Providing Meaningful Alignments for Periodic Signs

In sign languages, a periodic sign is one that contains repeated movements. Dynamic Time Warping (DTW) is often used in sign language recognition to generate a frame alignment between two input signs that provides a measure of their similarity. Alignments provided by DTW may not be meaningful when the input contains periodic signs, especially when the number of periods differs between inputs. Additionally, the number of periods may change between individual signers and signs. Little work has been done to address the problem of recognizing periodic signs in the context of DTW. This work evaluates two DTW-based approaches. The first uses a newly defined periodic warping path. The second uses manual annotations to truncate periodic input to contain no more than two periods. These two methods are compared against a standard implementation of DTW. Recognition accuracy and quality of alignment are analyzed. The results motivate a need for further research in periodic sign language recognition.