Exploring the Potential of VAE Decoders for Enhanced Speech Re-Synthesis

In this paper, we study different Variational Autoencoders (VAEs) decoder distributions in the audio setting to see how to improve magnitude and phase reconstruction on speech resynthesis tasks. We first provide background on the existing decoder distributions, such as Complex Gaussian and Laplace, which are equivalent to a Gamma decoder under certain conditions. We then consider separately modeling speech’s magnitude and phase information to see if we can improve the quality of either component, yielding an improvement in speech resynthesis. Extensive experiments show the Gamma decoder significantly improves magnitude reconstruction and that the von Mises decoder can weakly learn phase information. The novel Gamma decoder outperforms previous approaches, achieving a near-perfect PESQ of 4.4, representing a 42% improvement upon the state-of-the-art IS-VAE and an 86% decrease in the FAD metric. Our results demonstrate the effectiveness of the novel approach, improving the quality of speech resynthesis and compression capacity of VAEs.