WhisperX: Time-Accurate Speech Transcription of Long-Form Audio

Large-scale, weakly-supervised speech recognition models, such as Whisper, have demonstrated impressive results on speech recognition across domains and languages. However, the predicted timestamps corresponding to each utterance are prone to inaccuracies, and word-level timestamps are not available out-of-the-box. Further, their application to long audio via buffered transcription prohibits batched inference due to their sequential nature. To overcome the aforementioned challenges, we present WhisperX, a time-accurate speech recognition system with word-level timestamps utilising voice activity detection and forced phoneme alignment. In doing so, we demonstrate state-of-the-art performance on long-form transcription and word segmentation benchmarks. Additionally, we show that pre-segmenting audio with our proposed VAD Cut & Merge strategy improves transcription quality and enables a twelve-fold transcription speedup via batched inference. The code is available open-source(1).