Piecewise constant nonnegative matrix factorization

In this paper we propose a non-negative matrix factorization (NMF) model with piecewise-constant activation coefficients. This structure is enforced using a total variation penalty on the rows of the activation matrix. The resulting optimization problem is solved with a majorization-minimization procedure. The proposed algorithm is well suited to analyze data explained by underlying piecewise-constant sequences of states. Its properties are first illustrated using synthetic data. We then use it to solve a video structuring problem that involves both segmentation and clustering tasks. An improvement over a state-of-the-art temporally smoothed NMF algorithm of both clustering and segmentation quality measures is observed.