Using Phonemes in TTS with Meta Voice SDK: Wit.ai, Custom Models, or ONNX in Unity?

Hi all,

I'm working on a Unity project where speech technology is central, and I'm facing a hurdle with Meta's Voice SDK. My primary need is to use phonemes directly for text-to-speech (TTS), but I've found that Wit.ai does not support direct IPA (International Phonetic Alphabet) input or return phoneme-level control for TTS.

Questions & Discussion Points:

• Is there any way to use Wit.ai for phoneme or IPA-based TTS, or is this currently unsupported?
• Are there recommended approaches to integrate speech models based on self-supervised learning (like wav2vec 2.0, HuBERT, or WavLM) with Unity, either alongside or instead of Wit.ai?
• For complete control over TTS—especially for phoneme-level synthesis—would it make sense to bypass Wit.ai entirely and run a model (converted to ONNX) for inference directly inside Unity?
• Have others run into similar limitations, and if so, what workflows or toolchains have worked best for you?

I’d appreciate any advice/examples for integrating more advanced or flexible TTS pipelines into Unity, especially those compatible with IPA/phoneme input or utilizing state-of-the-art self-supervised models.

Thanks!