVC video coding standard to improve the scalability of coded video. In this annex, residual prediction is one of the main coding tools that provide efficient inter-layer prediction with moderate coding complexity. However, when residual prediction is used in an extended spatial scalability scenario, it is reported that certain visual artifacts can appear, which results in a perceived quality degradation. This paper provides a detailed analysis of the problem. Based on the analysis, a solution that involves a modified mode decision process is suggested. With the proposed method, the reported visual artifact may be completely prevented. Meanwhile, the proposed solution does not require any change to decoder and therefore does not incur any overhead to decoder complexity.