betterchapters.lua

-- betterchapters.lua
-- Loads the next or previous playlist entry if there are no more chapters in the seek direction.
-- To bind in input.conf, use: <keybind> script_binding <keybind name>
-- Keybind names: chapter_next, chapter_prev
-- Recommended to use with autoload.lua

function chapter_seek(direction)
    local chapters = mp.get_property_number("chapters")
    local chapter  = mp.get_property_number("chapter")
    if chapter == nil then chapter = 0 end
    if chapters == nil then chapters = 0 end
    if chapter+direction < 0 then
        mp.command("playlist_prev")
    elseif chapter+direction >= chapters then
        mp.command("playlist_next")
    else
        mp.commandv("osd-msg", "add", "chapter", direction)
    end
end

mp.add_key_binding("PGUP", "chapter_next", function() chapter_seek(1) end)
mp.add_key_binding("PGDWN", "chapter_prev", function() chapter_seek(-1) end)

Any way to make it work for files with no chapters?