AssemblyAI

Production speech-to-text. The STT default for many companies.

End-to-end speech recognition platform — real-time streaming, batch transcription, speaker diarization, and language detection. Strong on accented speech, telephony audio, and long-form recordings.

Text-to-speech, voice cloning, and multilingual dubbing.

Hosted speech synthesis at near-human quality — TTS, voice cloning, multilingual dubbing, and conversational voice agents. Default choice when you need a voice that sounds like a person, not a robot.

Low-latency streaming text-to-speech for real-time voice.

Streaming-first speech synthesis built around the Sonic family of state-space models. Aims at real-time agent voices where latency between turns is the product. Strong choice for sub-200ms voice loops.