Multi-decoder dprnn: Source separation for variable number of speakers

We propose an end-to-end trainable approach to singlechannel speech separation with unknown number of speakers. Our approach extends the MulCat source separation backbone with additional output heads: A count-head to infer the number of speakers, and decoder-heads for reconstructing the original signals. Beyond the model, we also propose a metric on how to evaluate source separation with variable number of speakers. Specifically, we clear up the issue on how to evaluate the quality when the ground-truth has more or less speakers than the ones predicted by the model. We evaluate our approach on the WSJ0-mix datasets, with mixtures up to five speakers. We demonstrate that our approach outperforms state-of-the-art in counting the number of speakers and remains competitive in quality of reconstructed signals.