What can I do with this?

With the new Ultimate 64 firmware (>=1.1c) there is an option to receive video frames & audio over a network connection at 50fps.

You can use this tool to capture those frames into an image, audio or video file.

Changelog v1.22 (09/04/2020):

• ~ Added FQDN support to start U64 stream, so IP & FQDN addresses are now both accepted.
• + video & audio listen port added to settings.
• ~ changed ip/fqdn tester timeout to 500ms.
• + Added NTSC support.
• + PAL/NTSC auto switcher.
• ~ Changed (capture) image size field to zoom factor in the setting window.
• + Added image capture diaglog, option to capture to file, clipboard or both.
• + Added CTRL+C to do a quick capture to clipboard.
• ~ Moved FPS / video mode text to statistics window. Changing title bar will prevent OBS form finding right window.
• + Added filedialog to open PRG or D64 with the stream tool.
• + Drag and Drop PRG & D64 images, Drag and drop on video window to mount & run them.   To only do a mount of a D64 file, drag and drop while holding CTRL pressed
• + Added U64 Reset command
• + Basic keyboard input. The input will be put into the u64 keyboard buffer, not into the matrix buffer.
• So it will work with basic and kernal based prg’s, so it doesn’t work everywhere.
• + Custom colour palette can be defined in the settings window, for the purists.
• + Import and export function to save and share your purist palettes.

Download: U64 Streamer v1.22 (630)

source: u64streamer