A GDExtension that publishes the contents of a SubViewport as a live video source other applications can pick up. OBS, Resolume, TouchDesigner, VJ tools, or a second process of your own can receive it, with no window or screen capture involved.

A typical use is a spectator or broadcast camera: a second camera renders into a SubViewport at its own resolution and frame rate, and a streaming tool receives that view without it ever appearing on screen.

Each platform uses its native video sharing system:

Usage

1. Add a SubViewport with a camera inside it, at the resolution you want to stream. Set its update mode to Always.
2. Add a SpectatorStreamExporter node and point target_viewport at the SubViewport.
3. Set active = true from code (in _ready() or later):

@onready var exporter: SpectatorStreamExporter = $SpectatorStreamExporter

func _ready() -> void:
    exporter.stream_error.connect(func(msg): push_warning("Spectator stream: " + msg))
    exporter.active = true

Properties: target_viewport, stream_name (what receivers see), active, target_fps (cap the stream rate independently of the game). Methods: restart() (call after resizing the SubViewport). Signals: stream_started, stream_stopped, stream_error(message).

Features

• One node, no scene rewiring
• Independent resolution and frame rate from the game
• Drop-oldest frame queue, so a slow receiver never stalls your game
• Null backend for testing without a receiver (SPECTATOR_STREAM_NULL_BACKEND=1)
• Optional debug logging (SPECTATOR_STREAM_DEBUG_LOG=1)
• Demo project included

Requirements

• Godot 4.7 or newer
• Forward+ or Mobile renderer. The Compatibility (OpenGL) renderer isn't supported, because frames are read through the RenderingDevice.
• Linux: a running PipeWire daemon. Windows: a D3D11-capable GPU (no extra DLLs needed, Spout is compiled in). macOS: Syphon.framework available to the extension.

Platform status

• Linux (PipeWire): tested with OBS
• Windows (Spout): tested
• macOS (Syphon): built against the SDK but not tested on real hardware, so bug reports are welcome

Performance note. Frames are read back through the CPU (about 8 MB per 1080p frame, roughly 500 MB/s at 1080p60). Use target_fps and a sensible viewport size on modest hardware.