Add comprehensive TTS model documentation and research
Added detailed documentation for 10 TTS models: - Coqui TTS (XTTS-v2): High-quality multilingual with voice cloning - Mozilla TTS: Historical context, superseded by Coqui - Piper TTS: Fast, lightweight, 100+ voices - Chatterbox: Emotion control, 23 languages - Mimic 3: Privacy-focused, offline capable - eSpeak NG: 100+ languages, accessibility-focused - Kokoro TTS: Fast decoder-only architecture - Tortoise TTS: Studio-quality but slow - Step-Audio-EditX: Experimental LLM-based audio editing - Maya1: Indic languages specialist Created comprehensive research overview: - Complete model comparison matrix - Performance characteristics and feature analysis - License compatibility analysis - Integration roadmap and priorities - Raccoon Mission risk assessment Updated MODELS.md: - Added documentation index with links to all model docs - Added research overview reference - Added detailed doc references in existing sections - Added "Additional Models Under Research" section All documentation follows Raccoon Mission theme of rescuing abandoned open-source TTS models for long-term preservation.
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# TTS Models Research Overview
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**Last Updated:** 2025-11-09
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**Raccoon Mission Status:** 🦝 Active Rescue Operations
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## Executive Summary
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This document provides a comprehensive overview of open-source Text-to-Speech (TTS) models researched for integration into UncloseAI Speech. Our "Raccoon Mission" aims to rescue abandoned and at-risk TTS projects, ensuring their long-term preservation and availability.
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## Model Inventory
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### Currently Integrated ✅
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| Model | Status | Quality | Speed | Use Case |
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|-------|--------|---------|-------|----------|
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| [Piper TTS](../models/piper-tts.md) | Production | Good | Fast (0.05x RTF) | tts-1 (fast responses) |
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| [Coqui XTTS-v2](../models/coqui-tts.md) | Production | Excellent | Medium (0.3x RTF) | tts-1-hd (high quality) |
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### High Priority Candidates 🎯
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| Model | Priority | Key Strengths | Integration Effort |
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|-------|----------|---------------|-------------------|
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| [Chatterbox](../models/chatterbox.md) | High | Emotion control, 23 languages | Medium |
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| [Kokoro TTS](../models/kokoro-tts.md) | Medium | Fast, Apache-2.0 licensed | Medium |
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| Silero TTS | High | Active maintenance, small models | Low |
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| StyleTTS2 | High | Best quality/prosody | High |
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### Specialized Models 🔬
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| Model | Specialization | Integration Status |
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|-------|----------------|-------------------|
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| [Mimic 3](../models/mimic3.md) | Privacy-focused, offline | Candidate |
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| [eSpeak NG](../models/espeak-ng.md) | 100+ languages, accessibility | Niche |
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| [Maya1](../models/maya1.md) | Indic languages, diverse accents | Research |
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| [Step-Audio-EditX](../models/step-audio-editx.md) | Post-generation editing | Experimental |
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### Low Priority / Archived 📦
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| Model | Reason | Status |
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|-------|--------|--------|
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| [Mozilla TTS](../models/mozilla-tts.md) | Superseded by Coqui | Archived |
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| [Tortoise TTS](../models/tortoise-tts.md) | Too slow for production | Low priority |
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## Model Comparison Matrix
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### Performance Characteristics
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| Model | RTF | Quality (MOS) | Languages | License | Model Size |
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|-------|-----|---------------|-----------|---------|------------|
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| Piper TTS | 0.05x | 3.5-4.0 | 50+ | MIT | ~100MB |
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| Coqui XTTS-v2 | 0.3x | 4.2-4.5 | 20+ | Apache-2.0 | ~1.8GB |
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| Chatterbox | 0.2x | 4.0-4.3 | 23 | Apache-2.0 | ~1.2GB |
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| Kokoro TTS | 0.1-0.3x | 4.0-4.2 | Limited | Apache-2.0 | ~500MB |
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| Mimic 3 | 0.1x | 3.8-4.0 | Multiple | Apache-2.0 | 20-50MB |
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| eSpeak NG | <0.01x | 2.5-3.0 | 100+ | GPL-3.0 | <10MB |
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| Maya1 | Unknown | 4.0+ | 10+ Indic | MIT | ~1.5GB |
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| Tortoise TTS | 10-30x | 4.5-4.8 | English | Apache-2.0 | ~2GB |
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| Step-Audio-EditX | Variable | N/A | Multiple | Apache-2.0 | Unknown |
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| Mozilla TTS | 0.5x | 3.8-4.0 | Limited | MPL-2.0 | ~500MB |
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**RTF = Real-Time Factor** (lower is faster, 1.0 = real-time)
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**MOS = Mean Opinion Score** (1-5 scale, higher is better)
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### Feature Matrix
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| Model | Voice Cloning | Emotion Control | Multilingual | Offline | GPU Required |
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|-------|---------------|----------------|--------------|---------|--------------|
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| Piper TTS | ❌ | ❌ | ✅ | ✅ | ❌ |
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| Coqui XTTS-v2 | ✅ | ✅ | ✅ | ✅ | Recommended |
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| Chatterbox | ✅ | ✅ (unique) | ✅ | ✅ | Recommended |
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| Kokoro TTS | ✅ | ✅ | Limited | ✅ | Optional |
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| Mimic 3 | ❌ | Limited | ✅ | ✅ | ❌ |
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| eSpeak NG | ❌ | ❌ | ✅ | ✅ | ❌ |
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| Maya1 | ✅ | Unknown | ✅ | ✅ | Yes |
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| Tortoise TTS | ✅ | ✅ | Limited | ✅ | Yes |
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| Step-Audio-EditX | N/A | ✅ (editing) | ✅ | ✅ | Yes |
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| Mozilla TTS | Limited | ❌ | Limited | ✅ | Recommended |
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## Research Findings by Category
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### 1. Production-Ready Models
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#### Coqui XTTS-v2 (Currently Integrated)
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- **Status:** Company shut down 2024, community-maintained
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- **Quality:** Excellent (4.2-4.5 MOS)
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- **Key Feature:** Zero-shot voice cloning from 6-second samples
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- **Risk:** Upstream archived, needs mirroring
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- **Recommendation:** Continue use, establish mirrors
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- **Documentation:** [docs/models/coqui-tts.md](../models/coqui-tts.md)
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#### Piper TTS (Currently Integrated)
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- **Status:** Original project abandoned, OHF-Voice fork
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- **Quality:** Good (3.5-4.0 MOS)
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- **Key Feature:** Fastest inference, 100+ voices
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- **Risk:** Fork has no PyPI package
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- **Recommendation:** Vendor code or create PyPI package
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- **Documentation:** [docs/models/piper-tts.md](../models/piper-tts.md)
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#### Chatterbox (High Priority)
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- **Status:** Active development by Resemble AI
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- **Quality:** Very Good (4.0-4.3 MOS)
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- **Key Feature:** Unique emotion exaggeration control
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- **Risk:** Low - actively maintained
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- **Recommendation:** Integrate for emotion control features
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- **Documentation:** [docs/models/chatterbox.md](../models/chatterbox.md)
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### 2. Fast & Lightweight Models
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#### Kokoro TTS
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- **Architecture:** Decoder-only for speed
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- **Performance:** 0.1-0.3x RTF
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- **Best For:** Low-latency applications
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- **Limitation:** Fewer expressive options
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- **Documentation:** [docs/models/kokoro-tts.md](../models/kokoro-tts.md)
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#### Mimic 3
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- **Size:** 20-50MB per voice
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- **Performance:** 50-100ms latency
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- **Best For:** Privacy-focused, embedded systems
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- **Limitation:** Some robotic elements
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- **Documentation:** [docs/models/mimic3.md](../models/mimic3.md)
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#### eSpeak NG
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- **Technology:** Formant synthesis (not neural)
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- **Performance:** Extremely fast (<10ms)
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- **Best For:** Accessibility, 100+ languages
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- **Limitation:** Less natural than neural models
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- **Documentation:** [docs/models/espeak-ng.md](../models/espeak-ng.md)
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### 3. High-Quality Studio Models
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#### Tortoise TTS
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- **Technology:** Diffusion-based
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- **Quality:** Studio-grade (4.5-4.8 MOS)
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- **Performance:** 2-5 minutes per sentence
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- **Best For:** Offline content creation
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- **Not Suitable For:** Real-time API
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- **Documentation:** [docs/models/tortoise-tts.md](../models/tortoise-tts.md)
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### 4. Multilingual & Accent Diversity
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#### Maya1
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- **Origin:** India-based research
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- **Specialization:** Indic languages (Hindi, Tamil, etc.)
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- **Status:** Emerging, early documentation
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- **Best For:** Non-English markets
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- **Documentation:** [docs/models/maya1.md](../models/maya1.md)
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### 5. Experimental & Cutting Edge
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#### Step-Audio-EditX (November 2025)
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- **Innovation:** LLM-based audio editing
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- **Approach:** Post-generation refinement
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- **Status:** Very new, experimental
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- **Best For:** Creative audio workflows
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- **Documentation:** [docs/models/step-audio-editx.md](../models/step-audio-editx.md)
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### 6. Historical / Archived
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#### Mozilla TTS
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- **Status:** Archived, became Coqui TTS
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- **Historical Significance:** Pioneer in open-source TTS
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- **Current Recommendation:** Use Coqui instead
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- **Documentation:** [docs/models/mozilla-tts.md](../models/mozilla-tts.md)
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## License Compatibility Analysis
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### Commercial-Friendly Licenses ✅
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- **Apache-2.0:** Coqui XTTS-v2, Chatterbox, Kokoro, Mimic 3, Tortoise, Step-Audio-EditX
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- **MIT:** Piper TTS, Maya1
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- **MPL-2.0:** Mozilla TTS (permissive with copyleft for modifications)
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### Restricted Licenses ⚠️
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- **GPL-3.0:** eSpeak NG (copyleft, requires derivative works to be GPL)
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### Recommendation
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For commercial deployment, prioritize Apache-2.0 and MIT licensed models. eSpeak NG can be used as a service but requires careful licensing consideration for code modifications.
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## Integration Roadmap
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### Phase 1: Stabilization (Weeks 1-2)
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- ✅ Fix Piper absolute paths
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- ✅ Create model documentation
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- ✅ Audit repository
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- [ ] Set up model mirror infrastructure
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- [ ] Document all model sources
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### Phase 2: Quick Wins (Weeks 3-4)
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- [ ] Integrate Silero TTS (actively maintained)
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- [ ] Integrate Chatterbox (emotion control)
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- [ ] Test all models with existing API
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- [ ] Create engine abstraction layer
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### Phase 3: Advanced Features (Months 2-3)
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- [ ] Integrate StyleTTS2 (best quality)
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- [ ] Add Fish Speech support
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- [ ] Implement voice cloning API endpoint
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- [ ] Add emotion/style control API
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### Phase 4: Resilience (Months 3-4)
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- [ ] Complete model mirroring to ai.foxhop.net
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- [ ] Archive critical models to Archive.org
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- [ ] Create fallback download logic
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- [ ] Implement automatic mirror selection
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### Phase 5: Experimental (Months 4+)
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- [ ] Evaluate Maya1 for production
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- [ ] Test Step-Audio-EditX integration
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- [ ] Research Kokoro TTS integration
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- [ ] Implement streaming TTS
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## Raccoon Mission Priorities
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### Critical Rescue Operations 🚨
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1. **Coqui XTTS-v2** - Company shut down, repository archived
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- Action: Mirror all weights (1.8GB)
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- Action: Fork repository to uncloseai-xtts
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- Timeline: Immediate
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2. **Piper TTS** - Original project abandoned
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- Action: Mirror all voices (2GB)
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- Action: Vendor code or create PyPI package
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- Timeline: Week 1-2
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### High-Value Acquisitions ⭐
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1. **Chatterbox** - Active but could be abandoned
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- Action: Monitor development status
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- Action: Mirror models (1.2GB)
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- Timeline: Month 1
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2. **Silero TTS** - Active but should be backed up
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- Action: Mirror all language models (500MB)
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- Timeline: Week 2
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### Research & Watch 👀
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1. **Maya1** - Emerging, evaluate stability
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2. **Kokoro TTS** - New project, monitor adoption
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3. **Step-Audio-EditX** - Experimental, track development
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### Low Priority 📋
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1. **Tortoise TTS** - Too slow, but preserve for quality
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2. **eSpeak NG** - Actively maintained, not at risk
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3. **Mozilla TTS** - Historical archive only
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## Storage Requirements
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### Current Infrastructure
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- Piper voices: ~2GB
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- XTTS v2: ~1.8GB
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- **Total:** ~4GB
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### Planned Integration
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- Silero models: ~500MB
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- Chatterbox: ~1.2GB
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- StyleTTS2: ~2GB
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- Fish Speech: ~1.5GB
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- Kokoro: ~500MB
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- Maya1: ~1.5GB
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- **Total New:** ~7.2GB
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### Complete Mirror Strategy
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- Production models: ~4GB
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- Integration candidates: ~7.2GB
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- Archive/backup: ~8GB (duplicates + older versions)
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- **Total Required:** ~20GB
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## Risk Assessment
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### High Risk - Immediate Action Required
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| Model | Risk Factor | Mitigation |
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|-------|-------------|------------|
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| Coqui XTTS-v2 | Company defunct, repo archived | Mirror weights, fork code |
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| Piper TTS | Original abandoned, fork unstable | Vendor code, mirror voices |
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### Medium Risk - Monitor Closely
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| Model | Risk Factor | Mitigation |
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|-------|-------------|------------|
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| Chatterbox | Company-backed, could pivot | Regular backups, monitor status |
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| Tortoise TTS | Low activity | Mirror weights |
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### Low Risk
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| Model | Status |
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|-------|--------|
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| Silero TTS | Actively maintained |
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| eSpeak NG | Active community |
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| StyleTTS2 | Active research |
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## Technical Architecture Recommendations
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### Engine Abstraction Layer
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```python
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class TTSEngine:
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def synthesize(text: str, voice: str, **kwargs) -> bytes
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def get_voices() -> List[Voice]
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def clone_voice(audio_sample: bytes) -> Voice
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def supports_emotion() -> bool
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def supports_streaming() -> bool
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```
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### Model Selection Strategy
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1. **Fast responses (tts-1):** Piper TTS, Silero
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2. **High quality (tts-1-hd):** Coqui XTTS-v2, StyleTTS2
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3. **Voice cloning:** Coqui XTTS-v2, Chatterbox, Tortoise
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4. **Emotion control:** Chatterbox, Coqui XTTS-v2
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5. **Multilingual:** Coqui XTTS-v2, Maya1, Piper
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6. **Privacy/offline:** Mimic 3, Piper, eSpeak NG
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## Research Methodology
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### Evaluation Criteria
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1. **Quality:** MOS scores, naturalness, prosody
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2. **Performance:** RTF, latency, resource usage
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3. **Features:** Voice cloning, emotion control, multilingual
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4. **Maintenance:** Active development, community support
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5. **License:** Commercial compatibility
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6. **Risk:** Project abandonment probability
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7. **Integration:** Ease of deployment, dependencies
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### Testing Protocol
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1. Install and run basic synthesis
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2. Evaluate audio quality (subjective MOS)
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3. Measure performance (RTF, latency)
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4. Test advanced features (cloning, emotion)
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5. Assess resource requirements (CPU, GPU, RAM)
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6. Review code quality and documentation
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7. Check license compatibility
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## Community & Ecosystem
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### Active Communities
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- **Coqui/XTTS:** Large community, multiple forks
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- **Silero:** Active GitHub, regular updates
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- **eSpeak NG:** Accessibility-focused community
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- **Piper:** Rhasspy ecosystem, home automation
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### At-Risk Projects
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- **Mozilla TTS:** Archived, historical only
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- **Tortoise TTS:** Low activity, mostly complete
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- **Mimic 3:** Mycroft AI restructuring
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### Emerging Projects
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- **Kokoro TTS:** New, gaining traction
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- **Maya1:** Research project, early stage
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- **Step-Audio-EditX:** Cutting edge, experimental
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## Conclusion
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The TTS landscape is rapidly evolving with several high-quality open-source options. However, many projects face abandonment risk, making the Raccoon Mission critical for long-term viability.
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### Key Takeaways
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1. **Immediate Focus:** Secure Coqui XTTS-v2 and Piper TTS through mirroring
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2. **Quick Wins:** Integrate Chatterbox and Silero for feature diversity
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3. **Quality Goal:** StyleTTS2 for best-in-class naturalness
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4. **Diversity:** Maya1 for non-English markets
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5. **Innovation:** Monitor Step-Audio-EditX for future capabilities
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### Success Metrics
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- ✅ All critical models mirrored (0/2 complete)
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- 🎯 3+ production engines integrated (2/3 complete)
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- 🎯 Voice cloning API functional (1/1 complete with XTTS)
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- 🎯 Emotion control available (0/1 complete)
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- 🎯 <100ms latency option (1/1 complete with Piper)
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- 🎯 20GB mirror infrastructure (0% complete)
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---
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**Raccoon Mission Status:** 🦝 2/10 models rescued and integrated
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**Next Action:** Set up mirror infrastructure and integrate Chatterbox
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**Documentation Maintained By:** UncloseAI Speech Team
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**Last Updated:** 2025-11-09
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