4:4:4

4:4:4 is an expression of chroma subsampling, a practice of encoding images by compressing their color information in order to reduce the overall storage size and bitrate of video files.

If every pixel in the 4x2 grid gets a chroma sample, there's actually no subsampling taking place, a situation represented by 4:4:4 expression.

4:4:4 represents the highest video quality, which effectively has no chroma subsampling. Each pixel is represented and retains its own luma and chroma values.

The best video cameras will have the capability to output 4:4:4 chroma. The same applies to video switches and extenders. These are professional grade tools and they're priced accordingly.