---
pipeline_tag: voice-activity-detection
license: bsd-2-clause
tags:
  - speech-processing
  - semantic-vad
  - multimodal
  - video
---
# Smart Turn Multimodal

**Smart Turn Multimodal** is a multimodal extension of Pipecat's Smart Turn that combines audio and video to predict whether a speaker has finished their turn. Visual cues (mouth movement, gaze) help disambiguate pauses that are ambiguous in audio alone.

## Links

* [Blog post: Smart Turn Multimodal](https://susurobo.jp/blog/smart_turn_multimodal.html)
* [GitHub repo](https://github.com/susurobo/smart-turn-multimodal) with training and inference code
* Original audio-only [Smart Turn v3](https://huggingface.co/pipecat-ai/smart-turn-v3)

## Model architecture

* **Audio branch:** Whisper Tiny encoder (8s context) with cross-attention pooling → 384-dim embedding
* **Video branch:** R3D-18 (Kinetics-400 pretrained) processing last 32 frames (~1s) → 256-dim embedding  
* **Fusion:** Late fusion via concatenation + linear projection back to 384-dim
* Params: ~20M total
* Checkpoint: ONNX available

## Audio-only fallback

When video is unavailable, pass `None` for `pixel_values`. The model uses a zero tensor internally, falling back to audio-only behavior—no code changes required.

## How to use

```python
from inference_multimodal import predict_endpoint

result = predict_endpoint(audio_array, video_path="clip.mp4")
# result = {"prediction": 1, "probability": 0.92}

# Audio-only fallback
result = predict_endpoint(audio_array, video_path=None)
```

## Limitations

- **Dataset variety:** Currently trained on Meta's [Casual Conversations dataset](https://ai.meta.com/datasets/casual-conversations-dataset/) (mostly unscripted monologues). Generalization to diverse conversation styles is still being validated.
- **VAD-triggered:** Model is activated by VAD-detected silence, not predictive of turn endings before silence occurs.

## Thanks

Thank you to Pipecat for the original Smart Turn model and to Meta for the Casual Conversations dataset.