mpv script for changing active screen based on video's aspect ratio

change-screen-by-aspect-ratio.lua

-- change-screen-by-aspect-ratio.lua
-- (c)2023, stt
--
-- mpv script for systems with 2+ monitors in portrait and landscape orientation,
-- when new video starts in fullscreen the active screen is changed based on
-- video's aspect ratio
--
-- NOTE: edit the script with screen numbers based on your screen configuration

function checkAspectRatio()
    local videoParams = mp.get_property_native("video-params")
    -- in case of e.g. lavfi-complex there can be no input video, only output
    if not videoParams then
        videoParams = mp.get_property_native("video-out-params")
    end
    if not videoParams then
        return
    end
    local width = videoParams["w"]
    local height = videoParams["h"]
    local aspectRatio = width / height
    -- mp.msg.warn("aspect", aspectRatio)
    if aspectRatio > 1 then
        -- landscape
        mp.set_property("fs-screen", "0")
    else
        -- portrait
        mp.set_property("fs-screen", "1")
    end
end

function onFileLoaded()
    checkAspectRatio()
end

mp.register_event("file-loaded", onFileLoaded)