AssemblyAI Voice Agent API

AssemblyAI is a voice AI infrastructure platform that provides APIs and models for transcribing, understanding, and interacting with speech. Its products include pre-recorded, realtime, and synchronous speech-to-text APIs; speech understanding for capabilities such as speaker identification, sentiment, chapters, and summaries; inline audio and transcript guardrails; an LLM Gateway with fallback; and a Voice Agent API with turn detection and interruption handling. The platform can combine speech-to-text, an LLM, and text-to-speech into a real-time voice-agent stack, and supports voice applications such as notetakers, call analytics, medical transcription, dictation, agent assist, and AI scribes. AssemblyAI states that its speech-to-text APIs support 99 languages and that its infrastructure processes about 2 million hours of audio per day.

An AI voice-agent platform for building and deploying phone-based conversational agents. It supports agents that conduct automated interviews and other business conversations over telephone calls.

Smallest AI is a voice-AI platform offering text-to-speech, speech-to-text, speech-to-speech, and orchestrated voice-agent models for real-time deployments.

Speech To Speech is an open-source, modular voice-agent pipeline from Hugging Face. It chains voice activity detection, speech-to-text, a language model, and text-to-speech as separate stages connected by queues; each stage has interchangeable backends. The language-model stage supports OpenAI-compatible protocols and can use hosted providers, Hugging Face Inference Providers, vLLM, or llama.cpp, while the system streams transcripts, generated text, tool calls, and synthesized audio. The project exposes the core OpenAI Realtime event set through WebSocket and WebRTC and includes commands for running a realtime server, a microphone-and-speaker client, or a local setup. It is distributed as a Python package and requires Python 3.10 or newer. The repository says the pipeline is used as the conversation backend for Reachy Mini robots.

ElevenLabs is an AI voice and audio platform offering text-to-speech, voice generation and cloning, speech-to-text transcription, dubbing, music generation, and voice agents. Its transcription capability produces timing information for video cuts, subtitles, and synchronized animations. It provides more than 5,000 voices across more than 90 languages, supports custom voice clones, and offers secure APIs and SDKs through ElevenAPI. ElevenCreative supports content creation, while ElevenAgents supports customer-experience applications.