OnlineTTS

OnlineTTS is an application that allows you to use online text-to-speech services (such as WaveNet currently) as a regular TTS engine.

*********IMPORTANT WARNING**********
The possibility of OnlineTTS work is entirely dependent on Google's online text-to-speech services and the availability and quality of the Internet connection.
Google Cloud TTS (WaveNet) is a paid service. They will charge you a usage fee (excluding free monthly quota). I am not responsible for any Google service charges. You are solely responsible for avoiding excessive charges and for protecting your passwords and API key from abuse. My app (OnlineTTS) sends any data exclusively to Google TTS services and nowhere else. I highly recommend installing the app only from Google Play and disabling the API key in Google Cloud if you are not going to use it for a long time.
OnlineTTS is not recommended for use with critical accessibility applications, such as TalkBack.
OnlineTTS does not support output to an audio file.
All this you should consider when deciding whether to purchase this application.
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Encoding: OGG_OPUS, MP3.
Supported languages: Chinese (China), Chinese (Taiwan), English (Australia), English (India), English (United Kingdom), English (United States), French (Canadian), French (France), German (Germany), Hindi (India), Indonesian (Indonesia), Italian (Italy), Japanese (Japan), Korean (Korea), Portuguese (Portugal), Russian (Russia), Spanish (Spain), Spanish (United States), Turkish (Turkey), Vietnamese (Vietnam).
Most helpful resource on getting an API key and managing WaveNet usage: https://hyperionics.com/atVoice/WaveNet.html
Better to register on Google Cloud and get an API key in advance.

The stability of OnlineTTS depends both on Google services and on the quality of communication with them via the Internet, as well as on the Android firmware and settings for saving traffic and battery (especially when working with the screen off). The size of the text sent by readers also affects (the smaller the better). There is nothing I can do about these failure reasons. Each failure leads to the loss of a part of the text. If the number of crashes and therefore the quality of OnlineTTS is unacceptable, you have 48 hours since you bought an app to request a refund through Google Play.