Seon-Oh Lee

Real-time objective quality assessment based on coding parameters extracted from H.264/AVC bitstream

In this paper, we propose a new method for objective video quality assessment from coding parameters of an H.264/AVC bitstream as a hybrid/bitstream category. Conventional image and video quality assessment methods evaluate image or video quality using a degraded video or image after fully decoding it. On the other hand, the proposed method assesses video quality not with reconstructed videos but using coding parameters extracted from a bitstream. The parameters can be easily extracted while decoding the H.264/AVC bitstream. To assess video quality, the proposed algorithm is based on statistics of boundary strengths (BS), quantization parameters (QP), and average bitrates. Accuracy of the proposed method is 9.7% higher than those of the conventional algorithms in terms of Pearson correlation. Furthermore, the proposed method has significantly lower computational complexity than the conventional methods.

New Full-Reference Visual Quality Assessment Based on Human Visual Perception

This paper presents an objective video quality evaluation method for quantifying the subjective quality of digital mobile videos. The proposed method aims to objectify the subjective quality by extracting edge region features and blockiness parameters. To evaluate the proposed algorithms performance, we carried out subjective video quality tests with the double-stimulus continuous quality scale (DSCQS) method and obtained differential mean opinion score (DMOS) values for 140 video clips (CIF/QCIF). We then compared the proposed methods performance to that of existing methods in terms of DMOS estimation accuracy. Experimental results show that the proposed method is approximately 25% better than the EPSNR method in estimating actual DMOS values.

Objectification of perceptual image quality for mobile video

This paper presents an objective video quality evaluation method for quantifying the subjective quality of digital mobile video. The proposed method aims to objectify the subjective quality by extracting edgeness and blockiness parameters. To evaluate the performance of the proposed algorithms, we carried out subjective video quality tests with the double-stimulus continuous quality scale method and obtained differential mean opinion score values for 120 mobile video clips. We then compared the performance of the proposed methods with that of existing methods in terms of the differential mean opinion score with 120 mobile video clips. Experimental results showed that the proposed methods were approximately 10% better than the edge peak signal-to-noise ratio of the J.247 method in terms of the Pearson correlation.

Hybrid bitstream-based video quality assessment method for scalable video coding

We propose a quality assessment method from decoding parameters of compressed bitstreams by scalable video coding (SVC) as a hybrid/bitstream category. Conventional video quality assessment methods evaluate the video quality of degraded videos after full reconstruction. However, the proposed assessment method quantifies video quality of SVC not only with reconstructed videos for the base layer but also with decoding parameters for the enhancement layer. The proposed algorithm assesses the enhanced quality degree of the enhancement layers with statistics of various coding parameters for the enhancement layers with respect to the quality of the base layer. The accuracy of the proposed algorithm is 23% higher than those of conventional algorithms in terms of Pearson correlation. Furthermore, the proposed algorithm has significantly lower computational complexity than conventional methods.

Sample Adaptive Offset Parallelism in HEVC

We propose a parallelization method for SAO, in-loop filter of HEVC. SAO filtering proceeds along CTB lines and there exists data dependency between inside and outside of CTB boundaries. Data dependency makes data-level parallelization hard. In this paper, we equally divided an entire frame into sub regions. With a little amount of memory, proposed method shows 1.9 times of performance enhancement in terms of processing time.

No-reference peak signal to noise ratio estimation based on generalized Gaussian modeling of transform coefficient distributions

We present a no-reference peak signal to noise ratio (PSNR) estimation algorithm based on discrete cosine transform (DCT) coefficient distributions from H.264/MPEG-4 part 10 advanced video codec (H.264/AVC) bitstreams. To estimate the PSNR of a compressed picture without the original picture on the decoder side, it is important to model the distribution of transform coefficients obtained from quantized coefficients accurately. Whereas several conventional algorithms use the Laplacian or Cauchy distribution to model the DCT coefficient distribution, the proposed algorithm uses a generalized Gaussian distribution. Pearsons χ 2 (chi-square) test was applied to show that the generalized Gaussian distribution is more appropriate than the other models for modeling the transform coefficients. The χ 2 test was also used to find optimum parameters for the generalized Gaussian model. It was found that the generalized Gaussian model improves the accuracy of the DCT coefficient distribution, thus reducing the mean squared error between the real and the estimated PSNR.

Control of High Pretilt Angle in NLC, 5CB, by the Washing Process on a Polyimide Surface with CF3 Moieties

The washing effects on pretilt angle generation in a nematic liquid crystal (NLC), 4-n-pentyl-4′-cyanobiphenyl (5CB) on a rubbed polyimide (PI) surface with trifluoromethyl moiety have been successfully studied. The pretilt angle of 5CB is increased by the washing process on the rubbed PI surface. The surface tension on the rubbed PI surface increases with the rubbing strength RS and then saturated above RS = 150 mm. The pretilt angle of 5CB for all washing processes on the rubbed PI surface decreases with the surface tension. We have found that the pretilt angle of 5CB on the rubbed PI surface may be attributed van der walls (VDW) dispersion interaction between the LC molecules. and the polymer surfaces having trifluoromethyl moieties.