VAD (Voice Activity Detection)

VAD is the first signal-processing stage in a transcription pipeline. It scans the incoming audio and emits a binary flag per short window: speech or no speech. Without VAD, ASR and diarization waste compute on silence, music, room tone, and background hum, and they hallucinate text in those regions.

VAD models are tiny by design - a few hundred kilobytes - because they run continuously over the full audio stream. Mac Note Taker uses FluidAudio's VAD, which sits on the CPU and consumes roughly 0.5% of one core during a meeting. The boolean output gates whether the downstream Parakeet ASR and pyannote diarization models are invoked at all.