Topic
Video quality
About: Video quality is a research topic. Over the lifetime, 13143 publications have been published within this topic receiving 178307 citations.
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29 Jul 2009
TL;DR: Using numerical simulations as well as real-life data from a multitude of subjective experiments, this paper attempts to shed more light on the distribution and variability of subjective ratings, the effects of discrete rating scales, and the number of subjects needed.
Abstract: Subjective video quality experiments are classical statistical measurements, and as such the mathematical tools for their analysis are well understood. However, there remain certain practical aspects that are rarely discussed, yet are essential to the design of efficient experiments. Using numerical simulations as well as real-life data from a multitude of subjective experiments, this paper attempts to shed more light on the distribution and variability of subjective ratings, the effects of discrete rating scales, and the number of subjects needed.
76 citations
TL;DR: A novel scheduling framework dubbed delAy Stringent COded Transmission (ASCOT) that featured by frame-level data protection and allocation overmultiple wireless access networks that outperforms existing transmission schemes in improving the video PSNR, reducing the end-to-end delay, and increasing the goodput.
Abstract: Delivering high-quality mobile video with the limited radio resources is challenging due to the time-varying channel status and stringent Quality of Service (QoS) requirements Multi-homing support enables mobile terminals to establish multiple simultaneous associations for enhancing transmission performance In this paper, we study the multi-homed communication of delay-constrained High Definition (HD) video in heterogeneous wireless networks The low-delay encoded HD video streaming consists exclusively of Intra (I) and Predicted (P) frames In the capacity-limited wireless networks, it is highly possible the large-size I frames experience deadline violations and induce severe quality degradations To address the challenging problem, we propose a novel scheduling framework dubbed del A y S tringent CO ded T ransmission (ASCOT) that featured by frame-level data protection and allocation over multiple wireless access networks First, we perform online video distortion estimation to simulate multi-homed transmission impairments according to the feedback channel status and input video data Second, we control the frame protection level by adapting the Forward Error Correction (FEC) coding redundancy and video data allocation to achieve target quality The performance of the proposed ASCOT is evaluated through semi-physical emulations in Exata using real-time H264 video streaming Experimental results show that ASCOT outperforms existing transmission schemes in improving the video PSNR (Peak Signal-to-Noise Ratio), reducing the end-to-end delay, and increasing the goodput Or conversely, ASCOT achieves the same video quality with approximately $20$ percent bandwidth conservation
76 citations
TL;DR: An algorithm which employs multiple Lagrange multipliers to find the constrained bit allocation is developed, and the solution is optimal for both CBR and VBR transmission if the full constrained tree is searched.
Abstract: We consider optimal encoding of video sequences for ATM networks. Two cases are investigated. In one, the video units are coded independently (e.g., motion JPEG), while in the other, the coding quality of a later picture may depend on that of an earlier picture (e.g., H.26x and MPEGx). The aggregate distortion-rate relationship for the latter case exhibits a tree structure, and its solution commands a higher degree of complexity than the former. For independent coding, we develop an algorithm which employs multiple Lagrange multipliers to find the constrained bit allocation. This algorithm is optimal up to a convex-hull approximation of the distortion-rate relations in the case of CBR (constant bit-rate) transmission. It is suboptimal in the case of VBR (variable bit-rate) transmission by the use of a suboptimal transmission rate control mechanism for simplicity. For dependent coding, the Lagrange-multiplier approach becomes rather unwieldy, and a constrained tree search method is used. The solution is optimal for both CBR and VBR transmission if the full constrained tree is searched. Simulation results are presented which confirm the superiority in coding quality of the encoding algorithms. We also compare the coded video quality and other characteristics of VBR and CBR transmission.
76 citations
TL;DR: It is shown that the HEVC-encoded YUV420 4K-UHD video at the target bit rate of 18 Mb/s is perceptually good enough in the usage of legacy DTV broadcasting systems with single channel bandwidths of 6 MHz and higher perceptual quality in the 420 YUV color format than in the YUV444 color format at the same target bitrates.
Abstract: In this paper, we present the experimental results with analysis for subjective quality assessment on 4K-ultra-high definition (UHD) video encoded by high efficiency video coding (HEVC) to investigate its feasibility for 4K-UHD TV broadcasting services. The subjective quality assessment on the HEVC-encoded (impaired) 4K-UHD video is conducted for the three target bitrates of 18, 23, and 36 Mb/s, the two color formats of YUV420 and YUV444, and the two viewing distances of 0.75 times the height of a display screen (H) and 1.5 H. The subjective quality assessment experiments on 4K-UHD test sequences show that the HEVC-encoded (impaired) YUV420 4K-UHD video even at the target bit of 18 Mb/s yields perceptual similar visual quality: 1) with MOS of 4.7 and 4.8 in 0.75 H and 1.5 H viewing distances, respectively, compared to the original YUV420 4K-UHD test video; and 2) with MOS of 4.8 in 1.5 H viewing distance, compared to the original YUV444 4K-UHD test video. This implies that the HEVC-encoded YUV420 4K-UHD video at the target bit rate of 18 Mb/s is perceptually good enough in the usage of legacy DTV broadcasting systems with single channel bandwidths of 6 MHz. It is also shown that the HEVC-encoded 4K-UHD test sequences mostly yield higher perceptual quality in the 420 YUV color format than in the YUV444 color format at the same target bitrates.
75 citations
19 Oct 2009
TL;DR: An approach for extracting visual attention regions based on a combination of a bottom-up saliency model and semantic image analysis and a novel quality metric is proposed which can exploit the attributes of visual attention information adequately.
Abstract: Most existing quality metrics do not take the human attention analysis into account. Attention to particular objects or regions is an important attribute of human vision and perception system in measuring perceived image and video qualities. This paper presents an approach for extracting visual attention regions based on a combination of a bottom-up saliency model and semantic image analysis. The use of PSNR (Peak Signal-to-Noise Ratio) and SSIM (Structural SIMilarity) in extracted attention regions is analyzed for image/video quality assessment, and a novel quality metric is proposed which can exploit the attributes of visual attention information adequately. The experimental results with respect to the subjective measurement demonstrate that the proposed metric outperforms the current methods.
75 citations