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py-active-call/core/duplex_pipeline.py
2026-02-06 08:40:42 +08:00

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"""Full duplex audio pipeline for AI voice conversation.
This module implements the core duplex pipeline that orchestrates:
- VAD (Voice Activity Detection)
- EOU (End of Utterance) Detection
- ASR (Automatic Speech Recognition) - optional
- LLM (Language Model)
- TTS (Text-to-Speech)
Inspired by pipecat's frame-based architecture and active-call's
event-driven design.
"""
import asyncio
import time
from typing import Optional, Callable, Awaitable
from loguru import logger
from core.transports import BaseTransport
from core.conversation import ConversationManager, ConversationState
from core.events import get_event_bus
from processors.vad import VADProcessor, SileroVAD
from processors.eou import EouDetector
from services.base import BaseLLMService, BaseTTSService, BaseASRService
from services.llm import OpenAILLMService, MockLLMService
from services.tts import EdgeTTSService, MockTTSService
from services.asr import BufferedASRService
from services.siliconflow_tts import SiliconFlowTTSService
from services.siliconflow_asr import SiliconFlowASRService
from app.config import settings
class DuplexPipeline:
"""
Full duplex audio pipeline for AI voice conversation.
Handles bidirectional audio flow with:
- User speech detection and transcription
- AI response generation
- Text-to-speech synthesis
- Barge-in (interruption) support
Architecture (inspired by pipecat):
User Audio → VAD → EOU → [ASR] → LLM → TTS → Audio Out
Barge-in Detection → Interrupt
"""
def __init__(
self,
transport: BaseTransport,
session_id: str,
llm_service: Optional[BaseLLMService] = None,
tts_service: Optional[BaseTTSService] = None,
asr_service: Optional[BaseASRService] = None,
system_prompt: Optional[str] = None,
greeting: Optional[str] = None
):
"""
Initialize duplex pipeline.
Args:
transport: Transport for sending audio/events
session_id: Session identifier
llm_service: LLM service (defaults to OpenAI)
tts_service: TTS service (defaults to EdgeTTS)
asr_service: ASR service (optional)
system_prompt: System prompt for LLM
greeting: Optional greeting to speak on start
"""
self.transport = transport
self.session_id = session_id
self.event_bus = get_event_bus()
# Initialize VAD
self.vad_model = SileroVAD(
model_path=settings.vad_model_path,
sample_rate=settings.sample_rate
)
self.vad_processor = VADProcessor(
vad_model=self.vad_model,
threshold=settings.vad_threshold
)
# Initialize EOU detector
self.eou_detector = EouDetector(
silence_threshold_ms=settings.vad_eou_threshold_ms,
min_speech_duration_ms=settings.vad_min_speech_duration_ms
)
# Initialize services
self.llm_service = llm_service
self.tts_service = tts_service
self.asr_service = asr_service # Will be initialized in start()
# Track last sent transcript to avoid duplicates
self._last_sent_transcript = ""
# Conversation manager
self.conversation = ConversationManager(
system_prompt=system_prompt,
greeting=greeting
)
# State
self._running = True
self._is_bot_speaking = False
self._current_turn_task: Optional[asyncio.Task] = None
self._audio_buffer: bytes = b""
max_buffer_seconds = settings.max_audio_buffer_seconds if hasattr(settings, "max_audio_buffer_seconds") else 30
self._max_audio_buffer_bytes = int(settings.sample_rate * 2 * max_buffer_seconds)
self._last_vad_status: str = "Silence"
self._process_lock = asyncio.Lock()
# Interruption handling
self._interrupt_event = asyncio.Event()
# Latency tracking - TTFB (Time to First Byte)
self._turn_start_time: Optional[float] = None
self._first_audio_sent: bool = False
# Barge-in filtering - require minimum speech duration to interrupt
self._barge_in_speech_start_time: Optional[float] = None
self._barge_in_min_duration_ms: int = settings.barge_in_min_duration_ms if hasattr(settings, 'barge_in_min_duration_ms') else 50
self._barge_in_speech_frames: int = 0 # Count speech frames
self._barge_in_silence_frames: int = 0 # Count silence frames during potential barge-in
self._barge_in_silence_tolerance: int = 3 # Allow up to 3 silence frames (60ms at 20ms chunks)
logger.info(f"DuplexPipeline initialized for session {session_id}")
async def start(self) -> None:
"""Start the pipeline and connect services."""
try:
# Connect LLM service
if not self.llm_service:
if settings.openai_api_key:
self.llm_service = OpenAILLMService(
api_key=settings.openai_api_key,
base_url=settings.openai_api_url,
model=settings.llm_model
)
else:
logger.warning("No OpenAI API key - using mock LLM")
self.llm_service = MockLLMService()
await self.llm_service.connect()
# Connect TTS service
if not self.tts_service:
if settings.tts_provider == "siliconflow" and settings.siliconflow_api_key:
self.tts_service = SiliconFlowTTSService(
api_key=settings.siliconflow_api_key,
voice=settings.tts_voice,
model=settings.siliconflow_tts_model,
sample_rate=settings.sample_rate,
speed=settings.tts_speed
)
logger.info("Using SiliconFlow TTS service")
else:
self.tts_service = EdgeTTSService(
voice=settings.tts_voice,
sample_rate=settings.sample_rate
)
logger.info("Using Edge TTS service")
await self.tts_service.connect()
# Connect ASR service
if not self.asr_service:
if settings.asr_provider == "siliconflow" and settings.siliconflow_api_key:
self.asr_service = SiliconFlowASRService(
api_key=settings.siliconflow_api_key,
model=settings.siliconflow_asr_model,
sample_rate=settings.sample_rate,
interim_interval_ms=settings.asr_interim_interval_ms,
min_audio_for_interim_ms=settings.asr_min_audio_ms,
on_transcript=self._on_transcript_callback
)
logger.info("Using SiliconFlow ASR service")
else:
self.asr_service = BufferedASRService(
sample_rate=settings.sample_rate
)
logger.info("Using Buffered ASR service (no real transcription)")
await self.asr_service.connect()
logger.info("DuplexPipeline services connected")
# Speak greeting if configured
if self.conversation.greeting:
await self._speak(self.conversation.greeting)
except Exception as e:
logger.error(f"Failed to start pipeline: {e}")
raise
async def process_audio(self, pcm_bytes: bytes) -> None:
"""
Process incoming audio chunk.
This is the main entry point for audio from the user.
Args:
pcm_bytes: PCM audio data (16-bit, mono, 16kHz)
"""
if not self._running:
return
try:
async with self._process_lock:
# 1. Process through VAD
vad_result = self.vad_processor.process(pcm_bytes, settings.chunk_size_ms)
vad_status = "Silence"
if vad_result:
event_type, probability = vad_result
vad_status = "Speech" if event_type == "speaking" else "Silence"
# Emit VAD event
await self.event_bus.publish(event_type, {
"trackId": self.session_id,
"probability": probability
})
else:
# No state change - keep previous status
vad_status = self._last_vad_status
# Update state based on VAD
if vad_status == "Speech" and self._last_vad_status != "Speech":
await self._on_speech_start()
self._last_vad_status = vad_status
# 2. Check for barge-in (user speaking while bot speaking)
# Filter false interruptions by requiring minimum speech duration
if self._is_bot_speaking:
if vad_status == "Speech":
# User is speaking while bot is speaking
self._barge_in_silence_frames = 0 # Reset silence counter
if self._barge_in_speech_start_time is None:
# Start tracking speech duration
self._barge_in_speech_start_time = time.time()
self._barge_in_speech_frames = 1
logger.debug("Potential barge-in detected, tracking duration...")
else:
self._barge_in_speech_frames += 1
# Check if speech duration exceeds threshold
speech_duration_ms = (time.time() - self._barge_in_speech_start_time) * 1000
if speech_duration_ms >= self._barge_in_min_duration_ms:
logger.info(f"Barge-in confirmed after {speech_duration_ms:.0f}ms of speech ({self._barge_in_speech_frames} frames)")
await self._handle_barge_in()
else:
# Silence frame during potential barge-in
if self._barge_in_speech_start_time is not None:
self._barge_in_silence_frames += 1
# Allow brief silence gaps (VAD flickering)
if self._barge_in_silence_frames > self._barge_in_silence_tolerance:
# Too much silence - reset barge-in tracking
logger.debug(f"Barge-in cancelled after {self._barge_in_silence_frames} silence frames")
self._barge_in_speech_start_time = None
self._barge_in_speech_frames = 0
self._barge_in_silence_frames = 0
# 3. Buffer audio for ASR
if vad_status == "Speech" or self.conversation.state == ConversationState.LISTENING:
self._audio_buffer += pcm_bytes
if len(self._audio_buffer) > self._max_audio_buffer_bytes:
# Keep only the most recent audio to cap memory usage
self._audio_buffer = self._audio_buffer[-self._max_audio_buffer_bytes:]
await self.asr_service.send_audio(pcm_bytes)
# For SiliconFlow ASR, trigger interim transcription periodically
# The service handles timing internally via start_interim_transcription()
# 4. Check for End of Utterance - this triggers LLM response
if self.eou_detector.process(vad_status):
await self._on_end_of_utterance()
except Exception as e:
logger.error(f"Pipeline audio processing error: {e}", exc_info=True)
async def process_text(self, text: str) -> None:
"""
Process text input (chat command).
Allows direct text input to bypass ASR.
Args:
text: User text input
"""
if not self._running:
return
logger.info(f"Processing text input: {text[:50]}...")
# Cancel any current speaking
await self._stop_current_speech()
# Start new turn
await self.conversation.end_user_turn(text)
self._current_turn_task = asyncio.create_task(self._handle_turn(text))
async def interrupt(self) -> None:
"""Interrupt current bot speech (manual interrupt command)."""
await self._handle_barge_in()
async def _on_transcript_callback(self, text: str, is_final: bool) -> None:
"""
Callback for ASR transcription results.
Streams transcription to client for display.
Args:
text: Transcribed text
is_final: Whether this is the final transcription
"""
# Avoid sending duplicate transcripts
if text == self._last_sent_transcript and not is_final:
return
self._last_sent_transcript = text
# Send transcript event to client
await self.transport.send_event({
"event": "transcript",
"trackId": self.session_id,
"text": text,
"isFinal": is_final,
"timestamp": self._get_timestamp_ms()
})
logger.debug(f"Sent transcript ({'final' if is_final else 'interim'}): {text[:50]}...")
async def _on_speech_start(self) -> None:
"""Handle user starting to speak."""
if self.conversation.state == ConversationState.IDLE:
await self.conversation.start_user_turn()
self._audio_buffer = b""
self._last_sent_transcript = ""
self.eou_detector.reset()
# Clear ASR buffer and start interim transcriptions
if hasattr(self.asr_service, 'clear_buffer'):
self.asr_service.clear_buffer()
if hasattr(self.asr_service, 'start_interim_transcription'):
await self.asr_service.start_interim_transcription()
logger.debug("User speech started")
async def _on_end_of_utterance(self) -> None:
"""Handle end of user utterance."""
if self.conversation.state != ConversationState.LISTENING:
return
# Stop interim transcriptions
if hasattr(self.asr_service, 'stop_interim_transcription'):
await self.asr_service.stop_interim_transcription()
# Get final transcription from ASR service
user_text = ""
if hasattr(self.asr_service, 'get_final_transcription'):
# SiliconFlow ASR - get final transcription
user_text = await self.asr_service.get_final_transcription()
elif hasattr(self.asr_service, 'get_and_clear_text'):
# Buffered ASR - get accumulated text
user_text = self.asr_service.get_and_clear_text()
# Skip if no meaningful text
if not user_text or not user_text.strip():
logger.debug("EOU detected but no transcription - skipping")
# Reset for next utterance
self._audio_buffer = b""
self._last_sent_transcript = ""
# Return to idle; don't force LISTENING which causes buffering on silence
await self.conversation.set_state(ConversationState.IDLE)
return
logger.info(f"EOU detected - user said: {user_text[:100]}...")
# Send final transcription to client
await self.transport.send_event({
"event": "transcript",
"trackId": self.session_id,
"text": user_text,
"isFinal": True,
"timestamp": self._get_timestamp_ms()
})
# Clear buffers
self._audio_buffer = b""
self._last_sent_transcript = ""
# Process the turn - trigger LLM response
# Cancel any existing turn to avoid overlapping assistant responses
await self._stop_current_speech()
await self.conversation.end_user_turn(user_text)
self._current_turn_task = asyncio.create_task(self._handle_turn(user_text))
async def _handle_turn(self, user_text: str) -> None:
"""
Handle a complete conversation turn.
Uses sentence-by-sentence streaming TTS for lower latency.
Args:
user_text: User's transcribed text
"""
try:
# Start latency tracking
self._turn_start_time = time.time()
self._first_audio_sent = False
# Get AI response (streaming)
messages = self.conversation.get_messages()
full_response = ""
await self.conversation.start_assistant_turn()
self._is_bot_speaking = True
self._interrupt_event.clear()
# Sentence buffer for streaming TTS
sentence_buffer = ""
sentence_ends = {'', '', '', '', '\n'}
first_audio_sent = False
# Stream LLM response and TTS sentence by sentence
async for text_chunk in self.llm_service.generate_stream(messages):
if self._interrupt_event.is_set():
break
full_response += text_chunk
sentence_buffer += text_chunk
await self.conversation.update_assistant_text(text_chunk)
# Send LLM response streaming event to client
await self.transport.send_event({
"event": "llmResponse",
"trackId": self.session_id,
"text": text_chunk,
"isFinal": False,
"timestamp": self._get_timestamp_ms()
})
# Check for sentence completion - synthesize immediately for low latency
while any(end in sentence_buffer for end in sentence_ends):
# Find first sentence end
min_idx = len(sentence_buffer)
for end in sentence_ends:
idx = sentence_buffer.find(end)
if idx != -1 and idx < min_idx:
min_idx = idx
if min_idx < len(sentence_buffer):
sentence = sentence_buffer[:min_idx + 1].strip()
sentence_buffer = sentence_buffer[min_idx + 1:]
if sentence and not self._interrupt_event.is_set():
# Send track start on first audio
if not first_audio_sent:
await self.transport.send_event({
"event": "trackStart",
"trackId": self.session_id,
"timestamp": self._get_timestamp_ms()
})
first_audio_sent = True
# Synthesize and send this sentence immediately
await self._speak_sentence(sentence)
else:
break
# Send final LLM response event
if full_response and not self._interrupt_event.is_set():
await self.transport.send_event({
"event": "llmResponse",
"trackId": self.session_id,
"text": full_response,
"isFinal": True,
"timestamp": self._get_timestamp_ms()
})
# Speak any remaining text
if sentence_buffer.strip() and not self._interrupt_event.is_set():
if not first_audio_sent:
await self.transport.send_event({
"event": "trackStart",
"trackId": self.session_id,
"timestamp": self._get_timestamp_ms()
})
first_audio_sent = True
await self._speak_sentence(sentence_buffer.strip())
# Send track end
if first_audio_sent:
await self.transport.send_event({
"event": "trackEnd",
"trackId": self.session_id,
"timestamp": self._get_timestamp_ms()
})
# End assistant turn
await self.conversation.end_assistant_turn(
was_interrupted=self._interrupt_event.is_set()
)
except asyncio.CancelledError:
logger.info("Turn handling cancelled")
await self.conversation.end_assistant_turn(was_interrupted=True)
except Exception as e:
logger.error(f"Turn handling error: {e}", exc_info=True)
await self.conversation.end_assistant_turn(was_interrupted=True)
finally:
self._is_bot_speaking = False
# Reset barge-in tracking when bot finishes speaking
self._barge_in_speech_start_time = None
self._barge_in_speech_frames = 0
self._barge_in_silence_frames = 0
async def _speak_sentence(self, text: str) -> None:
"""
Synthesize and send a single sentence.
Args:
text: Sentence to speak
"""
if not text.strip() or self._interrupt_event.is_set():
return
try:
async for chunk in self.tts_service.synthesize_stream(text):
# Check interrupt at the start of each iteration
if self._interrupt_event.is_set():
logger.debug("TTS sentence interrupted")
break
# Track and log first audio packet latency (TTFB)
if not self._first_audio_sent and self._turn_start_time:
ttfb_ms = (time.time() - self._turn_start_time) * 1000
self._first_audio_sent = True
logger.info(f"[TTFB] Server first audio packet latency: {ttfb_ms:.0f}ms (session {self.session_id})")
# Send TTFB event to client
await self.transport.send_event({
"event": "ttfb",
"trackId": self.session_id,
"timestamp": self._get_timestamp_ms(),
"latencyMs": round(ttfb_ms)
})
# Double-check interrupt right before sending audio
if self._interrupt_event.is_set():
break
await self.transport.send_audio(chunk.audio)
await asyncio.sleep(0.005) # Small delay to prevent flooding
except asyncio.CancelledError:
logger.debug("TTS sentence cancelled")
except Exception as e:
logger.error(f"TTS sentence error: {e}")
async def _speak(self, text: str) -> None:
"""
Synthesize and send speech.
Args:
text: Text to speak
"""
if not text.strip():
return
try:
# Start latency tracking for greeting
speak_start_time = time.time()
first_audio_sent = False
# Send track start event
await self.transport.send_event({
"event": "trackStart",
"trackId": self.session_id,
"timestamp": self._get_timestamp_ms()
})
self._is_bot_speaking = True
# Stream TTS audio
async for chunk in self.tts_service.synthesize_stream(text):
if self._interrupt_event.is_set():
logger.info("TTS interrupted by barge-in")
break
# Track and log first audio packet latency (TTFB)
if not first_audio_sent:
ttfb_ms = (time.time() - speak_start_time) * 1000
first_audio_sent = True
logger.info(f"[TTFB] Greeting first audio packet latency: {ttfb_ms:.0f}ms (session {self.session_id})")
# Send TTFB event to client
await self.transport.send_event({
"event": "ttfb",
"trackId": self.session_id,
"timestamp": self._get_timestamp_ms(),
"latencyMs": round(ttfb_ms)
})
# Send audio to client
await self.transport.send_audio(chunk.audio)
# Small delay to prevent flooding
await asyncio.sleep(0.01)
# Send track end event
await self.transport.send_event({
"event": "trackEnd",
"trackId": self.session_id,
"timestamp": self._get_timestamp_ms()
})
except asyncio.CancelledError:
logger.info("TTS cancelled")
raise
except Exception as e:
logger.error(f"TTS error: {e}")
finally:
self._is_bot_speaking = False
async def _handle_barge_in(self) -> None:
"""Handle user barge-in (interruption)."""
if not self._is_bot_speaking:
return
logger.info("Barge-in detected - interrupting bot speech")
# Reset barge-in tracking
self._barge_in_speech_start_time = None
self._barge_in_speech_frames = 0
self._barge_in_silence_frames = 0
# IMPORTANT: Signal interruption FIRST to stop audio sending
self._interrupt_event.set()
self._is_bot_speaking = False
# Send interrupt event to client IMMEDIATELY
# This must happen BEFORE canceling services, so client knows to discard in-flight audio
await self.transport.send_event({
"event": "interrupt",
"trackId": self.session_id,
"timestamp": self._get_timestamp_ms()
})
# Cancel TTS
if self.tts_service:
await self.tts_service.cancel()
# Cancel LLM
if self.llm_service and hasattr(self.llm_service, 'cancel'):
self.llm_service.cancel()
# Interrupt conversation only if there is no active turn task.
# When a turn task exists, it will handle end_assistant_turn() to avoid double callbacks.
if not (self._current_turn_task and not self._current_turn_task.done()):
await self.conversation.interrupt()
# Reset for new user turn
await self.conversation.start_user_turn()
self._audio_buffer = b""
self.eou_detector.reset()
async def _stop_current_speech(self) -> None:
"""Stop any current speech task."""
if self._current_turn_task and not self._current_turn_task.done():
self._interrupt_event.set()
self._current_turn_task.cancel()
try:
await self._current_turn_task
except asyncio.CancelledError:
pass
# Ensure underlying services are cancelled to avoid leaking work/audio
if self.tts_service:
await self.tts_service.cancel()
if self.llm_service and hasattr(self.llm_service, 'cancel'):
self.llm_service.cancel()
self._is_bot_speaking = False
self._interrupt_event.clear()
async def cleanup(self) -> None:
"""Cleanup pipeline resources."""
logger.info(f"Cleaning up DuplexPipeline for session {self.session_id}")
self._running = False
await self._stop_current_speech()
# Disconnect services
if self.llm_service:
await self.llm_service.disconnect()
if self.tts_service:
await self.tts_service.disconnect()
if self.asr_service:
await self.asr_service.disconnect()
def _get_timestamp_ms(self) -> int:
"""Get current timestamp in milliseconds."""
import time
return int(time.time() * 1000)
@property
def is_speaking(self) -> bool:
"""Check if bot is currently speaking."""
return self._is_bot_speaking
@property
def state(self) -> ConversationState:
"""Get current conversation state."""
return self.conversation.state