Emil Dumic

New image-quality measure based on wavelets

We present an innovative approach to the objective quality evaluation that could be computed using the mean difference between the original and tested images in different wavelet subbands. Discrete wavelet transform (DWT) subband decomposition properties are similar to human visual system characteristics facilitating integration of DWT into image-quality evaluation. DWT decomposition is done with multiresolution analysis of a signal that allows us to decompose a signal into approximation and detail subbands. DWT coefficients were computed using reverse biorthogonal spline wavelet filter banks. Wavelet coefficients are used to compute new image-quality measure (IQM). IQM is defined as perceptual weighted difference between coefficients of original and degraded image.

VCL@FER Image Quality Assessment Database

In this paper we present new image quality database which consists of four degradation types: JPEG, JPEG2000, White noise and Gaussian blur. Results for five commonly used objective quality measures are compared using newly developed image database, as well as LIVE image database.

IQM2: new image quality measure based on steerable pyramid wavelet transform and structural similarity index

In this paper, we present a new full-reference objective image quality measure—IQM2, based on structural similarity index and steerable pyramid wavelet transform. IQM2 is tested using different number of orientation kernels and seven subjective databases. Finally, IQM2 measure is compared with twelve commonly used full-reference objective measures. Results show that proposed IQM2 measure, using kernel with 2 orientations, provides good correlation with the results of subjective evaluation while keeping computational time lower than other similar performing objective measures.

Comparison of HDTV formats by objective video quality measures

In this paper we compare some of the objective quality measures with subjective, in several HDTV formats, to be able to grade the quality of the objective measures. Also, comparison of objective and subjective measures between progressive and interlaced video signal will be presented to determine which scanning emission format is better, even if it has different resolution format. Several objective quality measures will be tested, to examine the correlation with the subjective test, using various performance measures.

Bilateral Asymmetry Detection in Digital Mammography Using B-Spline Interpolation

Digital mammography allows detection of breast abnormalities in early stage of breast cancer development. One of the abnormalities that may indicate breast cancer in its early stage is bilateral asymmetry. This paper presents computer-aided detection algorithm for bilateral asymmetry that uses B-spline interpolation for breast alignment. Alignment of the right and left breast is important step in computer-aided detection algorithm in order to allow comparison of corresponding points in right and left breast. Differential analysis of breasts is based on simple subtraction technique. The results are highlighted with color in each image and presented on a computer monitor thereby indicating radiologist the regions that need to have a second look and be further investigated. We found that our approach can be a very useful tool for radiologists in detection and diagnosis of bilateral asymmetry.

Evaluation of Transmission Channel Models Based on Simulations and Measurements in Real Channels

This paper presents simulation environment that includes transmission channel models from the ETSI standard EN 300 744 (DVB-T system) and channel models based on real measured parameters. Our simulation includes transmitter and receiver, supports different system parameters (modulation, code rate, guard interval) and channel models. It is adaptive and reconfigurable environment that allows incorporation of hardware generated channel matrix in channel model and provides accurate estimation of system constraints. The model offers evaluation of channel models and can be used for testing and educational purposes.

3D video subjective quality: a new database and grade comparison study

This paper presents a research study on the subjective assessment of 3D video quality using a newly constructed 3D video database (3DVCL@FER). This database consists of 8 original 3D video sequences, each degraded with 22 different degradation types, including degradations specific to stereoscopic systems. The subjective assessment was done with the support of a purpose-built easily customizable grade collection platform and conducted in two research laboratories, in Croatia and Portugal. Subjective scores for quality, depth and comfort were collected and DMOS (Difference Mean Opinion Score) values were calculated. Different objective measures (for image, 3D image, 2D video and 3D video) were separately compared with DMOS values for quality, depth and comfort. The 3D video grade-annotated database described is publicly accessible and can be used in research-related activities like assessment of existing objective measures, using the entire database or parts of it, and construction of new objective measures specific to 3D video degradations. The system presented can also be used to collect and compare subjective quality grades originating from different sites to study the effect of different observation conditions and observer/graders populations on the DMOS quality values for 3D video depth and comfort.

Subjective quality assessment of H.265 versus H.264 Video Coding for High-Definition Video Systems

This paper gives our findings on subjective assessment of H.265 versus H.264 Video Coding for High-Definition Video Systems. For the purposes of our research a database consisting of 4 original HD video sequences was prepared with 30 degraded HD video sequences each, with various compression steps both in H.265/HEVC and H.264/AVC. The subjective assessment was conducted in one research laboratory in Croatia. The aim of this paper is to compare results obtained for H.265 versus H.264 Video Coding and to assess the performance of both standards. This assessment will help in the future decision on the coding standard that is going to be used in DVB-T2 networks in Croatia. Additionally, a status of the preparation activities for the allocation of the second digital dividend band in Croatia is given and further developments are described.

Benchmark of state of the art objective measures for 3D stereoscopic video quality assessment on the Nantes database

In this work we present a study on the performance of existing state of the art 2D objective image and video quality measures, tested on the new 3D stereoscopic video NAMA3DS1-COSPAD1 database. Different image and video quality measures have been tested on test material affected by different types of degradations. Results show that in some cases, image quality measures give better results than video quality measures. This paradoxical result means that more effort should be devoted to designing new 3D video quality assessment measures. The results presented and accompanying discussion can be used to motivate and guide future research directed towards definition of effective new 3D stereoscopic video quality measures.

Hidden influences on image quality when comparing interpolation methods

When comparing different interpolation methods, common approach is to use an objective image quality measure that evaluates the numerical errors between the original image and interpolated image. The problem with this approach is impossibility to have original image in two or more different resolutions. Common method is to start with an original image, calculate a lower resolution version of original image (downscaling), and then use different interpolation methods to magnify low resolution image (upscaling). After that original and magnified interpolated images are compared to evaluate difference between them. In our research we found that downscaling process has great influence on results of upscaling. This influence is not properly addressed in references that deal with image interpolation methods. Therefore in this paper we will try to examine how the process of achieving lower resolution image affects picture quality of interpolated images. Our results show that comparison of image interpolation methods depends on downscaling technique, image contents and quality metric.