I'm trying to produce JPEG thumbnails of movies and gifs. I am scaling them
to a particular size, which requires letter boxing them, and I noticed that
the black letterbox I use isn't always black. It works fine when converting
to other formats.
I assume this has something to do with RBG/YUV or YUV Range conversion, but
I'm not fluent in how FFmpeg handles color conversions and haven't found
too much documentation. Here is an example command line I'm using: