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Callbacks

TTS Wrapper provides a simple callback system to handle speech events. There are three main callbacks available:

  • onStart: Triggered when speech playback begins
  • onEnd: Triggered when speech playback ends
  • started-word: Triggered when a word starts being spoken

Using Callbacks​

You can connect callback functions to these events using the connect() method:

from tts_wrapper import PollyClient, PollyTTS

# Initialize TTS
client = PollyClient(credentials=('region', 'key_id', 'access_key'))
tts = PollyTTS(client)

# Define callback functions
def on_start():
    print("Speech started")

def on_end():
    print("Speech ended")

def on_word(word: str):
    print(f"Speaking word: {word}")

# Connect callbacks
tts.connect("onStart", on_start)
tts.connect("onEnd", on_end)
tts.connect("started-word", on_word)

# Speak text with callbacks
tts.speak("Hello, this is a test of the callback system.")

Callback Timing​

  • The onStart callback is triggered when audio playback actually begins
  • The onEnd callback is triggered when the entire text has been spoken
  • The started-word callback is triggered at the start of each word

Example: Progress Tracking​

Here's an example of using callbacks to track speech progress:

def on_start():
    print("Starting speech...")

def on_end():
    print("Speech complete!")

def on_word(word: str):
    print(f"Currently speaking: {word}")

# Connect all callbacks
tts.connect("onStart", on_start)
tts.connect("onEnd", on_end)
tts.connect("started-word", on_word)

# Speak with progress tracking
text = "This is a test of progress tracking."
tts.speak(text)

Best Practices​

  1. Keep Callbacks Light: Callback functions should be quick and not block execution
  2. Handle Exceptions: Always include error handling in your callbacks
  3. Cleanup: Clear callbacks when no longer needed by setting them to None
  4. Thread Safety: Remember that callbacks may be called from different threads

Next Steps​