Display and image quality

The EGL renderer is the supported client renderer and is selected automatically. The older OpenGL renderer is deprecated, does not provide direct DMA imports or native HDR, and should only be used to diagnose a compatibility problem.

Wayland and X11 are both built by default. Automatic selection prefers Wayland when WAYLAND_DISPLAY is set, then X11 when DISPLAY is set. To force X11 from a Wayland session for diagnosis, preserve DISPLAY and unset WAYLAND_DISPLAY for the client process.

Window and guest resolution

With the IDD, win:setGuestRes=yes asks Windows to match the client viewport when its size changes. Press ScrLk + = to request the current size immediately. The IDD creates this as its dynamic ExtraMode using the default refresh configured in the IDD helper.

If a requested resolution does not fit in IVSHMEM, the IDD refuses it and the helper reports the required size. See Determining memory.

Useful window options include:

win:autoResize

Resize the client window when the guest resolution changes.

win:keepAspect

Preserve the guest aspect ratio while resizing.

win:fullScreen

Start in borderless full-screen mode.

win:rotate

Rotate the image by 0, 90, 180 or 270 degrees.

Scaling and filters

The overlay’s EGL filters page controls scaling, sharpening and custom processing. Filters run from top to bottom and can be reordered. Save useful combinations as named presets, then select one at startup with egl:preset.

The built-in filters include:

  • a configurable downscaler;

  • AMD FidelityFX Super Resolution (FSR); and

  • AMD FidelityFX Contrast Adaptive Sharpening (CAS).

The egl:scale option selects automatic, nearest-neighbor or linear scaling when a filter does not provide the required scaling. Additional mpv-style GLSL shaders may be loaded from eglFilter:glslPath. The Anime4K project provides compatible GLSL filters.

HDR

The IDD exposes HDR only when the Windows runtime provides the required IddCx interfaces and the IDD is using a hardware render adapter. This normally means a compatible Windows 11 guest. Windows 10 and IDD software processing remain on the SDR path.

Native HDR output on Linux requires all of the following:

  • the EGL renderer;

  • a Wayland compositor with color-management-v1 support;

  • an HDR-capable monitor and output configuration; and

  • a host graphics driver that can present the required color format.

With egl:mapHDRtoSDR=yes the client tone-maps HDR frames for an SDR desktop. Use egl:peakLuminance to describe the SDR display target and egl:maxCLL to limit the assumed content light level.

X11 presentation is SDR. The EGL renderer tone-maps HDR to SDR there by default. Native Wayland PQ output also requires compositor support for ST 2084 and BT.2020, while scRGB requires compositor scRGB support.

Presentation latency

The defaults favor low latency rather than conventional buffered rendering. Do not enable egl:vsync or egl:doubleBuffer merely to chase a reported frame-rate number; either can add presentation delay. Use the timing graphs to confirm the result on the actual compositor and GPU.

win:jitRender delays rendering toward the expected presentation deadline. It can reduce the age of a frame at display time, but depends on stable timing. Leave it disabled while diagnosing stalls or an unstable refresh cadence.