Text To Speech Updates & Release Notes

Launched Realtime TTS-2 (inworld-tts-2), our most powerful and expressive TTS model:

• Natural Language Steering: Direct any voice with bracketed instructions like [say excitedly], [whisper in a hushed style], or free-form directions like [speak as if barely holding back rage]. Covers articulation, intonation, volume, pitch, range, speed, vocal style, and non-verbals ([laugh], [sigh], etc.). See the Steering guide.
• Stronger Multilingual Support: Production-quality synthesis across 15 languages, plus experimental support for 90+ additional languages. See Languages.
• Cross-Lingual Voice Synthesis: Reuse the same voice across multiple languages. For best results, specify the language field.
• Voice Localization: Localize your voice for the most consistent, native-sounding speech in a target language. See Voice Localization.
• Delivery Mode: New deliveryMode field (STABLE, BALANCED, EXPRESSIVE) controls the trade-off between consistency and emotional range.
• Updated Voice Design: Released an updated version of Voice Design with improved generations. See Voice Design.

Launched Inworld TTS 1.5, our newest generation of realtime TTS models featuring:

• Two New Models: Our flagship model inworld-tts-1.5-max is ideal for most use cases, with the best balance of quality and speed. For use cases where latency is the top priority, we also offer inworld-tts-1.5-mini.
• Latency Improvements: Our new TTS-1.5 models achieve P90 latency for first audio chunk delivery under 250ms for our Max model and under 130ms for our Mini model, a 4x improvement compared to TTS-1.
• More Expressive and More Stable: TTS-1.5 is 30% more expressive than prior generations and demonstrates a 40% reduction in word error rates.
• Additional Languages: We've added support for additional languages, including Hindi, Arabic, and Hebrew, bringing total languages supported to 15.

Released an upgraded version of the Inworld TTS models with higher overall quality.

• Speech Quality: Clearer, more natural speech with smoother pacing and more accurate pronunciation.
• Voice Similarity: Cloned voices sound closer to the originals, preserving each voice’s unique style.
• Non-English Languages: More consistent, reliable output across supported non-English languages.
• Custom Pronunciation: New support for inline IPA, giving you control over exact word pronunciations. See the Key Features for details.