FR-2: Audio Capture

Captures microphone input suitable for Whisper transcription.

Requirement

1. Capture 16 kHz mono audio via the cpal crate.
2. Default maximum duration 10 s; user-configurable up to 30 s.
3. Recording stops automatically when the duration limit is reached or the user presses the hot-key
4. again.
5. Audio is buffered entirely in memory; no files are written to disk.
6. Handle microphone permission prompts gracefully on first run.

Rationale

Lower sample-rate mono audio minimises processing cost while meeting Whisper’s input requirements.

Acceptance Criteria

• Recording initialises within 100 ms after hot-key press.
• Audio stream conforms to 16 kHz, 16-bit, mono.
• User can change max duration in Settings; value persists across restarts.
• Recording stops cleanly at limit without crashing or clipping.
• Permission dialog appears once and records decision.

Test-Driven Design

Adopt test-driven development: begin by writing failing unit/integration tests that assert each Acceptance Criterion. Only then implement capture logic until tests pass in CI.

References

PRD §6 Functional Requirements – FR-2