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Overview

LmntTTSService provides text-to-speech capabilities using LMNT’s WebSocket-based streaming API. It supports real-time audio generation with multiple voices and languages.

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Installation

To use LmntTTSService, install the required dependencies:

pip install pipecat-ai[lmnt]

You’ll also need to set up your LMNT API key as an environment variable: LMNT_API_KEY

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Configuration

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Constructor Parameters

api_key
str
required

Your LMNT API key

voice_id
str
required

LMNT voice identifier

sample_rate
int
default: "24000"

Output audio sample rate in Hz

language
Language
default: "Language.EN"

Synthesis language

text_filter
BaseTextFilter
default: "None"

Modifies text provided to the TTS. Learn more about the available filters.

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Output Frames

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Control Frames

TTSStartedFrame
Frame

Signals start of speech synthesis

TTSStoppedFrame
Frame

Signals completion of speech synthesis

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Audio Frames

TTSAudioRawFrame
Frame

Contains generated audio data with: - PCM audio format (16-bit) - Specified sample rate - Single channel (mono)

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Error Frames

ErrorFrame
Frame

Contains LMNT API error information

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Methods

See the TTS base class methods for additional functionality.

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Language Support

Supports multiple languages and regional variants:

Language CodeDescriptionService Code
Language.DEGermande
Language.ENEnglish (US)en
Language.EN_AUEnglish (Australia)en
Language.EN_GBEnglish (UK)en
Language.EN_INEnglish (India)en
Language.EN_NZEnglish (New Zealand)en
Language.ESSpanishes
Language.FRFrenchfr
Language.FR_CAFrench (Canada)fr
Language.KOKoreanko
Language.PTPortuguesept
Language.PT_BRPortuguese (Brazil)pt
Language.ZHChinese (Simplified)zh
Language.ZH_TWChinese (Traditional)zh

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Usage Example

from pipecat.services.lmnt import LmntTTSService
from pipecat.transcriptions.language import Language

# Configure service
tts_service = LmntTTSService(
    api_key="your-lmnt-api-key",
    voice_id="your-voice-id",
    sample_rate=24000,
    language=Language.EN
)

# Use in pipeline
pipeline = Pipeline([
    text_input,         # Produces text
    tts_service,        # Converts text to speech
    audio_output        # Plays audio
])

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Frame Flow

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Metrics Support

The service collects processing metrics:

  • Time to First Byte (TTFB)
  • Processing duration
  • Character usage
  • WebSocket connection status

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Notes

  • Supports streaming synthesis
  • Handles WebSocket lifecycle
  • Provides real-time audio chunks
  • Manages connection state
  • Supports interruptions
  • Thread-safe processing
  • Automatic error handling
  • Includes metrics collection
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