Estimation of inter-channel phase differences using non-negative matrix factorization

Estimation of non-linearities in phase differences between two or more channels of an audio recording leads to a more precise spatial information in audio signal enhancement applications. In this work, we propose the estimation of these non-linearities in multi-channel, multi-source audio mixtures in reverberant environments. For this task, we compute short term cross-correlation functions between the channels and extract the non-linear inter-channel phase differences as well as a measure of activation for each source. This is conducted by decomposition of the cross-correlation matrix using a non-negative matrix factorization method. Our evaluation shows that the estimated inter-channel phase differences depict the non-linearities. Furthermore, the estimated activations reflect the time instances where the sources are active. In audio source separation experiments the proposed method outperforms a state-of-the-art approach based on linear phase differences by 30% in terms of relative improvement.