Using Retrotink 4K with Katsukity's Nintendo 3DS Capture Card

As soon as I got over the initial shock of the options RetroTink 4K brings to the retro gaming table, I realized that only 2 out of 30+ retro consoles I own will be left out! My Nintendo DS that’s modified with a Loopy capture card, as well as my Nintendo 3DS that’s using a Katsukity capture card.

Both of these capture cards output video through USB, and use a proprietary software, so I got worried there would be no (cheap) way for me to pass their signal onto the RT4K.

Thankfully, OBS comes to the rescue, since it’s able to send the full output to any external monitor – in this case the RetroTink 4K.

While this guide will focus on Katsukity’s 3DS capture card, the process is almost identical for Loopy’s Nintendo DS capture card.

How to Prepare Your Katsukity Nintendo 3DS

The top screen of the Nintendo 3DS outputs a native resolution of 400 pixels wide, by 240 pixels tall* (5:3 ratio), while the bottom screen is smaller at 320 pixels wide, by 240 pixels tall (4:3 ratio). The combined video output from the Katsukity board is 400×480 (adding black borders to the bottom screen).

*This is only true for capture purposes, since the 3D screen actually outputs double the horizontal pixels (800×240) in order to create the 3D effect.

The “new3DS_view” software for the 3DS, offers the ability to upscale the native signal up to 4 times:

• Size adj – Dot by dot x 1 = 400×480
• Size adj – Dot by dot x 2 = 800×960
• Size adj – Dot by dot x 3 = 1,200×1,440
• Size adj – Dot by dot x 4 = 1,600×1,920

Some comparison screenshots are provided below:

It’s easy to see that the final image is progressively sharper, the higher the scaling on the Katsukity 3DS.

Even though both the Katsukity 3DS and the RetroTink 4K are using no filtering (defaults to integer scaling), we get much cleaner results when scaling more on the 3DS side.

Keep in mind, that we are unable to send a resolution higher than 1,920×1,080 to the RT4K, therefore your OBS preview window will shrink or expand into 1,920×1,080 (or the resolution you set it as), therefore RT4K will always upscale based on that.

For this reason, we get diminishing returns with 3x and 4x, but 2x does offer a major improvement over 1x.

How to Setup OBS

If you don’t already have an OBS Profile & Scene Collection setup for 3DS capture, follow these steps on OBS:

1. Profile -> New. Name it Katsukity_3DS
2. Skip the setup wizard, and go to File -> Settings.
3. Go to Video -> Base (Canvas) Resolution, and input either 400×480, or 800×960 depending on your choice. Ensure the Output (Scaled) Resolution is the same, and FPS set to 60.
4. Scene Collection -> New. Name it Katsukity_3DS
5. Make sure the new3DS_view software is running, and properly receiving your 3DS video & audio.
6. Go to Sources on the bottom left, and add a new Game Capture source. Again, I suggest naming it Katsukity_3DS so that’s easy to find it later on in different scene collections.
7. Choose Mode -> Capture specific window, and Window -> [new3DS_view(x64).exe]
8. You should now be able to preview your feed in OBS properly. If not, make sure you have followed all the steps correctly, and that the resolution outputted from the 3DS software, is the same as the one you chose in OBS’ video settings.

How to Send Video from OBS to Retrotink 4K

All you have to do next:

1. Insert an HDMI 1.4 (or higher) into one of your GPU’s free HDMI outputs (if you don’t have any, and you only have display ports available, you can use a Display Port to HDMI adapter, or DP to HDMI cable).
2. Insert the output of this cable into Retrotink 4K’s HDMI input (or your HDMI switcher that leads into RT4K’s input).
3. Right-click your Desktop, and go to Display Settings, choose the new “monitor”, and choose the Display Resolution as 1920×1080.
4. Right-click the Preview section in OBS, and Choose Full-screen Projector (Preview) -> \\.\DISPLAY.

Ta-da!

Your OBS feed should be passed successfully onto the Retrotink 4K for further processing and enjoyment!

Stability Issues With Video Feed

Sadly one major issue I’m still trying to iron out, is losing the video feed constantly.

Every 10-60 seconds, I will get a black screen, and then instantly get the feed back.

This is super annoying of course, and makes capturing video content effectively impossible.

Please let me know if you have a workaround for this, and I will certainly update this guide once I find one.

I’m suspecting the source of the issue is around the fact we are sending the signal straight from the GPU to the Retrotink, without a real Display Monitor in between.

My technical expertise around these matters is limited though sadly, so it will take a while for me to figure it out!