A Query Language for Exploratory Analysis of Video-Based Tracking Data in Padel Matches

Recent advances in sensor technologies, in particular video-based human detection, object tracking and pose estimation, have opened new possibilities for the automatic or semi-automatic per-frame annotation of sport videos. In the case of racket sports such as tennis and padel, state-of-the-art deep learning methods allow the robust detection and tracking of the players from a single video, which can be combined with ball tracking and shot recognition techniques to obtain a precise description of the play state at every frame. These data, which might include the court-space position of the players, their speeds, accelerations, shots and ball trajectories, can be exported in tabular format for further analysis. Unfortunately, the limitations of traditional table-based methods for analyzing such sport data are twofold. On the one hand, these methods cannot represent complex spatio-temporal queries in a compact, readable way, usable by sport analysts. On the other hand, traditional data visualization tools often fail to convey all the information available in the video (such as the precise body motion before, during and after the execution of a shot) and resulting plots only show a small portion of the available data. In this paper we address these two limitations by focusing on the analysis of video-based tracking data of padel matches. In particular, we propose a domain-specific query language to facilitate coaches and sport analysts to write queries in a very compact form. Additionally, we enrich the data visualization plots by linking each data item to a specific segment of the video so that analysts have full access to all the details related to the query. We demonstrate the flexibility of our system by collecting and converting into readable queries multiple tips and hypotheses on padel strategies extracted from the literature.

Estimating Player Positions from Padel High-Angle Videos: Accuracy Comparison of Recent Computer Vision Methods

The estimation of player positions is key for performance analysis in sport. In this paper, we focus on image-based, single-angle, player position estimation in padel. Unlike tennis, the primary camera view in professional padel videos follows a de facto standard, consisting of a high-angle shot at about 7.6 m above the court floor. This camera angle reduces the occlusion impact of the mesh that stands over the glass walls, and offers a convenient view for judging the depth of the ball and the player positions and poses. We evaluate and compare the accuracy of state-of-the-art computer vision methods on a large set of images from both amateur videos and publicly available videos from the major international padel circuit. The methods we analyze include object detection, image segmentation and pose estimation techniques, all of them based on deep convolutional neural networks. We report accuracy and average precision with respect to manually-annotated video frames. The best results are obtained by top-down pose estimation methods, which offer a detection rate of 99.8% and a RMSE below 5 and 12 cm for horizontal/vertical court-space coordinates (deviations from predicted and ground-truth player positions). These results demonstrate the suitability of pose estimation methods based on deep convolutional neural networks for estimating player positions from single-angle padel videos. Immediate applications of this work include the player and team analysis of the large collection of publicly available videos from international circuits, as well as an inexpensive method to get player positional data in amateur padel clubs.

Syntactic and Semantic Analysis for Extended Feedback on Computer Graphics Assignments

Modern computer graphics courses require students to complete assignments involving computer programming. The evaluation of student programs, either by the student (self-assessment) or by the instructors (grading) can take a considerable amount of time and does not scale well with large groups. Interactive judges giving a pass/fail verdict do constitute a scalable solution, but they only provide feedback on output correctness. In this article, we present a tool to provide extensive feedback on student submissions. The feedback is based both on checking the output against test sets, as well as on syntactic and semantic analysis of the code. These analyses are performed through a set of code features and instructor-defined rubrics. The tool is built with Python and supports shader programs written in GLSL. Our experiments demonstrate that the tool provides extensive feedback that can be useful to support self-assessment, facilitate grading, and identify frequent programming mistakes.

Randomized clinical trial of the use of glyceryl trinitrate patches to aid arteriovenous fistula maturation

BACKGROUND

Arteriovenous fistulas are critical for haemodialysis, but maturation rates remain poor. Experimental and anecdotal evidence has supported the use of transdermal glyceryl trinitrate (GTN) patches. The aim of this RCT was to determine whether use of a GTN patch aids arteriovenous fistula maturation.

METHODS

Patients referred for arteriovenous fistula formation were eligible. The GTN or placebo patch was applied immediately after surgery and left in situ for 24 h. The primary outcome measure was the change in venous diameter at 6 weeks after fistula formation. The secondary outcome measure was clinical fistula patency at 6 weeks.

RESULTS

Of 200 patients recruited (533 screened), 101 were randomized to the placebo group and 99 to the GTN group. Of these, 81 and 86 respectively completed surgery, and had follow-up data available at 6 weeks. Improvements in venous diameter were similar in the two groups: mean(s.d.) increase 2·3(1·9) mm in the placebo group compared with 2·2(1·8) mm in the GTN group (P = 0·704). The fistula failure rate did not differ significantly between the two groups: 23 per cent for placebo and 28 per cent for GTN (P = 0·596).

CONCLUSION

GTN transdermal patches used for 24 h after surgery did not improve arteriovenous fistula maturation.

REGISTRATION NUMBER

NCT01685710 (http://www.clinicaltrials.gov).

Elevated plasma lipoprotein(a) level and its association with impaired fibrinolysis in patients with antiphospholipid syndrome

OBJECTIVE

To assess the significance of lipoprotein(a) [Lp(a)], a risk factor for atherothrombosis, and its relationship with fibrinolysis in a cohort of patients with antiphospholipid syndrome (APS).

METHODS

Plasma levels of Lp(a) were measured in 68 patients with APS (42 primary, 26 secondary to systemic lupus erythematosus).

RESULTS

Elevated plasma levels of Lp(a) were found in patients with APS compared to 22 healthy controls (p = 0.0001). The significance persisted after comparing Lp(a) levels in 3 APS subgroups (arterial thrombosis, n = 37; venous thrombosis, n = 31; recurrent miscarriages, n = 24) with those of controls (p < 0.0001). Patients with APS with maximal elevation of Lp(a) showed a lower fibrinolytic activity (lower D-dimer and higher plasminogen activator inhibitor) than patients whose Lp(a) was within a normal range.

CONCLUSION

These findings suggest that Lp(a) may represent a marker of APS and that Lp(a) has a negative effect on the fibrinolytic system that might contribute to the thrombotic tendency of APS.

Thalidomide in the treatment of the cutaneous manifestations of lupus erythematosus: experience in sixteen consecutive patients

We review the efficacy, tolerability and safety of low-dose thalidomide in the treatment of refractory disfiguring rash in 16 patients with cutaneous manifestations of lupus. Rashes, which included discoid lupus erythematosus (DLE), subacute cutaneous lupus (SCLE), photosensitive malar rash and non-specific chronic erythema, were diagnosed on clinical grounds, supported by skin biopsy in 11/16 patients. Using starting doses of 50-100 mg/day, 7/16 (44%) patients gained complete or near-complete remission of skin disease and 6/16 (37%) partial remission. Three out of 16 patients failed to respond. Maximum benefit was achieved within 16 weeks in all patients. Doses of 25-50 mg/day were effective in maintaining response. Rapid relapse occurred in 6/8 (75%) patients following drug withdrawal, but the response to thalidomide in those requiring repeat courses appeared to be maintained. There was no detectable improvement in systemic disease. One patient developed symptoms of mild peripheral neuropathy which resolved on drug withdrawal. Our experience suggests that thalidomide is effective in the treatment of severe skin manifestations of lupus refractory to other treatment and can be used safely in specialist rheumatological practice.