LPCNet is a WIP [vocal-synthesis] system from Mozilla. From their Github README, "Work in progress software for researching low CPU complexity algorithms for speech synthesis and compression by applying Linear Prediction techniques to [WaveRNN]". "This software is an open source starting point for LPCNet/WaveRNN-based speech synthesis and coding."
Github repo: https://github.com/mozilla/LPCNet
Terrific writeup that explains the justification for LPCNet, [WaveRNN], and how it compares to [wavenet]: https://jmvalin.ca/demo/lpcnet/
Archive link for above: https://web.archive.org/web/20210719065916/https://jmvalin.ca/demo/lpcnet/
The lead contributor seems to be [jmvalin]. It shares some code with [opus], and he has a research paper detailing how he integrated it with Opus itself to provide efficient low-bitrate transmission of speech: https://jmvalin.ca/papers/opusnet.pdf