N64 VI Filter

The N64's RDP chip includes a Video Interface (VI) stage that prepares the video for the final output. From the N64 Programming Manual:

The video interface reads the data out of the framebuffer in main memory and generates the composite, S-video, and RGB signals. The video interface also performs the second pass of the antialias algorithm. The video interface works in either NTSC or PAL mode, and can display 15- or 24-bit color pixels, with or without filtering, at both high and low resolutions. The video interface can also scale up a smaller image to fill the screen.

These functions can make a very big impact on the final image of an N64 game, and the ParaLLEl-N64 libretro core exposes the ability to toggle the postprocessing effects of this stage on and off. Turning it off nets you a few frames per second of speed but also gives us a peek behind the VI curtain:

Filtered

Unfiltered

So, you can see that the filter just barely touches the HUD elements but it does some pretty dramatic stuff to the rest of the image. It applies strong antialiasing to the outside edges of objects, which has a big, noticeable effect (so noticeable, you can see it in the thumbnail images) on Mario's hat and the silhouette of the tree, and it does some blurring that smooths out the dithering that is very visible in the unfiltered shot. On actual hardware, the blurring can be toggled off in some games (Quake II, for example, IIRC) or using Gameshark codes. I believe consoles modded with UltraHDMI or etim's N64RGB boards can also switch it off through the boards' firmwares.

RetroArch Overlay Borders

RetroArch has long had support for fun borders/backgrounds that can fill the unused black space on HDTVs using a specially crafted shader combined with an image, as described in a previous post. However, this system can be finicky and it isn't very forgiving of different screen sizes and aspect ratios. There is another way to achieve a similar outcome, though, using RetroArch's built-in overlay system.

Gameboy border pictured with Harlequin's Gameboy shader

This system was designed to provide onscreen touch controls for the Android and iOS ports of RetroArch, but we can use the same hooks on PC to display our borders. All you have to do is add this to the bottom of your retroarch.cfg:

input_overlay = "/path/to/overlay.cfg"

You can also load overlays directly from the in-game RGUI menu under Settings > Overlay Options.

The overlay.cfg file is extremely simple, containing only 4 short lines (you can either copy these into a blank text file yourself or use the one I include in the download at the bottom of the post):

overlays = 1
overlay0_overlay = border.png
overlay0_descs = 0
overlay0_fullscreen = true 

This file tells RetroArch that there will only be 1 overlay, which image to load as the border (in this case, border.png, located in the same directory as the overlay.cfg), that there will be no buttons attached to the overlay (that is, for touchscreen controls) and that it will take up the full screen, including any black space.

In addition to these border effects, you can also use this system to apply semi-transparent overlay effects, such as scanlines, which can be useful in very low-power settings, such as on Raspberry Pis, homebrew-capable Nintendo Wiis or older cell phones that can't handle even lightweight scanline shaders. Even some MAME "rgb" effects can be used with this system with minor modification.

This system will work fine with the borders from my previous post, and here's a bunch more (formatted for 1920x1200 displays) from NeoGaf user richisawesome.

Here is the download (contains border.cfg, two example borders and an integer scale Cg shader, though the shader should not be necessary now that you can force integer scaling through RGUI):

http://www.mediafire.com/download/1fpa407519jg2hu/overlay-borders.zip

UPDATE (06/02/2014): You can also check out RetroArch's overlay repository on github.

Getting Started with RetroArch

Update (4/23/2012): SSNES has changed its name to reflect its versatility beyond SNES emulation. The new name is RetroArch and this article has been updated to reflect the change.

RetroArch is a multi-platform multi-emulator with support for some really cool, unique features, including extensive shader and filter support, real-time rewind, lossless video dumping, advanced "lagless" netplay, and more. Unlike many other emulators, RetroArch is under rapid and active development and receives new features on a regular basis. However, all of these esoteric options and capabilities can be daunting to new users, so this guide will cover the basics. The instructions are primarily geared toward Windows users, but the configuration information is essentially the same on any platform.

So, first off: RetroArch is all about modularity, so we need to download a couple of initial modules, namely the RetroArch executable and its helper libraries. To get started, go to the RetroArch homepage and download the RetroArch full package that suits your system (the 'x86' build will work on all machines, while the x64 build will only work in 64-bit versions of Windows; get the x86 version if you don't know which is appropriate for you). The slim package contains the absolute minimum required for bare, no-frills emulation, while the full package is prepared to utilize RetroArch's many advanced features.

Once your download finishes, extract the zip file, navigate to the extracted RetroArch folder and look for retroarch-phoenix.exe. This is the graphical user interface (GUI) module that will help us get RetroArch set up and configured. Double-click it and you should see a window that looks like this:

Along the upper edge of the window, open the RetroArch menu and select Update RetroArch:

It should open a window that looks like this:

You can use this tool to automatically download updates for RetroArch, its helper libraries and any/all of the various emulation cores. First off, you'll need to select which flavor of RetroArch you're using--x86 or x64 (aka x86_64)--by clicking on the appropriate bubble next to CPU.

Then, click on the button labeled Check version. This will search for updates to RetroArch and/or its helper libraries and populate the list of available emulation cores:

After that, click on the bubble labeled Redist and then the button that says Download RetroArch. This will fetch any updated RetroArch executables, as well as fresh copies of all of the helper libraries (you can update RetroArch without the helper libraries by using the Full button instead of Redist).

At this point, you can also automatically download any of the cores in the list by double-clicking on its entry. After the download finishes, it will ask if you want to use the core. Whether you do or not is okay, as we'll be specifying our desired core in just a few seconds anyway.

Once you're done downloading cores (you can come back to this menu and download more cores at any time), close the Updater window and return to the main window, where we'll need to configure some options.

Starting from the top, the Normal ROM path is where you select the ROM you want to play. It will not hide inappropriate files, so make sure you pick the right one for the system you wish to emulate ;)

Next, we need to tell RetroArch where to store and load its settings, via the RetroArch config file path. Click Open, and then navigate to your RetroArch folder and choose the file named retroarch.cfg. Likewise, for RetroArch path, click Open, navigate to the same folder and select retroarch.exe.

Finally, the Emulator core path lets us select which emulation core we wish to use. So, click Open, navigate to the RetroArch folder and look for your desired core that you downloaded from the Updater, such as gambatte-0.5wip1-x86_64.dll in my case. RetroArch can be paired with any emulator core that conforms to the libretro API specification, including but not limited to the original libretro (previously known as libsnes) derived from byuu's bsnes.

At this point, simple emulation should be functional, so go ahead and try it by clicking on the big button labeled Start RetroArch. If it works, congratulations! You're ready to play. Check out the advanced configuration options to learn about filters/shaders, netplay, rewind support and more.

If it doesn't work, click on the File menu at the top of the window and select Show log. This will give you some information on why it failed. If you seek help at the RetroArch forums or in the RetroArch IRC channel, be sure to have this information handy, as it will help others solve your problem.

If you would like to explore some of RetroArch's more advanced features, check out this guide.

For Linux Users

If you're using a Debian-based distro, such as Ubuntu or Mint, you can use my PPA repo, where I package a number of emulators, including RetroArch and all flavors of libretro. To install RetroArch, open Synaptic Package Manager and add ppa:hunter-kaller/ppa to your software sources. You can then install any of the packages through your normal installation procedure of choice.

Otherwise, configuration is just like in Windows, except your retroarch.cfg file is initially installed to /etc/retroarch.cfg (but can then be copied to and overridden by any retroarch.cfg file located in ~/.config/retroarch/) and the emulation cores install to /usr/lib/.