Kenneth Andersson

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.

HEVC Deblocking Filter

This paper describes the in-loop deblocking filter used in the upcoming High Efficiency Video Coding (HEVC) standard to reduce visible artifacts at block boundaries. The deblocking filter performs detection of the artifacts at the coded block boundaries and attenuates them by applying a selected filter. Compared to the H.264/AVC deblocking filter, the HEVC deblocking filter has lower computational complexity and better parallel processing capabilities while still achieving significant reduction of the visual artifacts.

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.

Two HEVC encoder methods for block artifact reduction

The HEVC deblocking filter significantly improves the subjective quality of coded video sequences at lower bitrates. During the final phase of HEVC standardization, it was shown that the reference software encoder may produce visible block artifacts on some sequences with content that shows chaotic motion, such as water or fire. The paper analyses the reasons for blocking artifacts in such sequences and describes two simple encoder-side methods that improve the subjective quality on these sequences without degrading the quality on other content and without significant bitrate increase. The effect on subjective quality has been evaluated by a formal subjective test.

Towards a Test Automation Improvement Model (TAIM)

In agile software development, industries are becoming more dependent on automated test suites. Thus, the test code quality is an important factor for the overall system quality and maintainability. We propose a Test Automation Improvement Model (TAIM) defining ten key areas and one general area. Each area should be based on measurements, to fill the gap of existing assessments models. The main contribution of this paper is to provide the outline of TAIM and present our intermediate results and some initial metrics to support our model. Our initial target has been the key area targeting implementation and structure of test code. We have used common static measurements to compare the test code and the source code of a unit test automation suite being part of a large complex telecom subsystem. Our intermediate results show that it is possible to outline such an improvement model and our metrics approach seems promising. However, to get a generic useful model to aid test automation evolution and provide for comparable measurements, many problems still remain to be solved. TAIM can as such be viewed as a framework to guide the research on metrics for test automation artifacts.

HEVC deblocking filtering and decisions

The emerging High Efficiency Video Coding (HEVC) standard uses a block-based coding scheme, which may cause blocking artifacts, especially at lower bitrates. An adaptive in-loop deblocking filter is used in the standard to reduce visible artifacts at block boundaries. The deblocking filter detects artifacts at the block boundaries and attenuates them by applying a selected filter. This paper will present deblocking decisions and filtering operations that are used in HEVC.

Comparing Test and Production Code Quality in a Large Commercial Multicore System

A fundamental goal of software engineering practice is to ensure that code quality is maintained throughout its lifetime. Measuring and maintaining the quality of test code should be as important as measuring production (in-the-field) code. However, test code often seems to be a second class citizen compared to production code in terms of its upkeep and general maintenance. Many of the code features we might expect in test code are either absent or, included when they should not be. In this paper, we investigate four releases of an industrial embedded multi-core system from four perspectives and compare results for test code with corresponding production code. The four perspectives we considered as indicators of code quality. Firstly, we looked at whether test and production code conformed to a set of in-house designated design rules. Secondly, we explored whether test code contained a reasonable proportion of comment to code lines ratio relative to production code. Thirdly, we examined test and production code and the number of assertions in that code. Finally we investigated the relationship between faults and code features. In terms of results, test code did not fare well when compared with production code. An interesting and startling result related to the use of assertions, they were used liberally in test and production code. However, their effect, if triggered, was much larger in production code.

Guided just-in-time transcoding for cloud-based video platforms

Consumption of streamed video on-demand (VoD) content is driving rapid growth of fixed and mobile network traffic. VoD services are commonly run on cloud-based video platforms, where all processing is software-based. The VoD content is typically delivered using adaptive bit rate (ABR) streaming techniques. As the amount of content in an asset library grows, the required storage space and the associated cost increase. This is emphasized if several ABR representations per content are stored. To save storage space, lower quality ABR representations may be eliminated and re-generated based on the corresponding high quality representation as the content is requested, which is referred to as just-in-time (JIT) transcoding. In this paper, we investigate a scheme that can significantly reduce the computational complexity associated with JIT transcoding, called guided JIT transcoding. We analyze its performance when multiple HEVC-coded ABR representations with different spatial resolutions are utilized, showing that for a configuration with seven video representations with resolutions ranging from 1080p to 360p, storage requirements can be reduced by about 24% while software-based transcoding from 1080p to 720p can be performed at 46 fps on average using a single execution thread.

Corrections to “HEVC Deblocking Filter”

This is a correction to the “HEVC deblocking filter” article published in IEEE Transactions on Circuits and Systems for Video Technology, vol. 22, no. 12, Dec. 2012.

Low-complex adaptive post filter for enhancement of coded video

In this paper an adaptive filter that removes de-blocking and de-ringing artifacts and also enhances the sharpness of decoded video, which may be caused by zeroing high-frequency DCT coefficients, is presented. The solution is designed with consideration of mobile equipment with limited computational power and memory. Also, the solution is computationally scalable to be able to handle limited computational resources in different user cases. In the paper it is shown that the adaptive filter always keeps or increases the image quality, compared to the original decoded sequences, and that the amount of sharpening decreases with an decrease of bit-rate to limit amplification of coding artifacts or noise.