Unfortunately, VideoIO.jl is only capable of video input, not output (at least as of the last time I checked). See: https://github.com/JuliaIO/VideoIO.jl/issues/36
The most versatile option is, as Tamas mentioned, calling an external program, which is the approach taken by https://github.com/yakir12/FFmpegPipe.jl. If you need more control, you can build your own ffmpeg command pipe as I did here.
2 Likes