CorePNG is a lossless video codec that is based on the Portable Network Graphics lossless bitmap image format that is widely used on the Internet. PNG files are considered to be very high in quality (although there is a constant debate about the merits of PNG versus the merits of the JPEG image format, which is used more widely than PNG on the Internet.
Basically, CorePNG makes a video stream that consists of PNG images. CorePNG has the ability to write P frames and to autodetect when it should. The P frame takes the difference of the previous frame and the current frame and encodes that as a PNG. It supports the RGB color-space at 24- or 32-bit depth. Some of CorePNG's features have been marked as unstable however.
CorePNG was originally developed for use with subtitles, but evolved into a lossless codec that claims sometimes to outdo Huffyuv and Loco in terms of compression.