Voice-to-Voice Pipeline
Interactive diagram of the complete voice pipeline for DigiDouble Phase 1 MVP. Select components for each block to visualize cumulative latency and estimated cost. Compare the Cascade approach (ASR → LLM → TTS) with end-to-end Voice-to-Voice.
Estimated Latency & Cost
DigiDouble Phase 1 target: <2s end-to-end (voice pipeline only, excluding avatar generation). Avatar generation adds 80–300ms (BeyondPresence) or 3–8s (HeyGen).
Converts audio stream to text. Streaming ASR sends partial transcripts to reduce LLM Time-to-First-Token. Critical latency block.
Industry reference for real-time ASR. Supports 30+ languages. Used by most voice agent frameworks.
Best sovereign option. Use faster-whisper with streaming VAD for near-real-time. Quantized small.en: ~200ms on CPU.
Good alternative with EU data residency option. Better for multi-speaker scenarios.
Key advantage: when combined with Inworld TTS and LLM Router, eliminates inter-component network hops. Semantic VAD reduces hallucination triggers. Use for Inworld Single-Provider stack.
ASR → LLM → TTS — modular, controllable, production-ready
Recommended for MVP Phase 1. Best stack: Deepgram Nova-3 + GPT-4o streaming + Cartesia Sonic 3. Sovereign alternative: Whisper.cpp + Llama 3.1 8B + Kokoro 82M.
Direct audio-in → audio-out — lowest latency, natural prosody
Recommended for R&D Axis 1 exploration (H2 2026). Not suitable for Phase 1 MVP due to lack of voice cloning. Monitor Voxtral TTS (Mistral) and Ultravox v0.5.
Recommended Stacks
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MVP Cloud Stack
Fastest path to working prototype
Optimal for Phase 1 MVP validation. Deepgram (75ms) + GPT-4o streaming (350ms) + Cartesia (40ms) + WebRTC (30ms) = ~505ms best-case. Voice cloning via Cartesia. No sovereignty — acceptable for prototype.
Sovereign Stack
Full Swiss sovereignty — Exoscale/OVH deployment
Full sovereignty for Swiss/EU institutional partners. Whisper.cpp (200ms) + Llama 3.1 8B (150ms) + Chatterbox (150ms) + Mem0 (20ms) + WebRTC (30ms) = ~710ms best-case. Voice cloning via Chatterbox. Deployable on Exoscale Geneva.
Inworld Single-Provider Stack
One provider: STT + LLM Router + TTS — no inter-component latency
Key advantage: Inworld STT + LLM Router + TTS share the same internal infrastructure — no inter-component network serialization. Estimated 30–50ms latency gain vs multi-provider cascade. WebRTC (10ms) + Inworld STT (80ms) + Mem0 (20ms) + GPT-4o streaming (350ms) + Inworld TTS Mini (120ms) + WebRTC (30ms) = ~490ms best-case. On-premise option enables Swiss sovereign deployment. Voice cloning + viseme timestamps included.
Hybrid Stack
Best quality/sovereignty balance for production
EU-sovereign LLM (Mistral) + sovereign TTS (Kokoro) + best ASR (Deepgram) + Mem0 long-term memory. Deepgram (75ms) + Mistral Nemo (200ms) + Kokoro (60ms) + Mem0 (20ms) + WebRTC (30ms) = ~555ms best-case. No voice cloning — add Chatterbox for persona.
Key decision: voice cloning
Voice cloning is critical for DigiDouble persona. Options: Cartesia (cloud, 40ms), Chatterbox (local, 150ms, MIT), ElevenLabs (cloud, 75ms, $75/1M). Sovereign stack requires Chatterbox + Kokoro combination.
Compare all TTS solutions
14 TTS/V2V solutions with comparative scores on 7 axes.
TTS State of the Art →