Human gesture classification by brute-force machine learning for exergaming in physiotherapy

In this paper, a novel approach for human gesture classification on skeletal data is proposed for the application of exergaming in physiotherapy. Unlike existing methods, we propose to use a general classifier like Random Forests to recognize dynamic gestures. The temporal dimension is handled afterwards by majority voting in a sliding window over the consecutive predictions of the classifier. The gestures can have partially similar postures, such that the classifier will decide on the dissimilar postures. This brute-force classification strategy is permitted, because dynamic human gestures show sufficient dissimilar postures. Online continuous human gesture recognition can classify dynamic gestures in an early stage, which is a crucial advantage when controlling a game by automatic gesture recognition. Also, ground truth can be easily obtained, since all postures in a gesture get the same label, without any discretization into consecutive postures. This way, new gestures can be easily added, which is advantageous in adaptive game development. We evaluate our strategy by a leave-one-subject-out cross-validation on a self-captured stealth game gesture dataset and the publicly available Microsoft Research Cambridge-12 Kinect (MSRC-12) dataset. On the first dataset we achieve an excellent accuracy rate of 96.72%. Furthermore, we show that Random Forests perform better than Support Vector Machines. On the second dataset we achieve an accuracy rate of 98.37%, which is on average 3.57% better then existing methods

Human action recognition using hierarchic body related occupancy maps

This paper introduces a novel spatial method for human action recognition that is discriminative without needing temporal information or action key poses. First, skeletal data is acquired with the Microsoft Kinect v2 sensor and undergoes a Pose Invariant Normalization (PIN) process. The PIN process translates, rotates and scales the various observed poses to eliminate body differences and positional differences between subjects. Second, the method uses a Body Related Occupancy Map (BROM), that describes in a 3D grid how the area around specific body parts is used, as a strong indicator of the particular action that is being performed. The BROM and its 2D projections are used as feature inputs for Random Forest classifiers. These classifiers are then combined in a hierarchic structure to boost the classification performance. The approach is tested on a self-captured database of 23 human actions for game-play. On this database a classification with an accuracy score of 91% is achieved for the hierarchic BROM (HiBROM) classification. On the public CAD60 dataset, the HiBROM classifier attains 87.2% accuracy which is comparable to other state-of-the-art methods

Foreground background segmentation in front of changing footage on a video screen

In this paper, a robust approach for detecting foreground objects moving in front of a video screen is presented. The proposed method constructs a background model for every image shown on the screen, assuming these images are known up to an appearance transformation. This transformation is guided by a color mapping function, constructed in the beginning of the sequence. The foreground object is then segmented at runtime by comparing the input from the camera with a color mapped representation of the background image, by analysing both direct color and edge feature differences. The method is tested on challenging sequences, where the background screen displays photo-realistic videos. It is shown that the proposed method is able to produce accurate foreground masks, with obtained F1-scores ranging from 85.61% to 90.74% on our dataset