Add VonageFrameSerializer for Vonage Voice API

changelog/3265.added.md

@@ -0,0 +1 @@
+- Added `VonageFrameSerializer` in support of Vonage's Voice API over websockets.

src/pipecat/serializers/vonage.py

@@ -0,0 +1,194 @@
+#
+# Copyright (c) 2024–2025, Daily
+#
+# SPDX-License-Identifier: BSD 2-Clause License
+#
+
+"""Vonage Voice API WebSocket serializer for Pipecat."""
+
+import json
+from typing import Optional
+
+from loguru import logger
+from pydantic import BaseModel
+
+from pipecat.audio.dtmf.types import KeypadEntry
+from pipecat.audio.utils import create_stream_resampler
+from pipecat.frames.frames import (
+    AudioRawFrame,
+    Frame,
+    InputAudioRawFrame,
+    InputDTMFFrame,
+    InterruptionFrame,
+    OutputTransportMessageFrame,
+    OutputTransportMessageUrgentFrame,
+    StartFrame,
+)
+from pipecat.serializers.base_serializer import FrameSerializer, FrameSerializerType
+
+
+class VonageFrameSerializer(FrameSerializer):
+    """Serializer for Vonage Voice API WebSocket protocol.
+
+    This serializer handles converting between Pipecat frames and Vonage's WebSocket
+    voice streaming protocol. It supports audio conversion (16-bit linear PCM),
+    control commands like clear and notify, and DTMF input handling.
+
+    The Vonage Voice API uses:
+    - Binary messages for audio data (16-bit linear PCM)
+    - Text messages (JSON) for control commands, events, and DTMF
+
+    Note: Ref docs for WebSocket API:
+        https://developer.vonage.com/en/voice/voice-api/guides/websockets
+    """
+
+    class InputParams(BaseModel):
+        """Configuration parameters for VonageFrameSerializer.
+
+        Parameters:
+            vonage_sample_rate: Sample rate used by Vonage, defaults to 16000 Hz.
+                Common values: 8000, 16000, 24000 Hz.
+            sample_rate: Optional override for pipeline input sample rate.
+        """
+
+        vonage_sample_rate: int = 16000
+        sample_rate: Optional[int] = None
+
+    def __init__(self, params: Optional[InputParams] = None):
+        """Initialize the VonageFrameSerializer.
+
+        Args:
+            params: Configuration parameters.
+        """
+        self._params = params or VonageFrameSerializer.InputParams()
+
+        self._vonage_sample_rate = self._params.vonage_sample_rate
+        self._sample_rate = 0  # Pipeline input rate
+
+        self._input_resampler = create_stream_resampler()
+        self._output_resampler = create_stream_resampler()
+
+    @property
+    def type(self) -> FrameSerializerType:
+        """Gets the serializer type.
+
+        Returns:
+            The serializer type (MIXED for Vonage - supports both binary and text).
+        """
+        return FrameSerializerType.MIXED
+
+    async def setup(self, frame: StartFrame):
+        """Sets up the serializer with pipeline configuration.
+
+        Args:
+            frame: The StartFrame containing pipeline configuration.
+        """
+        self._sample_rate = self._params.sample_rate or frame.audio_in_sample_rate
+
+    async def serialize(self, frame: Frame) -> str | bytes | None:
+        """Serializes a Pipecat frame to Vonage WebSocket format.
+
+        Handles conversion of various frame types to Vonage WebSocket messages.
+
+        Args:
+            frame: The Pipecat frame to serialize.
+
+        Returns:
+            Serialized data as string (JSON commands) or bytes (audio), or None if the frame isn't handled.
+        """
+        if isinstance(frame, InterruptionFrame):
+            # Clear the audio buffer to stop playback immediately
+            answer = {"action": "clear"}
+            return json.dumps(answer)
+        elif isinstance(frame, AudioRawFrame):
+            data = frame.audio
+
+            # Output: Convert PCM at frame's rate to Vonage's sample rate (16-bit linear PCM)
+            serialized_data = await self._output_resampler.resample(
+                data, frame.sample_rate, self._vonage_sample_rate
+            )
+            if serialized_data is None or len(serialized_data) == 0:
+                # Ignoring in case we don't have audio
+                return None
+
+            # Vonage expects raw binary PCM data (not base64 encoded)
+            return serialized_data
+        elif isinstance(frame, (OutputTransportMessageFrame, OutputTransportMessageUrgentFrame)):
+            # Allow sending custom JSON commands (e.g., notify)
+            return json.dumps(frame.message)
+
+        return None
+
+    async def deserialize(self, data: str | bytes) -> Frame | None:
+        """Deserializes Vonage WebSocket data to Pipecat frames.
+
+        Handles conversion of Vonage events to appropriate Pipecat frames.
+        - Binary messages contain audio data (16-bit linear PCM)
+        - Text messages contain JSON events (websocket:connected, websocket:cleared, dtmf, etc.)
+
+        Args:
+            data: The raw WebSocket data from Vonage.
+
+        Returns:
+            A Pipecat frame corresponding to the Vonage event, or None if unhandled.
+        """
+        # Check if this is binary audio data
+        if isinstance(data, bytes):
+            # Binary message = audio data (16-bit linear PCM)
+            payload = data
+
+            # Input: Convert Vonage's PCM audio to pipeline sample rate
+            deserialized_data = await self._input_resampler.resample(
+                payload,
+                self._vonage_sample_rate,
+                self._sample_rate,
+            )
+            if deserialized_data is None or len(deserialized_data) == 0:
+                # Ignoring in case we don't have audio
+                return None
+
+            audio_frame = InputAudioRawFrame(
+                audio=deserialized_data,
+                num_channels=1,  # Vonage uses mono audio
+                sample_rate=self._sample_rate,  # Use the configured pipeline input rate
+            )
+            return audio_frame
+        else:
+            # Text message = JSON event
+            try:
+                message = json.loads(data)
+                event = message.get("event")
+
+                # Handle different event types
+                if event == "websocket:connected":
+                    logger.debug(
+                        f"Vonage WebSocket connected: content-type={message.get('content-type')}"
+                    )
+                    return None
+                elif event == "websocket:cleared":
+                    logger.debug("Vonage audio buffer cleared")
+                    return None
+                elif event == "websocket:notify":
+                    logger.debug(f"Vonage notify event: {message.get('payload')}")
+                    return None
+                elif event == "websocket:dtmf":
+                    # Handle DTMF input
+                    # Vonage may send digit in different formats, try both
+                    digit = message.get("digit") or message.get("dtmf", {}).get("digit")
+                    if digit:
+                        logger.debug(f"Received DTMF digit: {digit}")
+                        try:
+                            return InputDTMFFrame(KeypadEntry(digit))
+                        except ValueError:
+                            logger.warning(f"Invalid DTMF digit received: {digit}")
+                            return None
+                    else:
+                        logger.warning(f"DTMF event received but no digit found: {message}")
+                    return None
+                else:
+                    logger.debug(f"Vonage event: {event}")
+                    return None
+
+            except json.JSONDecodeError:
+                logger.warning(f"Failed to parse JSON message from Vonage: {data}")
+                return None