scholarly journals A rate control technique for off line H.264/AVC video coding using subjective quality of video

2008 ◽  
Vol 54 (3) ◽  
pp. 1465-1472 ◽  
Author(s):  
S.L.P. Yasakethu ◽  
W.A.C. Fernando ◽  
S. Adedoyin ◽  
A. Kondoz
Keyword(s):  
Video Coding ◽  
Rate Control ◽  
Subjective Quality ◽  
Control Technique

scholarly journals Basic Unit Layer Rate Control Algorithm for H.264 Based on Human Visual System

2013 ◽  
Vol 2013 ◽  
pp. 1-6
Author(s):  
Xiao Chen ◽  
Haiying Liu
Keyword(s):  
Rate Control ◽  
Signal To Noise Ratio ◽  
Subjective Quality ◽  
Basic Unit ◽  
Motion Feature ◽  
Original Algorithm ◽  
Unit Layer ◽  
Rate Control Algorithm ◽  
Visual Characteristic

In the process of the video coding, special attention should be paid to the subjective quality of the image. In the JVT-G012 algorithm for H.264, the influence of the human visual characteristic in basic unit layer rate control was not taken into account. This paper takes the influence of the human visual characteristic into the full consideration and offers ways to improve the subjective quality of the image. The visual characteristic factor, which is constituted by the motion feature and edge feature, is used to reasonably allocate the target bits, and then its quantization parameter is adjusted by encoded frame information. The experimental results show that, in comparison to the original algorithm, the proposed algorithm can not only control the bit rate more accurately but also make the peak signal to noise ratio (PSNR) stable, so as to improve the stationarity of the video image. The subjective quality of the reconstructed video is more satisfying.

scholarly journals A Novel Two-Level Rate Control Algorithm Based on Visual Attention for 360-Degree Video for Versatile Video Coding Standard

2020 ◽  
Author(s):  
Hoda Roodaki
Keyword(s):  
Visual Attention ◽  
Video Coding ◽  
Rate Control ◽  
Control Algorithm ◽  
Perceptual Quality ◽  
Motion Models ◽  
Proper Number ◽  
Rate Control Algorithm ◽  
Motion Complexity

Abstract 360-degree video is providing users with an interactive experience to explore the scenes freely. But, because only a small portion of the entire video, called viewport, is watched at every point in time, transmitting the entire video is bandwidth-consuming. Since, the perceptual quality of such video mainly depends on the quality of the viewport, more bandwidth should be assigned to these important parts of the scene. Hence, understanding how people observe and explore 360-degree content is essential. In this paper, we propose a new Two-level rate control algorithm which tries to allocate more bits for encoding the viewport parts of a 360-degree video. The head and eye movements of the observers is used to investigate the visual attention of people to detect the viewports. Then, a Coding Tree Unit (CTU) level rate assignment approach is proposed to assign a proper number of bits to each CTU of the viewport and non-viewport parts. It is assumed that higher motion complexity results in higher bitrates of the encoded video. So, we propose to assign the proper number of bits to each CTU according to its motion complexity. Another novel part of our proposed approach is proposing a new metric to parameterize the motion complexity of each CTU using the high-order motion models in Versatile Video Coding (VVC) standard. Experimental results show that our proposed rate control, on average, achieves 58.27% reduction in bitrate in the Bjøntegaard-Bitrate scales, compared to the standard VCC standard. Furthermore, the proposed scheme provides a significantly better subjective viewing quality compared to the-state-of-the-art methods.

A Novel Rate Control Technique for Multiview Video Plus Depth Based 3D Video Coding

2011 ◽  
Vol 57 (2) ◽  
pp. 562-571 ◽  
Author(s):  
Yanwei Liu ◽  
Qingming Huang ◽  
Siwei Ma ◽  
Debin Zhao ◽  
Wen Gao ◽  
...  
Keyword(s):  
Video Coding ◽  
Rate Control ◽  
3D Video ◽  
Control Technique ◽  
Multiview Video ◽  
3D Video Coding

scholarly journals A Novel Macroblock Level Rate Control Method for Stereo Video Coding

2014 ◽  
Vol 2014 ◽  
pp. 1-11 ◽  
Author(s):  
Gaofeng Zhu ◽  
Mei Yu ◽  
Gangyi Jiang ◽  
Zongju Peng ◽  
Feng Shao ◽  
...  
Keyword(s):  
Video Coding ◽  
Rate Control ◽  
Control Method ◽  
Bit Allocation ◽  
Stereo Video ◽  
Left And Right ◽  
Four Levels ◽  
Level Group ◽  
Binocular Perception

To compress stereo video effectively, this paper proposes a novel macroblock (MB) level rate control method based on binocular perception. A binocular just-notification difference (BJND) model based on the parallax matching is first used to describe binocular perception. Then, the proposed rate control method is performed in stereo video coding with four levels, namely, view level, group-of-pictures (GOP) level, frame level, and MB level. In the view level, different proportions of bitrates are allocated for the left and right views of stereo video according to the prestatistical rate allocation proportion. In the GOP level, the total number of bitrates allocated to each GOP is computed and the initial quantization parameter of each GOP is set. In the frame level, the target bits allocated to each frame are computed. In the MB level, visual perception factor, which is measured by the BJND value of MB, is used to adjust the MB level bit allocation, so that the rate control results in line with the human visual characteristics. Experimental results show that the proposed method can control the bitrate more accurately and get better subjective quality of stereo video, compared with other methods.

Cognitive determinants of community functioning and quality of life in homeless adults with mental illness: 6-year follow-up from the At Home/Chez Soi Study Toronto site

2021 ◽  
pp. 1-9
Author(s):  
K. M. Gicas ◽  
C. Mejia-Lancheros ◽  
R. Nisenbaum ◽  
R. Wang ◽  
S. W. Hwang ◽  
...  
Keyword(s):  
Quality Of Life ◽  
Mental Health ◽  
Functional Outcomes ◽  
Verbal Learning ◽  
Subjective Quality ◽  
Subjective Quality Of Life ◽  
Homeless Adults ◽  
Community Functioning ◽  
At Home

Abstract Background High rates of physical and mental health comorbidities are associated with functional impairment among persons who are homeless. Cognitive dysfunction is common, but how it contributes to various functional outcomes in this population has not been well investigated. This study examines how cognition covaries with community functioning and subjective quality of life over a 6-year period while accounting for the effects of risk and protective factors. Methods Participants were 349 homeless adults (mean age = 39.8) recruited from the Toronto site of the At Home/Chez Soi study, a large Canadian randomized control trial of Housing First. Participants completed up to four clinical evaluations over 6 years. Factor scores were created to index verbal learning and memory (vLM) and processing speed-cognitive flexibility (PSCF). The primary outcomes were community functioning and subjective quality of life. Risk factors included lifetime homelessness, mental health diagnoses, medical comorbidity, and childhood adversity. Linear mixed-effects models were conducted to examine cognition-functional outcome associations over time, with resilience as a moderator. Results Better vLM (b = 0.787, p = 0.010) and PSCF (b = 1.66, p < 0.001) were associated with better community functioning, but not with quality of life. Resilience conferred a protective effect on subjective quality of life (b = 1.45, p = 0.011) but did not moderate outcomes. Conclusions Our findings suggest a need to consider the unique determinants of community functioning and quality of life among homeless adults. Cognition should be prioritized as a key intervention target within existing service delivery models to optimize long-term functional outcomes.

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