Precache the next entry in your playlist if it is a network source by downloading it to a temp file ahead of time. Change Line 20 to temp directory. It will delete the directory on exit.

ytdl-preload.lua

----------------------
-- #example ytdl_preload.conf
-- # make sure lines do not have trailing whitespace
-- # ytdl_opt has no sanity check and should be formatted exactly how it would appear in yt-dlp CLI, they are split into a key/value pair on whitespace
-- # at least on Windows, do not escape '\' in temp, just us a single one for each divider

-- #temp=R:\ytdltest
-- #ytdl_opt1=-r 50k
-- #ytdl_opt2=-N 5
-- #ytdl_opt#=etc
----------------------
local nextIndex
local caught = true
-- local pop = false
local ytdl = "yt-dlp"
local utils = require 'mp.utils'

local options = require 'mp.options'
local opts = {
    temp = "R:\\ytdl",
    ytdl_opt1 = "",
    ytdl_opt2 = "",
    ytdl_opt3 = "",
    ytdl_opt4 = "",
    ytdl_opt5 = "",
    ytdl_opt6 = "",
    ytdl_opt7 = "",
    ytdl_opt8 = "",
    ytdl_opt9 = "",
}
options.read_options(opts, "ytdl_preload")
local additionalOpts = {}
for k, v in pairs(opts) do
    if k:find("ytdl_opt%d") and v ~= "" then
        additionalOpts[k] = v
        -- print("entry")
        -- print(k .. v)
    end
end
local cachePath = opts.temp

local chapter_list = {}
local json = ""
local filesToDelete = {}

local function exists(file)
    local ok, err, code = os.rename(file, file)
    if not ok then
        if code == 13 then -- Permission denied, but it exists
            return true
        end
    end
    return ok, err
end
local function useNewLoadfile()
    for _, c in pairs(mp.get_property_native("command-list")) do
        if c["name"] == "loadfile" then
            for _, a in pairs(c["args"]) do
                if a["name"] == "index" then
                    return true
                end
            end
        end
    end
end
--from ytdl_hook
local function time_to_secs(time_string)
    local ret
    local a, b, c = time_string:match("(%d+):(%d%d?):(%d%d)")
    if a ~= nil then
        ret = (a * 3600 + b * 60 + c)
    else
        a, b = time_string:match("(%d%d?):(%d%d)")
        if a ~= nil then
            ret = (a * 60 + b)
        end
    end
    return ret
end
local function extract_chapters(data, video_length)
    local ret = {}
    for line in data:gmatch("[^\r\n]+") do
        local time = time_to_secs(line)
        if time and (time < video_length) then
            table.insert(ret, { time = time, title = line })
        end
    end
    table.sort(ret, function(a, b) return a.time < b.time end)
    return ret
end
local function chapters()
    if json.chapters then
        for i = 1, #json.chapters do
            local chapter = json.chapters[i]
            local title = chapter.title or ""
            if title == "" then
                title = string.format('Chapter %02d', i)
            end
            table.insert(chapter_list, { time = chapter.start_time, title = title })
        end
    elseif not (json.description == nil) and not (json.duration == nil) then
        chapter_list = extract_chapters(json.description, json.duration)
    end
end
--end ytdl_hook
local title = ""
local fVideo = ""
local fAudio = ""
local function load_files(dtitle, destination, audio, wait)
    if wait then
        if exists(destination .. ".mka") then
            print("---wait success: found mka---")
            audio = "audio-file=" .. destination .. '.mka,'
        else
            print("---could not find mka after wait, audio may be missing---")
        end
    end
    -- if audio ~= "" then
    --  table.insert(filesToDelete, destination .. ".mka")
    -- end
    -- table.insert(filesToDelete, destination .. ".mkv")
    dtitle = dtitle:gsub("-" .. ("[%w_-]"):rep(11) .. "$", "")
    dtitle = dtitle:gsub("^" .. ("%d"):rep(10) .. "%-", "")
    if useNewLoadfile() then
        mp.commandv("loadfile", destination .. ".mkv", "append", -1,
            audio .. 'force-media-title="' .. dtitle .. '",demuxer-max-back-bytes=1MiB,demuxer-max-bytes=3MiB,ytdl=no')
    else
        mp.commandv("loadfile", destination .. ".mkv", "append",
            audio .. 'force-media-title="' .. dtitle .. '",demuxer-max-back-bytes=1MiB,demuxer-max-bytes=3MiB,ytdl=no')                                                --,sub-file="..destination..".en.vtt") --in case they are not set up to autoload
    end
    mp.commandv("playlist_move", mp.get_property("playlist-count") - 1, nextIndex)
    mp.commandv("playlist_remove", nextIndex + 1)
    caught = true
    title = ""
    -- pop = true
end

local listenID = ""
local function listener(event)
    if not caught and event.prefix == mp.get_script_name() and string.find(event.text, listenID) then
        local destination = string.match(event.text, "%[download%] Destination: (.+).mkv") or
            string.match(event.text, "%[download%] (.+).mkv has already been downloaded")
        -- if destination then print("---"..cachePath) end;
        if destination and string.find(destination, string.gsub(cachePath, '~/', '')) then
            -- print(listenID)
            mp.unregister_event(listener)
            _, title = utils.split_path(destination)
            local audio = ""
            if fAudio == "" then
                load_files(title, destination, audio, false)
            else
                if exists(destination .. ".mka") then
                    audio = "audio-file=" .. destination .. '.mka,'
                    load_files(title, destination, audio, false)
                else
                    print("---expected mka but could not find it, waiting for 2 seconds---")
                    mp.add_timeout(2, function()
                        load_files(title, destination, audio, true)
                    end)
                end
            end
        end
    end
end

--from ytdl_hook
mp.add_hook("on_preloaded", 10, function()
    if string.find(mp.get_property("path"), cachePath) then
        chapters()
        if next(chapter_list) ~= nil then
            mp.set_property_native("chapter-list", chapter_list)
            chapter_list = {}
            json = ""
        end
    end
end)
--end ytdl_hook
function dump(o)
    if type(o) == 'table' then
        local s = '{ '
        for k, v in pairs(o) do
            if type(k) ~= 'number' then k = '"' .. k .. '"' end
            s = s .. '[' .. k .. '] = ' .. dump(v) .. ','
        end
        return s .. '} '
    else
        return tostring(o)
    end
end

local function addOPTS(old)
    for k, v in pairs(additionalOpts) do
        -- print(k)
        if string.find(v, "%s") then
            for l, w in string.gmatch(v, "([-%w]+) (.+)") do
                table.insert(old, l)
                table.insert(old, w)
            end
        else
            table.insert(old, v)
        end
    end
    -- print(dump(old))
    return old
end

local AudioDownloadHandle = {}
local VideoDownloadHandle = {}
local JsonDownloadHandle = {}
local function download_files(id, success, result, error)
    if result.killed_by_us then
        return
    end
    local jfile = cachePath .. "/" .. id .. ".json"

    local jfileIO = io.open(jfile, "w")
    jfileIO:write(result.stdout)
    jfileIO:close()
    json = utils.parse_json(result.stdout)
    -- print(dump(json))
    if json.requested_downloads[1].requested_formats ~= nil then
        local args = { ytdl, "--no-continue", "-q", "-f", fAudio, "--restrict-filenames", "--no-playlist", "--no-part",
            "-o", cachePath .. "/" .. id .. "-%(title)s-%(id)s.mka", "--load-info-json", jfile }
        args = addOPTS(args)
        AudioDownloadHandle = mp.command_native_async({
            name = "subprocess",
            args = args,
            playback_only = false
        }, function()
        end)
    else
        fAudio = ""
        fVideo = fVideo:gsub("bestvideo", "best")
        fVideo = fVideo:gsub("bv", "best")
    end

    local args = { ytdl, "--no-continue", "-f", fVideo .. '/best', "--restrict-filenames", "--no-playlist",
        "--no-part", "-o", cachePath .. "/" .. id .. "-%(title)s-%(id)s.mkv", "--load-info-json", jfile }
    args = addOPTS(args)
    VideoDownloadHandle = mp.command_native_async({
        name = "subprocess",
        args = args,
        playback_only = false
    }, function()
    end)
end

local function DL()
    local index = tonumber(mp.get_property("playlist-pos"))
    if mp.get_property("playlist/" .. index .. "/filename"):find("/videos$") and mp.get_property("playlist/" .. index + 1 .. "/filename"):find("/shorts$") then
        return
    end
    if tonumber(mp.get_property("playlist-pos-1")) > 0 and mp.get_property("playlist-pos-1") ~= mp.get_property("playlist-count") then
        nextIndex = index + 1
        local nextFile = mp.get_property("playlist/" .. nextIndex .. "/filename")
        if nextFile and caught and nextFile:find("://", 0, false) then
            caught = false
            mp.enable_messages("info")
            mp.register_event("log-message", listener)
            local ytFormat = mp.get_property("ytdl-format")
            fVideo = string.match(ytFormat, '(.+)%+.+//?') or 'bestvideo'
            fAudio = string.match(ytFormat, '.+%+(.+)//?') or 'bestaudio'
            -- print("start"..nextFile)
            listenID = tostring(os.time())
            local args = { ytdl, "--dump-single-json", "--no-simulate", "--skip-download",
                "--restrict-filenames",
                "--no-playlist", "--sub-lang", "en", "--write-sub", "--no-part", "-o",
                cachePath .. "/" .. listenID .. "-%(title)s-%(id)s.%(ext)s", nextFile }
            args = addOPTS(args)
            -- print(dump(args))
            table.insert(filesToDelete, listenID)
            JsonDownloadHandle = mp.command_native_async({
                name = "subprocess",
                args = args,
                capture_stdout = true,
                capture_stderr = true,
                playback_only = false
            }, function(...)
                download_files(listenID, ...)
            end)
        end
    end
end

local function clearCache()
    -- print(pop)

    --if pop == true then
    mp.abort_async_command(AudioDownloadHandle)
    mp.abort_async_command(VideoDownloadHandle)
    mp.abort_async_command(JsonDownloadHandle)
    -- for k, v in pairs(filesToDelete) do
    --  print("remove: " .. v)
    --  os.remove(v)
    -- end
    local ftd = io.open(cachePath .. "/temp.files", "a")
    for k, v in pairs(filesToDelete) do
        ftd:write(v .. "\n")
        if package.config:sub(1, 1) ~= '/' then
            os.execute('del /Q /F "' .. cachePath .. "\\" .. v .. '*"')
        else
            os.execute('rm -f ' .. cachePath .. "/" .. v .. "*")
        end
    end
    ftd:close()
    print('clear')
    mp.command("quit")
    --end
end
mp.add_hook("on_unload", 50, function()
    -- mp.abort_async_command(AudioDownloadHandle)
    -- mp.abort_async_command(VideoDownloadHandle)
    mp.abort_async_command(JsonDownloadHandle)
    mp.unregister_event(listener)
    caught = true
    listenID = "resetYtdlPreloadListener"
    -- print(listenID)
end)

local skipInitial
mp.observe_property("playlist-count", "number", function()
    if skipInitial then
        DL()
    else
        skipInitial = true
    end
end)

--from ytdl_hook
local platform_is_windows = (package.config:sub(1, 1) == "\\")
local o = {
    exclude = "",
    try_ytdl_first = false,
    use_manifests = false,
    all_formats = false,
    force_all_formats = true,
    ytdl_path = "",
}
local paths_to_search = { "yt-dlp", "yt-dlp_x86", "youtube-dl" }
--local options = require 'mp.options'
options.read_options(o, "ytdl_hook")

local separator = platform_is_windows and ";" or ":"
if o.ytdl_path:match("[^" .. separator .. "]") then
    paths_to_search = {}
    for path in o.ytdl_path:gmatch("[^" .. separator .. "]+") do
        table.insert(paths_to_search, path)
    end
end

local function exec(args)
    local ret = mp.command_native({
        name = "subprocess",
        args = args,
        capture_stdout = true,
        capture_stderr = true
    })
    return ret.status, ret.stdout, ret, ret.killed_by_us
end

local msg = require 'mp.msg'
local command = {}
for _, path in pairs(paths_to_search) do
    -- search for youtube-dl in mpv's config dir
    local exesuf = platform_is_windows and ".exe" or ""
    local ytdl_cmd = mp.find_config_file(path .. exesuf)
    if ytdl_cmd then
        msg.verbose("Found youtube-dl at: " .. ytdl_cmd)
        ytdl = ytdl_cmd
        break
    else
        msg.verbose("No youtube-dl found with path " .. path .. exesuf .. " in config directories")
        --search in PATH
        command[1] = path
        es, json, result, aborted = exec(command)
        if result.error_string == "init" then
            msg.verbose("youtube-dl with path " .. path .. exesuf .. " not found in PATH or not enough permissions")
        else
            msg.verbose("Found youtube-dl with path " .. path .. exesuf .. " in PATH")
            ytdl = path
            break
        end
    end
end
--end ytdl_hook

mp.register_event("start-file", DL)
mp.register_event("shutdown", clearCache)
local ftd = io.open(cachePath .. "/temp.files", "r")
while ftd ~= nil do
    local line = ftd:read()
    if line == nil or line == "" then
        ftd:close()
        io.open(cachePath .. "/temp.files", "w"):close()
        break
    end
    -- print("DEL::"..line)
    if package.config:sub(1, 1) ~= '/' then
        os.execute('del /Q /F "' .. cachePath .. "\\" .. line .. '*" >nul 2>nul')
    else
        os.execute('rm -f ' .. cachePath .. "/" .. line .. "* &> /dev/null")
    end
end

@bitingsock

@lamborghinipth ok both fixes are live over on the repo. subLangs is now a script-opt you can set in ytdl-preload.conf for you, something like subLangs=vi,zh.* is what you want

Thanks for quick update.
I have downloaded and tested https://github.com/bitingsock/ytdl-preload

There maybe 3 issues:

1.1 - The video is downloaded but MPV still connect to Youtube link and plays online video instead of playing downloaded file
1.2 - And of course, it also does not delete temp downloaded files after I close MPV window.
1.3 - Further more, the script will run and download video again whenever I click to play in MPV Playlist. As you see, 3 videos ..._I_Built_100_Wells_In_Africa-mwKJfNYwvm8 were downloaded: 2 vids at 720p and 1 at 1080p (I do not understand why we have 2 different qualities here though I didn't change quality of Youtube video, everything is default).

---

2 - Only 2 subLangs can be downloaded at a time. I cannot download the third language or more.
When I set subLangs=en,vi,zh -> the script only downloads EN and VI sub (I did't find ZH sub)
while if I set subLangs=en,vi,zh.*, the script downloads EN sub and all exts of ZH sub (I didn't find VI sub)

---

3 - Downloaded Date
I see all downloaded date are today in previous version of ytdl-preload.lua
The date makes me confuse now in latest version.

Please double check!

1: I have confirmed it working on windows and ubuntu 22.04. Something is wrong with your setup somehow. Please provide an mpv log. That said, it is intentional that the video is downloaded separately for each instance, as someone may have multiple mpv instances open downloading playlists.
2: that video has no native VI subs, only the auto-translated ones, you'll have to learn a little regex to get the exact sub selection you want. If you want auto translated subs you will need to include --write-auto-subs as a ytdl_opts# in ytdl-preload.conf
3: I have no control over the date, that's a yt-dlp issue. I highly doubt it was different in the previous version here, nothing about that part changed.

@bitingsock
Sorry for late response
I have tried your latest version and it work perfectly now.

2: that video has no native VI subs, only the auto-translated ones, you'll have to learn a little regex to get the exact sub selection you want. If you want auto translated subs you will need to include --write-auto-subs as a ytdl_opts# in ytdl-preload.conf

This is my yt-dlp.conf

-o "dl/%(title)s.%(ext)s"
--format=bv+ba/b
--no-check-certificates
--trim-filenames 100
--yes-playlist
--write-sub
--write-auto-sub

This is ytdl-preload.conf - your latest version

#ytdl_preload.conf
# make sure lines do not have trailing whitespace
# ytdl_opt has no sanity check and should be formatted exactly how it would appear in yt-dlp CLI, they are split into a key/value pair on whitespace
# at least on Windows, do not escape '\' in temp, just us a single one for each divider

temp=C:\MPV\dl
subLangs=en,vi
ytdl_opt1=--extractor-args youtube:player_client=android,web
ytdl_opt2=--throttled-rate 1M
ytdl_opt3=-N 5
#ytdl_opt4=

I have --write-auto-sub in yt-dlp.conf so do I need to write this into ytdl-preload.conf?

I would think the yt-dlp.conf should be fine but you probably want your subLangs to be something like:
en,vi,vi-en,zh-[^-]*,zh-.*-en
this should get:

english,
vietnamese (not auto translated),
vietnamese (auto translated from english),
chinese (simplified and traditional, not auto translated),
and
chinese (simplified and traditional, auto translated from english)

respectively

@bitingsock

I would think the yt-dlp.conf should be fine but you probably want your subLangs to be something like: en,vi,vi-en,zh-[^-]*,zh-.*-en this should get:

english, vietnamese (not auto translated), vietnamese (auto translated from english), chinese (simplified and traditional, not auto translated), and chinese (simplified and traditional, auto translated from english)

respectively

Thanks a lot! It works as I hope

Some small questions:
1 - Can I disable line 6 in ytdl-preload.conf temp=C:\MPV\dl (you disabled this by default) and I also see it in line 21 of ytdl-preload.lua?

2 - How to download the first link of playlist?

1: if you have edited line 21 of ytdl-preload.lua, you do not need it in ytdl-preload.conf. However, you probably should use the conf setting so that if you update the lua you don't have to worry about changing line 21 every time
2: I will have to add that feature

1: if you have edited line 21 of ytdl-preload.lua, you do not need it in ytdl-preload.conf. However, you probably should use the conf setting so that if you update the lua you don't have to worry about changing line 21 every time

Got it. I will disable the line 21 in .lua file

2: I will have to add that feature

Yes, I think we should force downloading video whenever the link is pasted to MPV player instead of playing directly from the internet
I am also using ytproxy that make ytdlp download in max speed by opening more connections like the way Internet Download Manager (IDM) does. It takes only few seconds to download 100MB video in 720p/1080p quality.

• don't disable it, it still needs to be there for the option to load into.
• if the video is DASH, that's what -N 5 does, gets 5 segments at a time

@bitingsock Ok, got it.

Thanks for your help. Please notify when you update the feature download the first video instead of from the second video.
I am looking forward ^^