[FFmpeg-user] 4-bit and 2-bit gray pixel format?

[Kyle Parker-Robinson]

While looking through the output of "ffmpeg -pix_fmts", I noticed that
there are formats for two 16-bit grayscales (gray16be/gray16le) and an
8-bit grayscale (gray). There's also a 1-bit grayscale, more accurately
called monochrome (mono).

1) I know that gray16be and gray16le stand for big-endian and little
endian, but I don't know what that means in terms of what I should expect
from using them or what the difference of the output would be between these
two? Can anyone please explain that to me?

2) The project I'm working on requires converting videos to 4-bit and 2-bit
grayscale as well, but these do not appear to be options in ffmpeg. Is
there a way to achieve this another way? If needed, I could contribute to
ffmpeg by developing these new pixel formats. They probably aren't widely
needed pixel formats, but my project is dead in its tracks until I can come
up with a way to make these grayscale videos.