Automatically download subtitles in mpv using subliminal.

autosub.lua

-- requires subliminal, version 1.0 or newer
-- default keybinding: b
-- add the following to your input.conf to change the default keybinding:
-- keyname script_binding auto_load_subs
local utils = require 'mp.utils'
function load_sub_fn()
	lang_ids = {"en", "es"}
    subl = "/usr/bin/subliminal" 
	--local path = mp.get_property("working-directory").."/"..mp.get_property("path")
	local pathfile = mp.get_property("path")
	local path, file = utils.split_path(pathfile)
	-- we now use 'which subliminal' to find the path
    t = {}
	t.args = {"which", "subliminal"}
	which = utils.subprocess(t).stdout:gsub("^%s*(.-)%s*$", "%1")
	if string.len(which) > 0 then
		subl = which
	else
		mp.msg.warn("which can't find subliminal!")
	end
	for i in ipairs(lang_ids) do
		info = "Searching "..lang_ids[i].." subtitle for "..path
		mp.msg.info(info)
		mp.osd_message(info)
		t.args = {subl, "download", "-l",lang_ids[i], path}
		res = utils.subprocess(t)
		if res.status == 0 then
			subname = path..mp.get_property("filename/no-ext").."."..lang_ids[i].."."
			mp.msg.info("Subtitle "..lang_ids[i].." download succeeded as "..subname)
			mp.osd_message("Subtitle "..lang_ids[i].." download succeeded as "..subname)
			local files = utils.readdir(path, "files")
			for i = 1, #files do
				mp.msg.info("got file "..files[i].."looking for "..subname.." in "..path)
				if ((string.find(path..files[i], subname, 1, true) == nil) == false) then
					subname = path..files[i]
					mp.msg.info("adding "..subname)
					mp.commandv("sub-add", subname, "auto")
				end
			end
		else
			mp.msg.warn("Subtitle "..lang_ids[i].." download failed")
			mp.osd_message("Subtitle "..lang_ids[i].." download failed")
		end
	end
end

mp.add_key_binding("b", "auto_load_subs", load_sub_fn)