relation between piper and espeak

[siddjain]

I noticed that piper depends on espeak which itself is a full-fledged TTS engine if I am not mistaken. So what value-add does piper provide on top of espeak? Is piper simply a wrapper? can someone help me understand?

PS: Also if espeak uses GPL License how can Piper use MIT License?

[synesthesiam]

Previous discussion here: #93

In short:

• espeak is used to get phonemes only. Piper uses a neural network model vs. espeak's basic wave synthesis. Listen to espeak vs. piper and you will hear what it adds 😄
• espeak is technically optional, and will be replaced entirely in the next version of piper to avoid any possible licensing issues