Towards high dynamic range extensions of HEVC: subjective evaluation of potential coding technologies

Abstract

This paper reports the details and results of the subjective evaluations conducted at EPFL to evaluate the responses to the Call for Evidence (CfE) for High Dynamic Range (HDR) and Wide Color Gamut (WCG) Video Coding issued by Moving Picture Experts Group (MPEG). The CfE on HDR/WCG Video Coding aims to explore whether the coding efficiency and/or the functionality of the current version of HEVC standard can be significantly improved for HDR and WCG content. In total, nine submissions, five for Category 1 and four for Category 3a, were compared to the HEVC Main 10 Profile based Anchor. More particularly, five HDR video contents, compressed at four bit rates by each proponent responding to the CfE, were used in the subjective evaluations. Further, the side-by-side presentation methodology was used for the subjective experiment to discriminate small differences between the Anchor and proponents. Subjective results shows that the proposals provide evidence that the coding efficiency can be improved in a statistically noticeable way over MPEG CfE Anchors in terms of perceived quality within the investigated content. The paper further benchmarks the selected objective metrics based on their correlations with the subjective ratings. It is shown that PSNR-DE1000, HDR-VDP-2, and PSNR-Lx can reliably detect visible differences between the proposed encoding solutions and current HEVC standard.

Benchmarking of objective quality metrics for HDR image quality assessment

“…Narwaria et al [15] found that HDR-VQM was performing significantly better than HDR-VDP-2 for both video and still image content. However, our results show that both metrics have similar performance, while it was reported in [9] that HDR-VQM performs lower than HDR-VDP-2 for HDR video compression. The divergence between these findings might be due to the contents and types of artifacts considered in the different studies.…”

“…Finally, Narwaria et al [15] have reported that their HDR-VQM metric performs similar or slightly better than HDR-VDP-2 for HDR image quality assessment. Regarding HDR video quality assessment, four studies were also reported by Azimi et al [27], Rerabek et al [28], Hanhart et al [9], and Narwaria et al [15]. The authors of [15] found that HDR-VQM is the best metric, far beyond HDR-VDP-2, in contradiction to the findings of [9], which showed lower performance for HDR-VQM when compared to HDR-VDP-2.…”

“…Regarding HDR video quality assessment, four studies were also reported by Azimi et al [27], Rerabek et al [28], Hanhart et al [9], and Narwaria et al [15]. The authors of [15] found that HDR-VQM is the best metric, far beyond HDR-VDP-2, in contradiction to the findings of [9], which showed lower performance for HDR-VQM when compared to HDR-VDP-2. Also, the other two studies found that HDR-VDP-2 has the highest correlation.…”

“…However, instead of using the exact mathematical log operation, profile C uses a piecewise linear approximation, defined by re-interpreting the bit-pattern of the half-logarithmic IEEE representation of floatingpoint numbers as integers, which is exactly invertible [8]. MPEG is also starting a new standardization effort on HDR video [9], revealing the growing importance of HDR technologies.…”

Objective and subjective evaluation of High Dynamic Range video compression

“…Recently, Hanhart et al [17] conducted an evaluation of nine HDR video compression algorithms submitted in response to the Motion Pictures Experts Group (MPEG) committee's Call for Evidence (CfE) [25] to evaluate the feasibility of supporting HDR and Wide Color Gamut (WCG) content using the High Efficiency Video Codec (HEVC) [43] encoder. The paper concludes that the proposals submitted to MPEG can noticeably improve the standard HDR video coding technology and QA metrics such as PSNR-DE1000, HDR-VDP2 and PSNR-Lx can reliably detect visible difference.…”