# Spout Input

**Spout** is a Windows-native GPU texture-sharing framework that lets any Spout-capable application share its rendered output directly as a live video source in Exaplay 3 — with zero latency and zero compression, because the texture never leaves the GPU.

![Spout source in File Browser](/files/YagRgCr41QoPJKCCHXqM)

## What Is Spout?

Spout (developed by Lynn Jarvis) enables real-time sharing of OpenGL textures between applications on the same Windows PC. Popular Spout senders include:

| Application                        | Use case                                  |
| ---------------------------------- | ----------------------------------------- |
| **Resolume Avenue / Arena**        | VJ software sending to Exaplay for output |
| **TouchDesigner**                  | Generative / interactive content          |
| **OBS Studio** (with Spout plugin) | Streaming software output                 |
| **Unity / Unreal Engine**          | Real-time 3D content                      |
| **Processing**                     | Creative coding                           |

Because the texture lives on the GPU, Spout has effectively **zero CPU overhead** and **zero latency** — the frame appears in Exaplay the moment the sender renders it.

## Adding a Spout Source

1. Open the **File Browser** → **Live Feeds** tab.
2. A generic **Spout Input** entry is always visible, even when no Spout sender is running. This allows preprogramming your show in advance.
3. Any currently active Spout senders also appear individually (e.g. *Spout: MyApp*).
4. Drag **Spout Input** (or a specific sender) onto a track in the Timeline.

> **Tip:** Use the generic **Spout Input** when preprogramming — it connects to whatever sender becomes active later. Use a named sender entry when you need a specific source.

> **Note:** Spout requires `SpoutLibrary.dll`, which is included in the Exaplay installation. No separate SDK install is needed.

## Selecting a Sender

If multiple Spout senders are active, each appears with its sender name as a separate item in the Live Feeds list. The sender name is set by the originating application.

To switch a running Spout clip to a different sender:

1. Select the Spout clip in the Timeline.
2. In the Inspector, use the **Spout Sender** drop-down to choose a different active sender, or select **Any Sender** to connect to whatever is currently broadcasting.
3. The switch is hot — Exaplay seamlessly transitions to the new sender without interrupting playback.

## Saving & Loading Spout Clips (VPP)

Spout clips are fully saved in VPP project files:

* The selected sender name (or "Any Sender" mode) is preserved.
* On project load, each Spout clip reconnects to its saved sender automatically.
* If the sender is not yet running, the clip waits and reconnects when the sender starts.

## Behaviour When the Sender Disconnects

If the Spout sender stops or closes while Exaplay is using it:

* The output clears to **black** automatically.
* A warning is logged to the engine log (`Documents\Exaplay3\logs\`).
* When the sender restarts, Exaplay reconnects automatically without any user action.

## Sender Size Changes

If the Spout sender changes its output resolution (e.g. a window resize), Exaplay detects the new dimensions on the next frame and resizes its internal texture buffer automatically. No manual reconfiguration is needed.

## Performance

| Metric             | Typical value          |
| ------------------ | ---------------------- |
| Latency            | < 1 frame (GPU direct) |
| CPU overhead       | < 1 %                  |
| GPU overhead       | \~0.5 % (texture copy) |
| Maximum resolution | Limited by GPU VRAM    |

## Comparison: Spout vs NDI vs Capture Card

| Method           | Latency    | CPU      | Cross-machine  | Compression        |
| ---------------- | ---------- | -------- | -------------- | ------------------ |
| **Spout**        | < 1 frame  | Minimal  | ❌ Same PC only | None (GPU texture) |
| **NDI**          | 1–3 frames | Moderate | ✅ Network      | Low (NDI codec)    |
| **Capture card** | 1–4 frames | Low      | ✅ HDMI         | None (raw)         |

Use Spout when the source application runs on the same machine as Exaplay and you need the absolute lowest latency.

## Identifying Spout Clips

Spout clips show a distinctive **Spout icon** (a waveform-style "S" logo) in:

* The File Browser Live Feeds tab
* Timeline segment thumbnails
* The CueList composition view


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