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arXiv · 2303.12984

LMCodec: A Low Bitrate Speech Codec With Causal Transformer Models

Teerapat Jenrungrot·Michael Chinen·W. Bastiaan Kleijn·Jan Skoglund·Zalán Borsos·Neil Zeghidour·Marco Tagliasacchi
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Abstract

We introduce LMCodec, a causal neural speech codec that provides high quality audio at very low bitrates. The backbone of the system is a causal convolutional codec that encodes audio into a hierarchy of coarse-to-fine tokens using residual vector quantization. LMCodec trains a Transformer language model to predict the fine tokens from the coarse ones in a generative fashion, allowing for the transmission of fewer codes. A second Transformer predicts the uncertainty of the next codes given the past transmitted codes, and is used to perform conditional entropy coding. A MUSHRA subjective test was conducted and shows that the quality is comparable to reference codecs at higher bitrates. Example audio is available at https://mjenrungrot.github.io/chrome-media-audio-papers/publications/lmcodec.

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Teerapat Jenrungrot, Michael Chinen, W. Bastiaan Kleijn, Jan Skoglund, Zalán Borsos, Neil Zeghidour, Marco Tagliasacchi. 2023-03-23. LMCodec: A Low Bitrate Speech Codec With Causal Transformer Models. https://arxiv.org/abs/2303.12984

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