Snježana Rimac-Drlje

Objective video quality metrics

This paper discusses methods used in different objective video quality metrics. An experimental comparison of different objective methods is also conducted. This experiment shows the importance of video content for a subjective quality evaluation not comprised well by the objective metrics used.

Review of objective video quality metrics and performance comparison using different databases

The use of video-based applications has increased in recent years owing to the development of video technology as well as the widespread use of the Internet. Thus the evaluation of perceptual video quality has become very important and numerous video quality assessment (VQA) metrics have been developed over the past years. In this paper, we give a classification and a short review of objective VQA metrics, with a focus on the full reference metrics. With the aim of conducting a reliable test of the VQA metrics performances, we made two databases, each of them including 90 distorted video sequences. We carried out a subjective quality evaluation on these databases and the data were made available to the research community. Furthermore, we compared the performance of nine different, freely available, objective VQA metrics by using three different databases in different resolutions: LIVE Video Quality Database (768x432 resolution) and our two newly created databases for progressively scanned videos, i.e. ETFOS CIF Video Quality (ECVQ) database and ETFOS VGA Video Quality (EVVQ) database. Five different distortion types were used and the total number of 330 video sequences was evaluated. A comparison of metrics was done with respect to accuracy, monotonicity, stability, as well as complexity vs. accuracy criteria. The results show that the resolution, the content of the sequence and the distortion type have a significant influence on the performances of VQA metrics. Metrics that generally achieve a high correlation with subjective results for all databases and all distortion types are MOtion-based Video Integrity Evaluation (MOVIE) and Foveated Mean Squared Error (FMSE), but MOVIE has significantly higher complexity than FMSE. An exception is the distortion caused by IP transmission for which none of the analyzed metrics has shown satisfying accuracy and stability.

Subjective and objective quality evaluation of the H.264/AVC coded video

The H.264/AVC codec provides a superior coding efficiency and an improved network adaptation if compared to older video standards. In this paper we present experimental results obtained by the subjective and objective quality evaluation of the H.264/AVC coded video. Four objective metrics are used: peak signal-to-noise ratio (PSNR), minimum of locally averaged PSNR (local_PSNR), video quality metric (VQM) and structural similarity index (SSIM). We have analyzed results of objective and subjective metrics for several CIF sequences and bit rates. Also, we have compared results obtained for H.264/AVC coded sequences with those coded with MPEG-4 Part 2 codec. Results of the subjective quality evaluation show that on the bit rates below 640 kb/s the H.264/AVC codec has achieved an obviously higher video quality, ensured by the objective metrics as well. On the bit rates higher than 640 kb/s the subjective quality of sequences coded by MPEG-4 Part 2 is close to the quality of H.264/AVC coded video, confirmed only by the SSIM and local_PSNR results.

Comparison of H.264/AVC and MPEG-4 part 2 coded video

brief overview of H.264/AVC and MPEG-4 Part 2 standards is given in this paper with focus on differences between them. Experimental quality comparison of H.264/AVC and MPEG-2 Part 2 coded video is done for several sequences and bit rates. The codecs used in the experiment are JVT JM ver. 10.2, as implementation of H.264/AVC, andXviD ver. 1.1.0, as implementation of MPEG-4 Part 2. The peak signal-to-noise ratio (PSNR) and video quality model (VQM) are used as objective quality metrics. The results obtained show that JVT JM codec outperforms XviD codec both in objective and subjective quality.

Neural network based detection of defects in texture surfaces

In this article we present an algorithm for automatic detection of surface defects on ceramic tiles. This algorithm is based on the probabilistic neural network with radial basis. To improve sensitivity of the detection procedure an image of the tile is divided into segments and one neural network is made for each segment. The discrete wavelet transform (DWT) is used for the feature extraction in every segment. Maximums of the wavelet coefficients as well as the mean value of the approximation coefficients form an input vector for the neural network. Experimental results of the defect detection for different types of tiles and with different parameters of the algorithm show a high sensitivity and applicability of the proposed procedure.

Applications classification and QoS requirements

The applications and network services are key points that could provide the user the necessary quality of service. It is very hard to definitely divide the applications and the underlying services to uniquely describe the application and the service classes. This paper tries to comprise different classes of applications into a unique classification. Different standpoints and criteria are included and evaluated The QoS requirements for every defined application class are defined and described. Finally, on the basis of the introduced classification the required service classes for serving such classes are defined.

Broadband ecosystem elements in techno-economic modelling and analysing of broadband access solutions for rural areas

Encouraged by broadband development initiatives and strategies that aim at the reduction of the existing digital divide between rural and urban European areas by the year 2020, the current situation in the case study of Croatian rural broadband market is analysed, and the possibilities for further broadband Internet access implementation in rural areas are highlighted in the paper within the context of broadband ecosystem elements analysis. Furthermore, in order to address the exisiting digital divide problem, an extended techno- economic modelling process for rural broadband Internet access implementation analyses is proposed. The proposed additional part of model serves as an upgrade for the standard techno- economic models and allows a detailed analysis of the specificities of different rural areas, based on the available data. Finally, the efficiency of the proposed model’s application when choosing the best business strategies for different fixed and mobile, wired and wireless broadband access solutions in rural areas is presented.

Foveation-based content adaptive root mean squared error for video quality assessment

When the video is compressed and transmitted over heterogeneous networks, it is necessary to ensure the satisfying quality for the end user. Since human observers are the end users of video applications, it is very important that the human visual system (HVS) characteristics are taken into account during the video quality evaluation. This paper deals with video quality assessment (VQA) based on HVS characteristics and proposes a novel full-reference (FR) VQA metric called the Foveation-based content Adaptive Root Mean Squared Error (FARMSE). FARMSE uses several HVS characteristics that significantly influence perception of distortions in a video. Primarily these are foveated vision, reduction of the spatial acuity due to motions as well as spatial masking. Foveated vision is related to variable resolution of HVS across the viewing field, where the highest resolution is at the point of fixation. The point of fixation is projected onto the fovea – the area of retina with the highest density of photoreceptors. The part of image that falls on fovea is perceived by the highest acuity, whereas the spatial acuity decreases as the distance of the image part from the fovea increases. Spatial acuity further decreases if eyes cannot track moving objects. Both mentioned mechanisms influence contrast sensitivity of the HVS. Contrast sensitivity is frequency dependent and FARMSE uses Haar filters to utilize this dependence. Furthermore, spatial masking is implemented in each frequency channel. The FARMSE performance is compared to this of nine state-of-the-art VQA metrics on two different databases, LIVE and ECVQ. Additionally, the metrics are compared in terms of calculation complexity. The performed experiments show that FARMSE achieves high performance when predicting the quality of videos with different resolutions, degradation types and content types. FARMSE results outperform the results of most of the analyzed metrics, whereas they are comparable to these of the best publicly available metrics, including the well-known MOtion-based Video Integrity Evaluation (MOVIE) index. Besides that, FARMSE calculation complexity is significantly lower than that of the metrics comparable thereto in terms of prediction accuracy.

Fast frame-rate up-conversion method for video enhancement

In this paper a new frame-rate up-conversion (FRUC) method is presented. To obtain an algorithm with a low level of complexity we used the block matching technique and fast subpixel motion estimation by Taylor series. Frame interpolation is made by combination of forward and backward prediction. Furthermore, for frames with a low temporal activity, the motion estimation is skipped and simple averaging of the previous and following frames makes the frame interpolation. Quality of the interpolated frames is compared according to PSNR results obtained for proposed and two more complex FRUC methods. Proposed method shows comparable results for all tested video sequences except for the sequences with a high level of motion.

Ultra-wideband systems with orthogonal coded differential TR receiver

This paper presents coded differential TR (cDTR) receiver that transmits extra bit by mapping information in K different orthogonal codes. The performance of the coded DTR is analyzed and compared with the conventional DTR. Throughout the analysis, the performance of receivers in terms of bit error probability (BEP), data rate and receiver complexity are assessed. The results show that coded DTR is able to outperform conventional DTR receiver in terms of data rate maintaining the same BEP. Additionally, the receiver hardware complexity issue is discussed