---
name: Audio VAD (currently a stub)
type: architecture-map-page
slice: 03-audio-transcription
last_verified: 2026/05/09
---

# Audio VAD (currently a stub)

> **Where you are:** [Architecture map](../README.md) → [Audio + Transcription](README.md) → Audio VAD

**Plain English summary.** `lumotia-audio` exposes a `SpeechDetector` type, but right now its `is_speech()` returns `true` for every input. This is a deliberate stub: both candidate Silero VAD bindings pin an older `ort` version than `transcribe-rs` (Parakeet) requires, so adding either today would force a workspace-wide downgrade. Live capture uses the energy-based `RmsVadChunker` from the transcription crate as the working fallback until the `ort` ecosystem aligns.

## At a glance

- Crate: `lumotia-audio`
- Path: `crates/audio/src/vad.rs`
- LOC: 35
- External deps: none (pulls `VAD_SPEECH_THRESHOLD` from `lumotia_core::constants`).
- Internal callers (best effort): unused in production today. The threshold is read but never compared, because `is_speech` always returns `true`.

Public surface:

- `pub struct SpeechDetector` — `crates/audio/src/vad.rs:14`, derives `Default`.
- `pub fn SpeechDetector::new() -> Self` — `crates/audio/src/vad.rs:19`.
- `pub fn SpeechDetector::is_speech(&self, _samples: &[f32]) -> bool` — `crates/audio/src/vad.rs:26`.
- `pub fn SpeechDetector::threshold(&self) -> f64` — `crates/audio/src/vad.rs:30`.
- `pub fn SpeechDetector::reset(&mut self)` — `crates/audio/src/vad.rs:34`.

## What's in here

The whole file is the stub plus an explanatory header:

> Both `voice_activity_detector` and `silero-vad-rust` pin ort 2.0.0-rc.10 which conflicts with transcribe-rs requiring ort 2.0.0-rc.12. When the ort ecosystem aligns (likely at 2.0.0 stable), add Silero VAD here.
>
> For now, all audio is treated as speech. This matches v0.2 behaviour (no VAD) and doesn't affect core functionality.

The threshold comes from `VAD_SPEECH_THRESHOLD` (slice 5) and is currently dead weight.

## Data flow

`SpeechDetector::is_speech(samples) -> true`. There is no flow.

## Watch-outs

- **The other VAD lives in the transcription crate.** `RmsVadChunker` (see [transcription-streaming.md](transcription-streaming.md)) is the live-capture chunker that actually decides what gets transcribed. When Silero lands here, expect to consolidate the two: the chunker becomes a thin shell around a real VAD predicate.
- **`is_speech` returning `true` is a feature, not a bug.** v0.2 had no VAD at all. The stub keeps the interface stable so callers can switch to a real Silero impl without a code change.
- **Do not reach for `voice_activity_detector` 0.x or `silero-vad-rust` 6.x without a workspace-wide ort audit.** The conflict is documented, has bitten before, and will bite again until upstream `ort` reaches a stable that both crates target.
- **`reset()` is a no-op.** The trait shape exists for future Silero state.

## See also

- [Transcription streaming](transcription-streaming.md) — `RmsVadChunker`, the actual gating today.
- `lumotia_core::constants::VAD_SPEECH_THRESHOLD` (slice 5) — wired but unused.
- `Cargo.toml` of `lumotia-audio` — the commented-out `silero-vad-rust = "6"` line documents the deferred dep.
