GPU Output

GPU output routes a display's rendered pixels to a physical connector on the Runner node's graphics card — HDMI, DisplayPort, or any other connector the GPU exposes. In WATCHOUT, GPU is one of the five output devices alongside SDI, ST 2110, NDI®, and Virtual. It is the default routing for new displays.

GPU is the right choice when the receiving device — a monitor, projector, LED processor, or capture card — accepts a standard display connector and you do not need network transport or broadcast-grade timing. It supports the widest set of color depths and color spaces, including HDR formats.

Configuring a GPU Display

To set up a display for GPU output:

  1. Select the display in the Stage or Device list.
  2. In Device Properties → Output, set the Output Type to GPU (this is the default).
  3. Assign the Channel number corresponding to the physical connector on the node.
  4. Set the Resolution to match the connected device's native raster.

Channel Assignment

The Channel property is an index into the operating-system enumeration of GPU outputs on the Runner node. Each physical connector on the GPU corresponds to one channel. Channels are numbered across all GPUs in the node, not per GPU — with two GPUs each driving four outputs, channels 1–4 might belong to one GPU and 5–8 to the other. The exact ordering follows the OS display enumeration, which depends on PCIe slot order and driver behavior.

Keep channel numbers stable. Windows can renumber displays when a cable is unplugged, reconnected, or a monitor is power-cycled — and the new numbering moves WATCHOUT content to the wrong physical output. The reliable fix is EDID emulation: make Windows believe a monitor is permanently attached to each port, so the desktop layout never changes. On NVIDIA outputs, WATCHOUT can emulate EDID directly — see EDID below. On AMD outputs, enable EDID emulation in the AMD driver settings. If EDID emulation is not practical for your install, see the fallback environment variable in Locking Display Output Channel Numbers.

If two displays on the same node share the same channel, WATCHOUT reports a resource conflict.

Resolution

Choose a preset from the Resolution dropdown or select Custom and enter explicit width and height. The presets cover VGA, HD-720, HD-1080, WUXGA, and UHD-4K. The resolution must match the connected device's native raster — a mismatch produces a stretched or scaled image at the GPU's output, not at WATCHOUT's rendering stage.

Color Depth

GPU output supports the full color depth range:

  • 8-bpc (8 bits per component) — 256 levels per channel. Default.
  • 10-bpc — 1,024 levels per channel. Recommended for HDR output and wide-gamut content.
  • 12-bpc — 4,096 levels per channel. Available where the connected hardware accepts it.
  • 16-bpc — 65,536 levels per channel. The highest precision available.

SDI, ST 2110, and NDI support a narrower set of depths. See the comparison table in Adding Displays.

Color Space

GPU output supports the widest color space selection of any routing type:

  • sRGB — the standard color space for computer displays.
  • sRGB (gamma 2.2) — sRGB primaries with a pure 2.2 gamma curve. Default for new displays.
  • Rec. 601 — legacy SD broadcast.
  • Rec. 709 — HD broadcast standard.
  • Rec. 2020 — wide-gamut UHD/4K SDR.
  • Rec. 2100 HLG — HDR with Hybrid Log-Gamma.
  • Rec. 2100 PQ — HDR with Perceptual Quantizer.
  • Rec. 2100 PQ (HDR10) — PQ with HDR10 static metadata (MaxCLL, MaxFALL).

See HDR and Color Management for the full color pipeline and the trade-offs between these options.

EDID

EDID (Extended Display Identification Data) is a data block that displays transmit to identify themselves and advertise their supported timings. The EDID row is available only for GPU output, and EDID emulation is supported on NVIDIA GPUs only. On AMD hardware, use the AMD driver's EDID emulation settings instead.

The EDID dropdown offers three modes:

  • Current Monitor — use the live EDID from the connected display hardware. This is the default behavior.
  • Keep — do not send any EDID override.
  • A saved EDID asset — apply a previously captured EDID block from the show's asset library.

To capture the connected monitor's EDID as an asset, click Save EDID. The display must be enabled for the Save button to be active.

Captured EDIDs serve two main purposes:

  • Documenting and reproducing a venue's monitor configuration — useful in rental and staging environments, or when troubleshooting cases where a display advertises the wrong modes.
  • Keeping the Windows desktop layout constant. Applying a saved EDID makes the GPU present a permanent, known monitor to Windows regardless of whether the physical display is actually connected and powered on. Windows then keeps the display in its enumeration with stable IDs, so WATCHOUT channel numbers don't shift when cables are unplugged or monitors power-cycled.

Max Quality Mode

The Render with maximum quality toggle forces 16-bit color precision during compositing. It has a visible effect only on 8-bpc outputs — higher bit-depth outputs already composite in higher precision. Disable it on integrated GPUs where the extra precision is not needed, to reduce pixel bandwidth.

Frame Delay

The Delay Frames setting (0–10 frames) adds a configurable output delay. Each frame of delay adds one buffer to the rendering pipeline before the pixels are sent to the GPU output.

Use this to align WATCHOUT outputs with the latency of downstream processors (LED walls, video switchers) so all signals reach the viewer at the same time.

NDI Calibration Stream

GPU displays expose a Calibration Stream field in the Calibration section — the name of an NDI® stream a camera-based alignment system sends test patterns to during calibration. The external system drives the process over the HTTP API. See Display Calibration for the setup and runtime flow.

NDI® is a registered trademark of Vizrt NDI AB.

Previous Next