There are several ways to output 15KHz emulation via GroovyMAME and RetroArch without an external downscaler such as CRTEmudriver for Windows and the Linux distro Batocera. These are very solid options to play retro games in their native resolution on a standard definition CRT, but more options are always welcome. Groovy MiSTer by the late developer Psakhis is a project forked from Calamity’s GroovyMAME. Instead of using a PC’s GPU, Groovy MiSTer streams the audio and video over LAN to a MiSTer FPGA which outputs to a 15KHz CRT, and communicates the controls via the MiSTer back to the PC. Whilst the MiSTer FPGA can directly play a wealth of arcade games, there are still many games that are only accessible by emulation.
Groovy MiSTer has been available for over a year now but its difficulty to set up poses as a barrier to entry. Reddit user HeadXT wrote an easy to follow guide and also reached out to the community for help with some areas they could not get working. Neon Dagger answered the call and made an in-depth video guide on setting up Groovy Mister, and even went the extra lengths to test latency which is equivalent, and sometimes faster than the original arcade PCB. If you are looking into setting up Groovy Mister, this is the guide to follow.
Please also check out Lu’s posts for further information as well as using Mister Cast to mirror a PC to a 15KHz CRT via the MiSTer FPGA
Groovy MiSTer: https://www.retrorgb.com/use-a-mister-fpga-to-connect-a-pc-to-a-crt-with-groovy-mister.html
Mister Cast: https://www.retrorgb.com/mirror-your-pc-screen-to-a-crt-with-mistercast.html