mpv/player/lua/ytdl_hook.lua

local utils = require 'mp.utils'
local msg = require 'mp.msg'
local options = require 'mp.options'

local o = {
    exclude = "",
    try_ytdl_first = false,
    use_manifests = false,
    all_formats = false,
    force_all_formats = true,
    thumbnails = "none",
    ytdl_path = "",
}

local ytdl = {
    path = "",
    paths_to_search = {"yt-dlp", "yt-dlp_x86", "youtube-dl"},
    searched = false,
    blacklisted = {}
}

options.read_options(o, nil, function()
    ytdl.blacklisted = {} -- reparse o.exclude next time
    ytdl.searched = false
end)

local chapter_list = {}
local playlist_cookies = {}

local function Set (t)
    local set = {}
    for _, v in pairs(t) do set[v] = true end
    return set
end

-- ?: surrogate (keep in mind that there is no lazy evaluation)
local function iif(cond, if_true, if_false)
    if cond then
        return if_true
    end
    return if_false
end

-- youtube-dl JSON name to mpv tag name
local tag_list = {
    ["uploader"]        = "uploader",
    ["channel_url"]     = "channel_url",
    -- these titles tend to be a bit too long, so hide them on the terminal
    -- (default --display-tags does not include this name)
    ["description"]     = "ytdl_description",
    -- "title" is handled by force-media-title
    -- tags don't work with all_formats=yes
}

local safe_protos = Set {
    "http", "https", "ftp", "ftps",
    "rtmp", "rtmps", "rtmpe", "rtmpt", "rtmpts", "rtmpte",
    "data"
}

-- For some sites, youtube-dl returns the audio codec (?) only in the "ext" field.
local ext_map = {
    ["mp3"]         = "mp3",
    ["opus"]        = "opus",
}

local codec_map = {
    -- src pattern  = mpv codec
    ["vtt"]         = "webvtt",
    ["opus"]        = "opus",
    ["vp9"]         = "vp9",
    ["avc1%..*"]    = "h264",
    ["av01%..*"]    = "av1",
    ["mp4a%..*"]    = "aac",
}

-- Codec name as reported by youtube-dl mapped to mpv internal codec names.
-- Fun fact: mpv will not really use the codec, but will still try to initialize
-- the codec on track selection (just to scrap it), meaning it's only a hint,
-- but one that may make initialization fail. On the other hand, if the codec
-- is valid but completely different from the actual media, nothing bad happens.
local function map_codec_to_mpv(codec)
    if codec == nil then
        return nil
    end
    for k, v in pairs(codec_map) do
        local s, e = codec:find(k)
        if s == 1 and e == #codec then
            return v
        end
    end
    return nil
end

local function platform_is_windows()
    return mp.get_property_native("platform") == "windows"
end

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

-- return true if it was explicitly set on the command line
local function option_was_set(name)
    return mp.get_property_bool("option-info/" ..name.. "/set-from-commandline",
                                false)
end

-- return true if the option was set locally
local function option_was_set_locally(name)
    return mp.get_property_bool("option-info/" ..name.. "/set-locally", false)
end

-- youtube-dl may set special http headers for some sites (user-agent, cookies)
local function set_http_headers(http_headers)
    if not http_headers then
        return
    end
    local headers = {}
    local useragent = http_headers["User-Agent"]
    if useragent and not option_was_set("user-agent") then
        mp.set_property("file-local-options/user-agent", useragent)
    end
    local additional_fields = {"Cookie", "Referer", "X-Forwarded-For"}
    for _, item in pairs(additional_fields) do
        local field_value = http_headers[item]
        if field_value then
            headers[#headers + 1] = item .. ": " .. field_value
        end
    end
    if #headers > 0 and not option_was_set("http-header-fields") then
        mp.set_property_native("file-local-options/http-header-fields", headers)
    end
end

local special_cookie_field_names = Set {
    "expires", "max-age", "domain", "path"
}

-- parse single-line Set-Cookie syntax
local function parse_cookies(cookies_line)
    if not cookies_line then
        return {}
    end
    local cookies = {}
    local cookie = {}
    for stem in cookies_line:gmatch('[^;]+') do
        stem = stem:gsub("^%s*(.-)%s*$", "%1")
        local name, value = stem:match('^(.-)=(.+)$')
        if name and name ~= "" and value then
            local cmp_name = name:lower()
            if special_cookie_field_names[cmp_name] then
                cookie[cmp_name] = value
            else
                if cookie.name and cookie.value then
                    table.insert(cookies, cookie)
                end
                cookie = {
                    name = name,
                    value = value,
                }
            end
        end
    end
    if cookie.name and cookie.value then
        local cookie_key = cookie.domain .. ":" .. cookie.name
        cookies[cookie_key] = cookie
    end
    return cookies
end

-- serialize cookies for avformat
local function serialize_cookies_for_avformat(cookies)
    local result = ''
    for _, cookie in pairs(cookies) do
        local cookie_str = ('%s=%s; '):format(cookie.name, cookie.value:gsub('^"(.+)"$', '%1'))
        for k, v in pairs(cookie) do
            if k ~= "name" and k ~= "value" then
                cookie_str = cookie_str .. ('%s=%s; '):format(k, v)
            end
        end
        result = result .. cookie_str .. '\r\n'
    end
    return result
end

-- set file-local cookies, preserving existing ones
local function set_cookies(cookies)
    if not cookies or cookies == "" then
        return
    end

    local option_key = "file-local-options/stream-lavf-o"
    local stream_opts = mp.get_property_native(option_key, {})
    local existing_cookies = parse_cookies(stream_opts["cookies"])

    local new_cookies = parse_cookies(cookies)
    for cookie_key, cookie in pairs(new_cookies) do
        if not existing_cookies[cookie_key] then
            existing_cookies[cookie_key] = cookie
        end
    end

    stream_opts["cookies"] = serialize_cookies_for_avformat(existing_cookies)
    mp.set_property_native(option_key, stream_opts)
end

local function append_libav_opt(props, name, value)
    if not props then
        props = {}
    end

    if name and value and not props[name] then
        props[name] = value
    end

    return props
end

local function edl_escape(url)
    return "%" .. string.len(url) .. "%" .. url
end

local function url_is_safe(url)
    local proto = type(url) == "string" and url:match("^(%a[%w+.-]*):") or nil
    local safe = proto and safe_protos[proto]
    if not safe then
        msg.error(("Ignoring potentially unsafe url: '%s'"):format(url))
    end
    return safe
end

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 is_blacklisted(url)
    if o.exclude == "" then return false end
    if #ytdl.blacklisted == 0 then
        for match in o.exclude:gmatch('%|?([^|]+)') do
            ytdl.blacklisted[#ytdl.blacklisted + 1] = match
        end
    end
    if #ytdl.blacklisted > 0 then
        url = url:match('https?://(.+)')
        for _, exclude in ipairs(ytdl.blacklisted) do
            if url:match(exclude) then
                msg.verbose('URL matches excluded substring. Skipping.')
                return true
            end
        end
    end
    return false
end

local function parse_yt_playlist(url, json)
    -- return 0-based index to use with --playlist-start

    if not json.extractor or
       (json.extractor ~= "youtube:tab" and
        json.extractor ~= "youtube:playlist") then
        return nil
    end

    local query = url:match("%?.+")
    if not query then return nil end

    local args = {}
    for arg, param in query:gmatch("(%a+)=([^&?]+)") do
        if arg and param then
            args[arg] = param
        end
    end

    local maybe_idx = tonumber(args["index"])

    -- if index matches v param it's probably the requested item
    if maybe_idx and #json.entries >= maybe_idx and
        json.entries[maybe_idx].id == args["v"] then
        msg.debug("index matches requested video")
        return maybe_idx - 1
    end

    -- if there's no index or it doesn't match, look for video
    for i = 1, #json.entries do
        if json.entries[i].id == args["v"] then
            msg.debug("found requested video in index " .. (i - 1))
            return i - 1
        end
    end

    msg.debug("requested video not found in playlist")
    -- if item isn't on the playlist, give up
    return nil
end

local function make_absolute_url(base_url, url)
    if url:find("https?://") == 1 then return url end

    local proto, domain, rest =
        base_url:match("(https?://)([^/]+/)(.*)/?")
    local segs = {}
    rest:gsub("([^/]+)", function(c) table.insert(segs, c) end)
    url:gsub("([^/]+)", function(c) table.insert(segs, c) end)
    local resolved_url = {}
    for _, v in ipairs(segs) do
        if v == ".." then
            table.remove(resolved_url)
        elseif v ~= "." then
            table.insert(resolved_url, v)
        end
    end
    return proto .. domain ..
        table.concat(resolved_url, "/")
end

local function join_url(base_url, fragment)
    local res = ""
    if base_url and fragment.path then
        res = make_absolute_url(base_url, fragment.path)
    elseif fragment.url then
        res = fragment.url
    end
    return res
end

local function edl_track_joined(fragments, protocol, is_live, base)
    if type(fragments) ~= "table" or not fragments[1] then
        msg.debug("No fragments to join into EDL")
        return nil
    end

    local edl = "edl://"
    local offset = 1
    local parts = {}

    if protocol == "http_dash_segments" and not is_live then
        msg.debug("Using dash")
        local args = ""

        -- assume MP4 DASH initialization segment
        if not fragments[1].duration and #fragments > 1 then
            msg.debug("Using init segment")
            args = args .. ",init=" .. edl_escape(join_url(base, fragments[1]))
            offset = 2
        end

        table.insert(parts, "!mp4_dash" .. args)

        -- Check remaining fragments for duration;
        -- if not available in all, give up.
        for i = offset, #fragments do
            if not fragments[i].duration then
                msg.verbose("EDL doesn't support fragments " ..
                         "without duration with MP4 DASH")
                return nil
            end
        end
    end

    for i = offset, #fragments do
        local fragment = fragments[i]
        if not url_is_safe(join_url(base, fragment)) then
            return nil
        end
        table.insert(parts, edl_escape(join_url(base, fragment)))
        if fragment.duration then
            parts[#parts] =
                parts[#parts] .. ",length="..fragment.duration
        end
    end
    return edl .. table.concat(parts, ";") .. ";"
end

local function has_native_dash_demuxer()
    local demuxers = mp.get_property_native("demuxer-lavf-list", {})
    for _, v in ipairs(demuxers) do
        if v == "dash" then
            return true
        end
    end
    return false
end

local function valid_manifest(json)
    local reqfmt = json["requested_formats"] and json["requested_formats"][1] or {}
    if not reqfmt["manifest_url"] and not json["manifest_url"] then
        return false
    end
    local proto = reqfmt["protocol"] or json["protocol"] or ""
    return (proto == "http_dash_segments" and has_native_dash_demuxer()) or
        proto:find("^m3u8")
end

local function as_integer(v, def)
    def = def or 0
    local num = math.floor(tonumber(v) or def)
    if num > -math.huge and num < math.huge then
        return num
    end
    return def
end

local function tags_to_edl(json)
    local tags = {}
    for json_name, mp_name in pairs(tag_list) do
        local v = json[json_name]
        if v then
            tags[#tags + 1] = mp_name .. "=" .. edl_escape(tostring(v))
        end
    end
    if #tags == 0 then
        return nil
    end
    return "!global_tags," .. table.concat(tags, ",")
end

-- Convert a format list from youtube-dl to an EDL URL, or plain URL.
--  json: full json blob by youtube-dl
--  formats: format list by youtube-dl
--  use_all_formats: if=true, then formats is the full format list, and the
--                   function will attempt to return them as delay-loaded tracks
-- See res table initialization in the function for result type.
local function formats_to_edl(json, formats, use_all_formats)
    local res = {
        -- the media URL, which may be EDL
        url = nil,
        -- for use_all_formats=true: whether any muxed formats are present, and
        -- at the same time the separate EDL parts don't have both audio/video
        muxed_needed = false,
    }

    local default_formats = {}
    local requested_formats = json["requested_formats"] or json["requested_downloads"]
    if use_all_formats and requested_formats then
        for _, track in ipairs(requested_formats) do
            local id = track["format_id"]
            if id then
                default_formats[id] = true
            end
        end
    end

    local duration = as_integer(json["duration"])
    local single_url = nil
    local streams = {}

    local tbr_only = true
    for _, track in ipairs(formats) do
        tbr_only = tbr_only and track["tbr"] and
                   (not track["abr"]) and (not track["vbr"])
    end

    local has_requested_video = false
    local has_requested_audio = false
    -- Web players with quality selection always show the highest quality
    -- option at the top. Since tracks are usually listed with the first
    -- track at the top, that should also be the highest quality track.
    -- yt-dlp/youtube-dl sorts it's formats from worst to best.
    -- Iterate in reverse to get best track first.
    for index = #formats, 1, -1 do
        local track = formats[index]
        local edl_track = edl_track_joined(track.fragments,
            track.protocol, json.is_live,
            track.fragment_base_url)
        if not edl_track and not url_is_safe(track.url) then
            msg.error("No safe URL or supported fragmented stream available")
            return nil
        end

        local is_default = default_formats[track["format_id"]]
        local tracks = {}
        -- "none" means it is not a video
        -- nil means it is unknown
        if (o.force_all_formats or track.vcodec) and track.vcodec ~= "none" then
            tracks[#tracks + 1] = {
                media_type = "video",
                codec = map_codec_to_mpv(track.vcodec),
            }
            if is_default then
                has_requested_video = true
            end
        end
        if (o.force_all_formats or track.acodec) and track.acodec ~= "none" then
            tracks[#tracks + 1] = {
                media_type = "audio",
                codec = map_codec_to_mpv(track.acodec) or
                        ext_map[track.ext],
            }
            if is_default then
                has_requested_audio = true
            end
        end

        local url = edl_track or track.url
        local hdr = {"!new_stream", "!no_clip", "!no_chapters"}
        local skip = #tracks == 0
        local params = ""

        if use_all_formats then
            for _, sub in ipairs(tracks) do
                -- A single track that is either audio or video. Delay load it.
                local props = ""
                if sub.media_type == "video" then
                    props = props .. ",w=" .. as_integer(track.width)
                                  .. ",h=" .. as_integer(track.height)
                                  .. ",fps=" .. as_integer(track.fps)
                elseif sub.media_type == "audio" then
                    props = props .. ",samplerate=" .. as_integer(track.asr)
                end
                hdr[#hdr + 1] = "!delay_open,media_type=" .. sub.media_type ..
                    ",codec=" .. (sub.codec or "null") .. props

                -- Add bitrate information etc. for better user selection.
                local byterate = 0
                local rates = {"tbr", "vbr", "abr"}
                if #tracks > 1 then
                    rates = {({video = "vbr", audio = "abr"})[sub.media_type]}
                end
                if tbr_only then
                    rates = {"tbr"}
                end
                for _, f in ipairs(rates) do
                    local br = as_integer(track[f])
                    if br > 0 then
                        byterate = math.floor(br * 1000 / 8)
                        break
                    end
                end
                local title = track.format or track.format_note or ""
                if #tracks > 1 then
                    if #title > 0 then
                        title = title .. " "
                    end
                    title = title .. "muxed-" .. index
                end
                local flags = {}
                if is_default then
                    flags[#flags + 1] = "default"
                end
                hdr[#hdr + 1] = "!track_meta,title=" ..
                    edl_escape(title) .. ",byterate=" .. byterate ..
                    iif(#flags > 0, ",flags=" .. table.concat(flags, "+"), "")
            end

            if duration > 0 then
                params = params .. ",length=" .. duration
            end
        end

        if not skip then
            hdr[#hdr + 1] = edl_escape(url) .. params

            streams[#streams + 1] = table.concat(hdr, ";")
            -- In case there is only 1 of these streams.
            -- Note: assumes it has no important EDL headers
            single_url = url
        end
    end

    local tags = tags_to_edl(json)

    -- Merge all tracks into a single virtual file, but avoid EDL if it's
    -- only a single track without metadata (i.e. redundant).
    if #streams == 1 and single_url and not tags then
        res.url = single_url
    elseif #streams > 0 then
        if tags then
            -- not a stream; just for the sake of concatenating the EDL string
            streams[#streams + 1] = tags
        end
        res.url = "edl://" .. table.concat(streams, ";")
    else
        return nil
    end

    if has_requested_audio ~= has_requested_video then
        local not_req_prop = has_requested_video and "aid" or "vid"
        if mp.get_property(not_req_prop) == "auto" then
            mp.set_property("file-local-options/" .. not_req_prop, "no")
        end
    end

    return res
end

local function add_single_video(json)
    local streamurl = ""
    local format_info = ""
    local max_bitrate = 0
    local requested_formats = json["requested_formats"] or json["requested_downloads"]
    local all_formats = json["formats"]
    local has_requested_formats = requested_formats and #requested_formats > 0
    local http_headers = has_requested_formats
                         and requested_formats[1].http_headers
                         or json.http_headers
    local cookies = has_requested_formats
                    and requested_formats[1].cookies
                    or json.cookies

    if o.use_manifests and valid_manifest(json) then
        -- prefer manifest_url if present
        format_info = "manifest"

        local mpd_url = requested_formats and
            requested_formats[1]["manifest_url"] or json["manifest_url"]
        if not mpd_url then
            msg.error("No manifest URL found in JSON data.")
            return
        elseif not url_is_safe(mpd_url) then
            return
        end

        streamurl = mpd_url

        if requested_formats then
            for _, track in pairs(requested_formats) do
                max_bitrate = (track.tbr and track.tbr > max_bitrate) and
                    track.tbr or max_bitrate
            end
        elseif json.tbr then
            max_bitrate = json.tbr > max_bitrate and json.tbr or max_bitrate
        end
    end

    if streamurl == ""  then
        -- possibly DASH/split tracks
        local res = nil

        -- Not having requested_formats usually hints to HLS master playlist
        -- usage, which we don't want to split off, at least not yet.
        if (all_formats and o.all_formats) and
           (has_requested_formats or o.force_all_formats)
        then
            format_info = "all_formats (separate)"
            res = formats_to_edl(json, all_formats, true)
            -- Note: since we don't delay-load muxed streams, use normal stream
            -- selection if we have to use muxed streams.
            if res and res.muxed_needed then
                res = nil
            end
        end

        if not res and has_requested_formats then
            format_info = "youtube-dl (separate)"
            res = formats_to_edl(json, requested_formats, false)
        end

        if res then
            streamurl = res.url
        end
    end

    if streamurl == "" and json.url then
        format_info = "youtube-dl (single)"
        local edl_track = edl_track_joined(json.fragments, json.protocol,
            json.is_live, json.fragment_base_url)

        if not edl_track and not url_is_safe(json.url) then
            return
        end
        -- normal video or single track
        streamurl = edl_track or json.url
    end

    if streamurl == "" then
        msg.error("No URL found in JSON data.")
        return
    end

    set_http_headers(http_headers)

    msg.verbose("format selection: " .. format_info)
    msg.debug("streamurl: " .. streamurl)

    mp.set_property("stream-open-filename", streamurl:gsub("^data:", "data://", 1))

    if mp.get_property("force-media-title", "") == "" then
        mp.set_property("file-local-options/force-media-title", json.title)
    end

    -- set hls-bitrate for dash track selection
    if max_bitrate > 0 and
        not option_was_set("hls-bitrate") and
        not option_was_set_locally("hls-bitrate") then
        mp.set_property_native('file-local-options/hls-bitrate', max_bitrate*1000)
    end

    -- add subtitles
    if json.requested_subtitles ~= nil then
        local subs = {}
        for lang, info in pairs(json.requested_subtitles) do
            subs[#subs + 1] = {lang = lang or "-", info = info}
        end
        table.sort(subs, function(a, b) return a.lang < b.lang end)
        for _, e in ipairs(subs) do
            local lang, sub_info = e.lang, e.info
            msg.verbose("adding subtitle ["..lang.."]")

            local sub = nil

            if sub_info.data ~= nil then
                sub = "memory://"..sub_info.data
            elseif sub_info.url ~= nil and
                url_is_safe(sub_info.url) then
                sub = sub_info.url
            end

            if sub ~= nil then
                local edl = "edl://!no_clip;!delay_open,media_type=sub"
                local codec = map_codec_to_mpv(sub_info.ext)
                if codec then
                    edl = edl .. ",codec=" .. codec
                end
                edl = edl .. ";" .. edl_escape(sub)
                local title = sub_info.name or sub_info.ext
                mp.commandv("sub-add", edl, "auto", title, lang)
            else
                msg.verbose("No subtitle data/url for ["..lang.."]")
            end
        end
    end

    -- add thumbnails
    if (o.thumbnails == 'all' or o.thumbnails == 'best') and json.thumbnails ~= nil then
        local thumb = nil
        local thumb_height = -1
        local thumb_preference = nil

        for i = #json.thumbnails, 1, -1 do
            local thumb_info = json.thumbnails[i]
            if thumb_info.url ~= nil then
                if o.thumbnails == 'all' then
                    msg.verbose("adding thumbnail")
                    mp.commandv("video-add", thumb_info.url, "auto")
                    thumb_height = 0
                elseif (thumb_preference ~= nil and
                        (thumb_info.preference or -math.huge) > thumb_preference) or
                       (thumb_preference == nil and (thumb_info.height or 0) > thumb_height) then
                    thumb = thumb_info.url
                    thumb_height = thumb_info.height or 0
                    thumb_preference = thumb_info.preference
                end
            end
        end

        if thumb ~= nil then
            msg.verbose("adding thumbnail")
            mp.commandv("video-add", thumb, "auto")
        elseif thumb_height == -1 then
            msg.verbose("No thumbnail url")
        end
    end

    -- add chapters
    if json.chapters then
        msg.debug("Adding pre-parsed chapters")
        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 json.description ~= nil and json.duration ~= nil then
        chapter_list = extract_chapters(json.description, json.duration)
    end

    -- set start time
    if json.start_time or json.section_start and
        not option_was_set("start") and
        not option_was_set_locally("start") then
        local start_time = json.start_time or json.section_start
        msg.debug("Setting start to: " .. start_time .. " secs")
        mp.set_property("file-local-options/start", start_time)
    end

    -- set end time
    if json.end_time or json.section_end and
        not option_was_set("end") and
        not option_was_set_locally("end") then
        local end_time = json.end_time or json.section_end
        msg.debug("Setting end to: " .. end_time .. " secs")
        mp.set_property("file-local-options/end", end_time)
    end

    -- set aspect ratio for anamorphic video
    if json.stretched_ratio ~= nil and
        not option_was_set("video-aspect-override") then
        mp.set_property('file-local-options/video-aspect-override', json.stretched_ratio)
    end

    local stream_opts = mp.get_property_native("file-local-options/stream-lavf-o", {})

    -- for rtmp
    if json.protocol == "rtmp" then
        stream_opts = append_libav_opt(stream_opts,
            "rtmp_tcurl", streamurl)
        stream_opts = append_libav_opt(stream_opts,
            "rtmp_pageurl", json.page_url)
        stream_opts = append_libav_opt(stream_opts,
            "rtmp_playpath", json.play_path)
        stream_opts = append_libav_opt(stream_opts,
            "rtmp_swfverify", json.player_url)
        stream_opts = append_libav_opt(stream_opts,
            "rtmp_swfurl", json.player_url)
        stream_opts = append_libav_opt(stream_opts,
            "rtmp_app", json.app)
    end

    if json.proxy and json.proxy ~= "" then
        stream_opts = append_libav_opt(stream_opts,
            "http_proxy", json.proxy)
    end

    if cookies and cookies ~= "" then
        local existing_cookies = parse_cookies(stream_opts["cookies"])
        local new_cookies = parse_cookies(cookies)
        for cookie_key, cookie in pairs(new_cookies) do
            existing_cookies[cookie_key] = cookie
        end
        stream_opts["cookies"] = serialize_cookies_for_avformat(existing_cookies)
    end

    mp.set_property_native("file-local-options/stream-lavf-o", stream_opts)
end

local function check_version(ytdl_path)
    local command = {
        name = "subprocess",
        capture_stdout = true,
        args = {ytdl_path, "--version"}
    }
    local version_string = mp.command_native(command).stdout
    local year, month, day = string.match(version_string, "(%d+).(%d+).(%d+)")

    -- sanity check
    if tonumber(year) < 2000 or tonumber(month) > 12 or
        tonumber(day) > 31 then
        return
    end
    local version_ts = os.time{year=year, month=month, day=day}
    if os.difftime(os.time(), version_ts) > 60*60*24*90 then
        msg.warn("It appears that your youtube-dl version is severely out of date.")
    end
end

local function run_ytdl_hook(url)
    local start_time = os.clock()

    -- strip ytdl://
    if url:find("ytdl://") == 1 then
        url = url:sub(8)
    end

    local format = mp.get_property("options/ytdl-format")
    local raw_options = mp.get_property_native("options/ytdl-raw-options")
    local allsubs = true
    local proxy = nil
    local use_playlist = false

    local command = {
        ytdl.path, "--no-warnings", "-J", "--flat-playlist",
        "--sub-format", "ass/srt/best"
    }

    -- Checks if video option is "no", change format accordingly,
    -- but only if user didn't explicitly set one
    if mp.get_property("options/vid") == "no" and #format == 0 then
        format = "bestaudio/best"
        msg.verbose("Video disabled. Only using audio")
    end

    if format == "" then
        format = "bestvideo+bestaudio/best"
    end

    if format ~= "ytdl" then
        table.insert(command, "--format")
        table.insert(command, format)
    end

    for param, arg in pairs(raw_options) do
        table.insert(command, "--" .. param)
        if arg ~= "" then
            table.insert(command, arg)
        end
        if (param == "sub-lang" or param == "sub-langs" or param == "srt-lang") and (arg ~= "") then
            allsubs = false
        elseif param == "proxy" and arg ~= "" then
            proxy = arg
        elseif param == "yes-playlist" then
            use_playlist = true
        end
    end

    if allsubs == true then
        table.insert(command, "--all-subs")
    end
    if not use_playlist then
        table.insert(command, "--no-playlist")
    end
    table.insert(command, "--")
    table.insert(command, url)

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

        for _, path in pairs(ytdl.paths_to_search) do
            -- search for youtube-dl in mpv's config dir
            local exesuf = platform_is_windows() and not path:lower():match("%.exe$")
                           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.path = ytdl_cmd
                command[1] = ytdl.path
                result = exec(command)
                break
            else
                msg.verbose("No youtube-dl found with path " .. path .. exesuf ..
                            " in config directories")
                command[1] = path
                result = exec(command)
                if result.error_string == "init" then
                    msg.verbose("youtube-dl with path " .. path ..
                                " not found in PATH or not enough permissions")
                else
                    msg.verbose("Found youtube-dl with path " .. path .. " in PATH")
                    ytdl.path = path
                    break
                end
            end
        end

        ytdl.searched = true
    end

    if result.killed_by_us then
        return
    end

    local json = result.stdout
    local parse_err = nil

    if result.status ~= 0 or json == "" then
        json = nil
    elseif json then
        json, parse_err = utils.parse_json(json)
    end

    if json == nil then
        msg.verbose("status:", result.status)
        msg.verbose("reason:", result.error_string)
        msg.verbose("stdout:", result.stdout)
        msg.verbose("stderr:", result.stderr)

        -- trim our stderr to avoid spurious newlines
        local ytdl_err = result.stderr:gsub("^%s*(.-)%s*$", "%1")
        msg.error(ytdl_err)
        local err = "youtube-dl failed: "
        if result.error_string and result.error_string == "init" then
            err = err .. "not found or not enough permissions"
        elseif parse_err then
            err = err .. "failed to parse JSON data: " .. parse_err
        else
            err = err .. "unexpected error occurred"
        end
        msg.error(err)
        if parse_err or string.find(ytdl_err, "yt%-dl%.org/bug") then
            check_version(ytdl.path)
        end
        return
    end

    msg.verbose("youtube-dl succeeded!")
    msg.debug('ytdl parsing took '..os.clock()-start_time..' seconds')

    json["proxy"] = json["proxy"] or proxy

    -- what did we get?
    if json["direct"] then
        -- direct URL, nothing to do
        msg.verbose("Got direct URL")
        return
    elseif json["_type"] == "playlist" or
           json["_type"] == "multi_video" then
        -- a playlist

        if #json.entries == 0 then
            msg.warn("Got empty playlist, nothing to play.")
            return
        end

        local self_redirecting_url =
            json.entries[1]["_type"] ~= "url_transparent" and
            json.entries[1]["webpage_url"] and
            json.entries[1]["webpage_url"] == json["webpage_url"]


        -- some funky guessing to detect multi-arc videos
        if self_redirecting_url and #json.entries > 1
            and json.entries[1].protocol == "m3u8_native"
            and json.entries[1].url then
            msg.verbose("multi-arc video detected, building EDL")

            local playlist = edl_track_joined(json.entries)

            msg.debug("EDL: " .. playlist)

            if not playlist then
                return
            end

            -- can't change the http headers for each entry, so use the 1st
            set_http_headers(json.entries[1].http_headers)
            set_cookies(json.entries[1].cookies or json.cookies)

            mp.set_property("stream-open-filename", playlist)
            if json.title and mp.get_property("force-media-title", "") == "" then
                mp.set_property("file-local-options/force-media-title",
                    json.title)
            end

            -- there might not be subs for the first segment
            local entry_wsubs = nil
            for i, entry in pairs(json.entries) do
                if entry.requested_subtitles ~= nil then
                    entry_wsubs = i
                    break
                end
            end

            if entry_wsubs ~= nil and
                json.entries[entry_wsubs].duration ~= nil then
                for j, req in pairs(json.entries[entry_wsubs].requested_subtitles) do
                    local subfile = "edl://"
                    for _, entry in pairs(json.entries) do
                        if entry.requested_subtitles ~= nil and
                            entry.requested_subtitles[j] ~= nil and
                            url_is_safe(entry.requested_subtitles[j].url) then
                            subfile = subfile..edl_escape(entry.requested_subtitles[j].url)
                        else
                            subfile = subfile..edl_escape("memory://WEBVTT")
                        end
                        subfile = subfile..",length="..entry.duration..";"
                    end
                    msg.debug(j.." sub EDL: "..subfile)
                    mp.commandv("sub-add", subfile, "auto", req.ext, j)
                end
            end

        elseif self_redirecting_url and #json.entries == 1 then
            msg.verbose("Playlist with single entry detected.")
            add_single_video(json.entries[1])
        else
            local playlist_index = parse_yt_playlist(url, json)
            local playlist = {"#EXTM3U"}
            for _, entry in pairs(json.entries) do
                local site = entry.url
                local title = entry.title

                if title ~= nil then
                    title = string.gsub(title, '%s+', ' ')
                    table.insert(playlist, "#EXTINF:0," .. title)
                end

                --[[ some extractors will still return the full info for
                     all clips in the playlist and the URL will point
                     directly to the file in that case, which we don't
                     want so get the webpage URL instead, which is what
                     we want, but only if we aren't going to trigger an
                     infinite loop
                --]]
                if entry["webpage_url"] and not self_redirecting_url then
                    site = entry["webpage_url"]
                end

                local playlist_url = nil

                -- links without protocol as returned by --flat-playlist
                if not site:find("://") then
                    -- youtube extractor provides only IDs,
                    -- others come prefixed with the extractor name and ":"
                    local prefix = site:find(":") and "ytdl://" or
                        "https://youtu.be/"
                    playlist_url = prefix .. site
                elseif url_is_safe(site) then
                    playlist_url = site
                end

                if playlist_url then
                    table.insert(playlist, playlist_url)
                    -- save the cookies in a table for the playlist hook
                    playlist_cookies[playlist_url] = entry.cookies or json.cookies
                end

            end

            if use_playlist and
                not option_was_set("playlist-start") and playlist_index then
                mp.set_property_number("playlist-start", playlist_index)
            end

            mp.set_property("stream-open-filename", "memory://" .. table.concat(playlist, "\n"))
        end

    else -- probably a video
        add_single_video(json)
    end
    msg.debug('script running time: '..os.clock()-start_time..' seconds')
end

local function on_load_hook(load_fail)
    local url = mp.get_property("stream-open-filename", "")
    local force = url:find("^ytdl://")
    local early = force or o.try_ytdl_first
    if early == load_fail then
        return
    end
    if not force and (not url:find("^https?://") or is_blacklisted(url)) then
        return
    end
    run_ytdl_hook(url)
end

mp.add_hook("on_load", 10, function() on_load_hook(false) end)
mp.add_hook("on_load_fail", 10, function() on_load_hook(true) end)

mp.add_hook("on_load", 20, function ()
    msg.verbose('playlist hook')
    local url = mp.get_property("stream-open-filename", "")
    if playlist_cookies[url] then
        set_cookies(playlist_cookies[url])
    end
end)

mp.add_hook("on_preloaded", 10, function ()
    if next(chapter_list) ~= nil then
        msg.verbose("Setting chapters")

        mp.set_property_native("chapter-list", chapter_list)
        chapter_list = {}
    end
end)