Browsing by Author "Monteiro, Ricardo"
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- Career Planning in Elite Soccer: The Mediating Role of Self-Efficacy, Career Goals, and Athletic IdentityPublication . Monteiro, Ricardo; Monteiro, Diogo; Torregrossa, Miquel; Travassos, BrunoThis study proposed a model to examine the role of self-efficacy, career goals, and athletic identity (AI) on the career planning of elite soccer players. Two hundred and eighty-one elite soccer players (males) participated in this study. Means, SD, and bivariate correlations were calculated for the variables under analysis. The hypothesized effect of self-efficacy, career goals, and AI on career planning was tested using structural equation modeling (SEM). Results supported the adequacy of the proposed model in explaining the career planning. Career planning is positively influenced by the level of self-efficacy of players through the definition of career goals and is negatively influenced by the level of AI. At the same time, the self-efficacy of players through the definition of career goals positively influenced AI. These findings reinforce the important role of self-efficacy and career goals for the development of AI and career planning and at the same time the opposite relationship between AI and career planning. Thus, it is suggested that a balance on AI, maintaining high levels of self-efficacy and career goals, is required to improve the process of career planning and retirement
- Light field HEVC-based image coding using locally linear embedding and self-similarity compensated predictionPublication . Monteiro, Ricardo; Lucas, Luis; Conti, Caroline; Nunes, Paulo; M. M. Rodrigues, Nuno; Faria, Sergio; Pagliari, Carla; Silva, Eduardo da; Soares, LuisLight field imaging is a promising new technology that allows the user not only to change the focus and perspective after taking a picture, as well as to generate 3D content, among other applications. However, light field images are characterized by large amounts of data and there is a lack of coding tools to efficiently encode this type of content. Therefore, this paper proposes the addition of two new prediction tools to the HEVC framework, to improve its coding efficiency. The first tool is based on the local linear embedding-based prediction and the second one is based on the self-similarity compensated prediction. Experimental results show improvements over JPEG and HEVC in terms of average bitrate savings of 71.44% and 31.87%, and average PSNR gains of 4.73dB and 0.89dB, respectively.
- Light field image coding: objective performance assessment of Lenslet and 4D LF data representationsPublication . Monteiro, Ricardo; M. M. Rodrigues, Nuno; Faria, Sergio; Nunes, paulo; Tescher, Andrew G.State-of-the-art light field (LF) image coding solutions, usually, rely in one of two LF data representation formats: Lenslet or 4D LF. While the Lenslet data representation is a more compact version of the LF, it requires additional camera metadata and processing steps prior to image rendering. On the contrary, 4D LF data, consisting of a stack of sub-aperture images, provides a more redundant representation requiring, however, minimal side information, thus facilitating image rendering. Recently, JPEG Pleno guidelines on objective evaluation of LF image coding defined a processing chain that allows to compare different 4D LF data codecs, aiming to facilitate codec assessment and benchmark. Thus, any codec that does not rely on the 4D LF representation needs to undergo additional processing steps to generate an output comparable to a reference 4D LF image. These additional processing steps may have impact on the quality of the reconstructed LF image, especially if color subsampling format and bit depth conversions have been performed. Consequently, the influence of these conversions needs to be carefully assessed as it may have a significant impact on a comparison between different LF codecs. Very few in-depth comparisons on the effects of using existing LF representation have been reported. Therefore, using the guidelines from JPEG Pleno, this paper presents an exhaustive comparative analysis of these two LF data representation formats in terms of LF image coding efficiency, considering different color subsampling formats and bit depths. These comparisons are performed by testing different processing chains to encode and decode the LF images. Experimental results have shown that, in terms of coding efficiency for different color subsampling formats, the Lenslet LF data representation is more efficient when using YUV 4:4:4 with 10 bit/sample, while the 4D LF data representation is more efficient when using YUV 4:2:0 with 8 bit/sample. The “best” LF data representation, in terms of coding efficiency, depends on several factors which are extensively analyzed in this paper, such as the objective metric that is used for comparison (e.g., average PSNR-Y or average PNSR-YUV), the type of LF content, as well as the color format. The maximum objective quality is also determined, by evaluating the influence of each block from each processing chain in the objective quality of the reconstructed LF image. Experimental results show that, when the 4D LF data representation is not used the maximum achieved objective quality is lower than 50 dB, in terms of average PSNR-YUV.
- Modeling athletic career of football players: Implications for career management and retirementPublication . Monteiro, Ricardo; Monteiro, Diogo; Torregrossa, Miquel; Travassos, BrunoThis study aimed to identify Career Indicators (CIs) over the stages of career development (Initiation/Development, Mastery, and Discontinuation stages) in the retirement stage of Portuguese football players. Three thousand five hundred retired Portuguese football players that played between 1960 and 2018 were considered in this study. A path analysis was performed to identify the standardized direct and indirect effects of the CI at each stage of career development, on Portuguese football players’ retirement age. The proposed model highlighted that the relationship between the CI number of seasons as a youth player, number of seasons as a youth player in top 3 clubs, age of first registration as a senior player, number of seasons as a senior player, number of seasons as a senior player in top 3 clubs, number of total games as a senior player, age of the last best result age achieved, number of games in the retirement season, and discontinuation stage length contribute to explain 40% of the retirement age of Portuguese football players. Results allowed the understanding of the influence of each stage of career development on career length. According to the Holistic Athletic Career Model, it was the first attempt to create a predictive model of CI of athletic variables. Further research should be developed to incorporate some mediator variables such as players’ performance levels and achievement to improve the explanation of the development of football players’ careers and retirement.