Enable 'stretch video to full-screen' feature/setting in Moonlight settings for 3D Full-SBS for AR glasses such as XReal Air

[mvillarg]

Is your feature request related to a problem? Please describe. This request is aimed to "easily" unleash 3D Full-SBS gaming capabilties when Moonlight client is paired with a set of AR glasses such as XReal Air.

Problem is, the hardware/firmware of these type of glasses is very basic, so they cannot convert 3D Half-SBS output coming from Sunshine (i.e 3840x2160 containing 2 frames for both left and right eyes, each one taking 1920x2160 resolution) to their native 3D Full-SBS res of 3840x1080, this is 1920x1080 per eye. In short, they cannot resize/squeeze the bigger frame height from 2160 to 1080 pixels.

Full-SBS only work for a few games (via Geo-11 fix or post-process effect via Reshade + SuperDepth3D) that can handle 3840x1080 resolution. So the idea is to have Geo-11 or Reshade do its own magic at standard 16:9 aspect ratio in whatever resolution (ideally 3840x2160 for best picture quality, but other resolutions such as 3200x1800 or 2560x1440 would also be welcome) and then having Moonlight on the client side streching that image to 3840x1080 / 32:9 aspect ratio (so basically, squeezing height by half).

Right now what's happening is that Moonlight is maintaining the aspect ratio of the source signal (Sunshine) and centering the image, so black bars appear at both sides of the screen, hence ruining the 3D experience!

Describe the solution you'd like It would be nice to have the 'stretch video to full-screen' setting (as in Android's version of Moonlight) in the Windows (aka QT) version too, so that 3D Full-SBS can be achieved when streaming to a client with AR glasses attached (such as XReal Air) at its native 3D resolution of 3840x1080.

Describe alternatives you've considered

Additional context

[mvillarg]

Watching at the code I saw this at moonlight-qt/app/streaming/video/ffmpeg-renderers/d3d11va.cpp > D3D11VARenderer::setupRenderingResources()

---

    // Scale video to the window size while preserving aspect ratio
    SDL_Rect src, dst;
    src.x = src.y = 0;
    src.w = m_DecoderParams.width;
    src.h = m_DecoderParams.height;
    dst.x = dst.y = 0;
    dst.w = m_DisplayWidth;
    dst.h = m_DisplayHeight;
    StreamUtils::scaleSourceToDestinationSurface(&src, &dst);

    // Convert screen space to normalized device coordinates
    SDL_FRect renderRect;
    StreamUtils::screenSpaceToNormalizedDeviceCoords(&dst, &renderRect, m_DisplayWidth, m_DisplayHeight);

    VERTEX verts[] =
    {
        {renderRect.x, renderRect.y, 0, 1.0f},
        {renderRect.x, renderRect.y+renderRect.h, 0, 0},
        {renderRect.x+renderRect.w, renderRect.y, 1.0f, 1.0f},
        {renderRect.x+renderRect.w, renderRect.y+renderRect.h, 1.0f, 0},
    };

---

A separate approach should be taken when enabling 'stretch video to full-screen' in Moonlight settings:

    // DO NOT scale!
    SDL_Rect dst;
    dst.x = dst.y = 0;
    dst.w = m_DisplayWidth;
    dst.h = m_DisplayHeight;

    // Convert screen space to normalized device coordinates
    SDL_FRect renderRect;
    StreamUtils::screenSpaceToNormalizedDeviceCoords(&dst, &renderRect, m_DisplayWidth, m_DisplayHeight);

    VERTEX verts[] =
    {
        {renderRect.x, renderRect.y, 0, 1.0f},
        {renderRect.x, renderRect.y+renderRect.h, 0, 0},
        {renderRect.x+renderRect.w, renderRect.y, 1.0f, 1.0f},
        {renderRect.x+renderRect.w, renderRect.y+renderRect.h, 1.0f, 0},
    };

[mvillarg]

I implemented the above change locally and I can confirm IT JUST WORKS AS EXPECTED :-)

The one thing missing in the implementation is the physical/visible option on the Settings menu, though my QT skills are not there just yet!

The way this works in practical terms is as follows (this is for Windows 11, in Linux/Steam OS might differ): 1) Recommended step: Install Virtual Display Driver and set these resolutions that will later be used in the games (all them are 16:9 aspect ratio). Depending on how beefy our GPU is, we could play at glorious 4K or lower down until constant 60 fps is achievable.

• 1920x1080@60hz (this would act as pure HALF-SBS, so that vertical resolution will be matching our AR screens but horizontal will just fill half of the pixels of the displays, causing kind of a blurry image but you can get used to it after 5 minutes of gameplay).
• 2560x1440@60hz (still blurry image despite having more vertical pixels)
• 2880x1620@60hz (good compromise between performance and PQ)
• 3200x1800@60hz (very good quality and less GPU taxing by around 25% compared to 4K)
• 3840x2160@60hz (ultra sharp clarity since we're matching 1-to-1 horizontal pixels while performing some kind of supersampling/bialiasing over the vertical lines. This is hands down the best picture quality you can get out of this class of AR glasses!) 2) Open modified version of Moonlight (with the change described above) with AR glasses set to 2D mode (display resolution at this point doesn't matter, though by default would be set to 1920x1080 which is the current standard for this type of glasses). 3) On Moonlight Settings set 4K resolution at 60 fps (more than 60hz/fps would be useless as of today this kind of AR glasses theoretically don't have enough bandwidth to output that many pixels at more than 60hz). 4) Enter your host PC through Desktop mode (PC host display resolution is irrelevant at this point). 5) Launch any game that supports stereoscopic 3D via Geo 11 driver or Reshade + SuperDepth3D. 6) Switch to 3D-SBS mode (on XReal Air 2 for example, you just press the brigthness+/volume+ for 2 seconds). 7) Enjoy the 3D experience! :-)