Microphone track stops when the input device changes during a recording #208

BetterCapture 2026.4 · macOS 26.6.2 · MacBook Pro, Apple Silicon

Steps

1. Start a recording with AirPods as the microphone.
2. Switch the input to the built-in MacBook microphone (or take the AirPods out).
3. Keep recording.

Expected: the microphone track continues on the new device, or silence is written for the gap.

Actual: the video runs to the end (10 min 14 s), but the microphone track ends at the moment of the switch (65 s). Nothing is written after it, not even silence. The system audio track is fine.

Looking at v2026.4: the mic comes from SCStreamConfiguration.captureMicrophone, but nothing observes a default-input change or the capture device going away, and AssetWriter.appendMicrophoneSample returns silently when the input is not ready and pads silence only at the start of the track. A listener on kAudioHardwarePropertyDefaultInputDevice that reconfigures the stream, plus silence padding for mid-recording gaps, would cover it.

Possibly related: on another Mac running 2026.3, with the microphone pinned to the built-in device, the mono mic was written to the left channel only (right channel was digital silence). Clearing the pinned device fixed it.