TTS Tags

This page provides an overview on the available tags to add into texts sent to Navels text-to-speech, e.g.

robot.say("<lang,de1>Hallo<lang,en1>Hello.<alt,1>Hello.")

Overview of tags

Example	Explanation
<alt,1>	Choose alternative pronounciation for the following word. Number enumerates options.
<lang,se1>	Permanently change voice to different language. See below.
<mrk,20>	Add bookmark to trigger an event via callback. See below.
<pau,25>	Pause speech for 25ms
<prn,h @ l @ U>	Give phonetic string
<rpit,120>	Permanently alter the voice pitch. The number is a percentage of the default pitch.
<rspd,120>	Permanently set speed in percent
<spell,broccoli>	Say letters of given word one by one
<vol,120>	Permanently set speech volume (20 to 400). Note that you can also set the system volume.
<word,I am fine>	Say given words one by one

Switch language

If your robot supports multiple languages, you can switch between them by inserting a tag into the text:

robot.say("<lang,de1>Hallo<lang,en1>Hello")

Setting a language is permanent until reboot. It resets most other permanent settings. Availablilty of languages depends on your purchase. Navel by default comes with one language installed. Valid language tags are

• de1: German

• en1: English

• es1: Spanish

• it1: Italian

• nl1: Dutch

• pt1: Portuguese

• sw1: Swedish

Bookmarks

This will allow you to register custom callbacks to be called at specific points during speech.

Registering callbacks

The set_bookmark_callback() function can be used to easily register new callbacks by providing a number and an async function that takes a single Robot as its only input:

import asyncio

import navel

async def close_eyes(robot: navel.Robot):
    print("Closing eyes")
    robot.head_eyelids(0, 0)

async def open_eyes(robot: navel.Robot):
    print("Opening eyes")
    robot.head_eyelids(1, 1)

async def main():
    async with navel.Robot() as robot:
        robot.set_bookmark_callback(0, close_eyes)
        robot.set_bookmark_callback(1, open_eyes)


if __name__ == "__main__":
    asyncio.run(main())

Warning

The callback system only supports numbers between 0 and 65535. Additionally, we plan to implement some built-in default callbacks using the highest numbers in the range, so we suggest to avoid going over 60000 if possible.

Note

Only one callback can be registered per bookmark number. Any subsequent calls to set_bookmark_callback with the same number will replace whatever the previous callback was.

If you run the code, you may notice nothing happens yet. That’s to be expected, since we only registered the callbacks without actually calling them anywhere.

Executing callbacks

Callbacks will be automatically executed when the text-to-speech engine reaches the place in the string where they are placed.

You can add them directly into the text you want the robot to say by using the format "<mrk,#>". To see this in action, try adding the following directly after line 16 from above:

robot.say("Look, I can <mrk,0>close my eyes, and <mrk,1>open them!")

Using callbacks like this allows you to easily synchronize speech and movement.