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Overview

TelnyxFrameSerializer enables integration with Telnyx’s WebSocket media streaming protocol, allowing your Pipecat application to handle phone calls via Telnyx’s voice services.

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Features

  • Bidirectional audio conversion between Pipecat and Telnyx
  • DTMF (touch-tone) event handling
  • Automatic call termination via Telnyx’s REST API
  • Support for multiple audio encodings (PCMU, PCMA)

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Installation

The TelnyxFrameSerializer does not require any additional dependencies beyond the core Pipecat library.

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Configuration

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Constructor Parameters

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stream_id
str
required
The Stream ID for Telnyx
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outbound_encoding
str
required
The encoding type for outbound audio (e.g., “PCMU”, “PCMA”)
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inbound_encoding
str
required
The encoding type for inbound audio (e.g., “PCMU”, “PCMA”)
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call_control_id
Optional[str]
default:"None"
The Call Control ID for the Telnyx call (required for auto hang-up)
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api_key
Optional[str]
default:"None"
Your Telnyx API key (required for auto hang-up)
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params
InputParams
default:"InputParams()"
Configuration parameters

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InputParams Configuration

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telnyx_sample_rate
int
default:"8000"
Sample rate used by Telnyx (typically 8kHz)
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sample_rate
int | None
default:"None"
Optional override for pipeline input sample rate
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inbound_encoding
str
default:"PCMU"
Audio encoding for data sent to Telnyx
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outbound_encoding
str
default:"PCMU"
Audio encoding for data received from Telnyx
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auto_hang_up
bool
default:"True"
Whether to automatically terminate call on EndFrame

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Basic Usage

from pipecat.serializers.telnyx import TelnyxFrameSerializer
from pipecat.transports.network.fastapi_websocket import (
    FastAPIWebsocketTransport,
    FastAPIWebsocketParams
)

# Extract required values from Telnyx WebSocket connection
stream_id = call_data["stream_id"]
call_control_id = call_data["start"]["call_control_id"]
outbound_encoding = call_data["start"]["media_format"]["encoding"]

# Create serializer
serializer = TelnyxFrameSerializer(
    stream_id=stream_id,
    outbound_encoding=outbound_encoding,
    inbound_encoding="PCMU",
    call_control_id=call_control_id,
    api_key=os.getenv("TELNYX_API_KEY")
)

# Use with FastAPIWebsocketTransport
transport = FastAPIWebsocketTransport(
    websocket=websocket,
    params=FastAPIWebsocketParams(
        audio_in_enabled=True,
        audio_out_enabled=True,
        vad_analyzer=SileroVADAnalyzer(),
        serializer=serializer,
    )
)

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Hang-up Functionality

When auto_hang_up is enabled, the serializer will automatically hang up the Telnyx call when an EndFrame or CancelFrame is processed, using Telnyx’s REST API: 
# Properly configured with hang-up support
serializer = TelnyxFrameSerializer(
    stream_id=stream_id,
    outbound_encoding=outbound_encoding,
    inbound_encoding="PCMU",
    call_control_id=call_control_id,    # Required for auto hang-up
    api_key=os.getenv("TELNYX_API_KEY") # Required for auto hang-up
)

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Server Code Example

Here’s a complete example of handling a Telnyx WebSocket connection: 
from fastapi import FastAPI, WebSocket
from pipecat.serializers.telnyx import TelnyxFrameSerializer
import json
import os

app = FastAPI()

@app.websocket("/ws")
async def websocket_endpoint(websocket: WebSocket):
    await websocket.accept()

    # Read initial messages from Telnyx
    start_data = websocket.iter_text()
    await start_data.__anext__()  # Skip first message

    # Parse the second message to get call details
    call_data = json.loads(await start_data.__anext__())

    # Extract Telnyx-specific IDs and encoding
    stream_id = call_data["stream_id"]
    call_control_id = call_data["start"]["call_control_id"]
    outbound_encoding = call_data["start"]["media_format"]["encoding"]

    # Create serializer with API key for auto hang-up
    serializer = TelnyxFrameSerializer(
        stream_id=stream_id,
        outbound_encoding=outbound_encoding,
        inbound_encoding="PCMU",
        call_control_id=call_control_id,
        api_key=os.getenv("TELNYX_API_KEY"),
    )

    # Continue with transport and pipeline setup...
See the Telnyx Chatbot example for a complete implementation.