OpenAI launched two new Speech to Text models gpt-4o-mini-transcribe and gpt-4o-transcribe in March 2025. These models support streaming transcription for both completed and ongoing audio. Audio transcription refers to converting the audio input to text output (output format would be text or json).The transcription of already completed audio is much simpler using the transcription API provided by OpenAI.
The Realtime transcription is useful in application that require immediate feedback such as Voice assistants, Live captioning, Interactive voice applications, Meeting transcription and Accessibility tools. OpenAI has provided Realtime Transcription API (currently in beta) which allows you to stream audio data and receive transcription results in real-time. The realtime transcription API should be invoked using WebSocket or webRTC. This article focuses on invoking Realtime API using Java WebSocket implementation.