"""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"" self._last_vad_status: str = "Silence" # 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: # 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 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 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 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