For my native language, Norwegian, Piper TTS is at best "usable", and sometimes a fair bit worse than that. At least in its default form[1].
Especially the rhythm and timing is often very jarring making words difficult to understand, especially when the pitch is not quite right.
It also doesn't seem to know about pacing, ignoring semicolon and comma.
Combined I often need to think hard about what it just said, or even listen to it again.
I also notice these issues in the various English voice models to varying degrees, so seems to be an inherent problem. Or can it be improved significantly with training it yourself?
I saw that the piper-phonemize project linked to espeak-ng, and so I tried to pass the Piper sample text through espeak-ng and the way it phonemicized the text had the same rhythm issues that I noted in the TTS sample. Ie it put the stresses in the same wrong places in certain words and such.
This was also reflected in the voice output of espeak-ng, even though it's overall quality was vastly subpar compared to Piper TTS (as expected).
So it seems that improving this aspect might be one way to get better performance out of Piper for my language. Not sure how easy that'll be tho...
Especially the rhythm and timing is often very jarring making words difficult to understand, especially when the pitch is not quite right.
It also doesn't seem to know about pacing, ignoring semicolon and comma.
Combined I often need to think hard about what it just said, or even listen to it again.
I also notice these issues in the various English voice models to varying degrees, so seems to be an inherent problem. Or can it be improved significantly with training it yourself?
[1]: https://rhasspy.github.io/piper-samples/