thumbfast.lua

-- thumbfast.lua
--
-- High-performance on-the-fly thumbnailer
--
-- Built for easy integration in third-party UIs.

local options = {
    -- Socket path (leave empty for auto)
    socket = "",

    -- Thumbnail path (leave empty for auto)
    thumbnail = "",

    -- Maximum thumbnail size in pixels (scaled down to fit)
    -- Values are scaled when hidpi is enabled
    max_height = 200,
    max_width = 200,

    -- Overlay id
    overlay_id = 42,

    -- Spawn thumbnailer on file load for faster initial thumbnails
    spawn_first = false,

    -- Enable on network playback
    network = false,

    -- Enable on audio playback
    audio = false,

    -- Enable hardware decoding
    hwdec = false,

    -- Windows only: use native Windows API to write to pipe (requires LuaJIT)
    direct_io = false
}

mp.utils = require "mp.utils"
mp.options = require "mp.options"
mp.options.read_options(options, "thumbfast")

local pre_0_30_0 = mp.command_native_async == nil

function subprocess(args, async, callback)
    callback = callback or function() end

    if not pre_0_30_0 then
        if async then
            return mp.command_native_async({name = "subprocess", playback_only = true, args = args}, callback)
        else
            return mp.command_native({name = "subprocess", playback_only = false, capture_stdout = true, args = args})
        end
    else
        if async then
            return mp.utils.subprocess_detached({args = args}, callback)
        else
            return mp.utils.subprocess({args = args})
        end
    end
end

local winapi = {}
if options.direct_io then
    local ffi_loaded, ffi = pcall(require, "ffi")
    if ffi_loaded then
        winapi = {
            ffi = ffi,
            C = ffi.C,
            bit = require("bit"),
            socket_wc = "",

            -- WinAPI constants
            CP_UTF8 = 65001,
            GENERIC_WRITE = 0x40000000,
            OPEN_EXISTING = 3,
            FILE_FLAG_WRITE_THROUGH = 0x80000000,
            FILE_FLAG_NO_BUFFERING = 0x20000000,
            PIPE_NOWAIT = ffi.new("unsigned long[1]", 0x00000001),

            INVALID_HANDLE_VALUE = ffi.cast("void*", -1),

            -- don't care about how many bytes WriteFile wrote, so allocate something to store the result once
            _lpNumberOfBytesWritten = ffi.new("unsigned long[1]"),
        }
        -- cache flags used in run() to avoid bor() call
        winapi._createfile_pipe_flags = winapi.bit.bor(winapi.FILE_FLAG_WRITE_THROUGH, winapi.FILE_FLAG_NO_BUFFERING)

        ffi.cdef[[
            void* __stdcall CreateFileW(const wchar_t *lpFileName, unsigned long dwDesiredAccess, unsigned long dwShareMode, void *lpSecurityAttributes, unsigned long dwCreationDisposition, unsigned long dwFlagsAndAttributes, void *hTemplateFile);
            bool __stdcall WriteFile(void *hFile, const void *lpBuffer, unsigned long nNumberOfBytesToWrite, unsigned long *lpNumberOfBytesWritten, void *lpOverlapped);
            bool __stdcall CloseHandle(void *hObject);
            bool __stdcall SetNamedPipeHandleState(void *hNamedPipe, unsigned long *lpMode, unsigned long *lpMaxCollectionCount, unsigned long *lpCollectDataTimeout);
            int __stdcall MultiByteToWideChar(unsigned int CodePage, unsigned long dwFlags, const char *lpMultiByteStr, int cbMultiByte, wchar_t *lpWideCharStr, int cchWideChar);
        ]]

        winapi.MultiByteToWideChar = function(MultiByteStr)
            if MultiByteStr then
                local utf16_len = winapi.C.MultiByteToWideChar(winapi.CP_UTF8, 0, MultiByteStr, -1, nil, 0)
                if utf16_len > 0 then
                    local utf16_str = winapi.ffi.new("wchar_t[?]", utf16_len)
                    if winapi.C.MultiByteToWideChar(winapi.CP_UTF8, 0, MultiByteStr, -1, utf16_str, utf16_len) > 0 then
                        return utf16_str
                    end
                end
            end
            return ""
        end

    else
        options.direct_io = false
    end
end

local spawned = false
local network = false
local disabled = false
local spawn_waiting = false

local x = nil
local y = nil
local last_x = x
local last_y = y

local last_seek_time = nil

local effective_w = options.max_width
local effective_h = options.max_height
local real_w = nil
local real_h = nil
local last_real_w = nil
local last_real_h = nil

local script_name = nil

local show_thumbnail = false

local filters_reset = {["lavfi-crop"]=true, crop=true}
local filters_runtime = {hflip=true, vflip=true}
local filters_all = filters_runtime
for k,v in pairs(filters_reset) do filters_all[k] = v end

local last_vf_reset = ""
local last_vf_runtime = ""

local last_rotate = 0

local par = ""
local last_par = ""

local last_has_vid = 0
local has_vid = 0

local file_timer = nil
local file_check_period = 1/60
local first_file = false

local function debounce(func, wait)
    func = type(func) == "function" and func or function() end
    wait = type(wait) == "number" and wait / 1000 or 0

    local timer = nil
    local timer_end = function ()
        timer:kill()
        timer = nil
        func()
    end

    return function ()
        if timer then
            timer:kill()
        end
        timer = mp.add_timeout(wait, timer_end)
    end
end

local client_script = [=[
#!/usr/bin/env bash
MPV_IPC_FD=0; MPV_IPC_PATH="%s"
trap "kill 0" EXIT
while [[ $# -ne 0 ]]; do case $1 in --mpv-ipc-fd=*) MPV_IPC_FD=${1/--mpv-ipc-fd=/} ;; esac; shift; done
if echo "print-text thumbfast" >&"$MPV_IPC_FD"; then echo -n > "$MPV_IPC_PATH"; tail -f "$MPV_IPC_PATH" >&"$MPV_IPC_FD" & while read -r -u "$MPV_IPC_FD" 2>/dev/null; do :; done; fi
]=]

local function get_os()
    local raw_os_name = ""

    if jit and jit.os and jit.arch then
        raw_os_name = jit.os
    else
        if package.config:sub(1,1) == "\\" then
            -- Windows
            local env_OS = os.getenv("OS")
            if env_OS then
                raw_os_name = env_OS
            end
        else
            raw_os_name = subprocess({"uname", "-s"}).stdout
        end
    end

    raw_os_name = (raw_os_name):lower()

    local os_patterns = {
        ["windows"] = "Windows",
        ["linux"]   = "Linux",

        ["osx"]     = "Mac",
        ["mac"]     = "Mac",
        ["darwin"]  = "Mac",

        ["^mingw"]  = "Windows",
        ["^cygwin"] = "Windows",

        ["bsd$"]    = "Mac",
        ["sunos"]   = "Mac"
    }

    -- Default to linux
    local str_os_name = "Linux"

    for pattern, name in pairs(os_patterns) do
        if raw_os_name:match(pattern) then
            str_os_name = name
            break
        end
    end

    return str_os_name
end

local os_name = get_os()

if options.socket == "" then
    if os_name == "Windows" then
        options.socket = "thumbfast"
    else
        options.socket = "/tmp/thumbfast"
    end
end

if options.thumbnail == "" then
    if os_name == "Windows" then
        options.thumbnail = os.getenv("TEMP").."\\thumbfast.out"
    else
        options.thumbnail = "/tmp/thumbfast.out"
    end
end

local unique = mp.utils.getpid()

options.socket = options.socket .. unique
options.thumbnail = options.thumbnail .. unique

if options.direct_io then
    if os_name == "Windows" then
        winapi.socket_wc = winapi.MultiByteToWideChar("\\\\.\\pipe\\" .. options.socket)
    end

    if winapi.socket_wc == "" then
        options.direct_io = false
    end
end

local mpv_path = "mpv"

if os_name == "Mac" and unique then
    mpv_path = string.gsub(subprocess({"ps", "-o", "comm=", "-p", tostring(unique)}).stdout, "[\n\r]", "")
    mpv_path = string.gsub(mpv_path, "/mpv%-bundle$", "/mpv")
end

local function vf_string(filters, full)
    local vf = ""
    local vf_table = mp.get_property_native("vf")

    if #vf_table > 0 then
        for i = #vf_table, 1, -1 do
            if filters[vf_table[i].name] then
                local args = ""
                for key, value in pairs(vf_table[i].params) do
                    if args ~= "" then
                        args = args .. ":"
                    end
                    args = args .. key .. "=" .. value
                end
                vf = vf .. vf_table[i].name .. "=" .. args .. ","
            end
        end
    end

    if full then
        vf = vf.."scale=w="..effective_w..":h="..effective_h..par..",pad=w="..effective_w..":h="..effective_h..":x=-1:y=-1,format=bgra"
    end

    return vf
end

local function calc_dimensions()
    local width = mp.get_property_number("video-out-params/dw")
    local height = mp.get_property_number("video-out-params/dh")
    if not width or not height then return end

    local scale = mp.get_property_number("display-hidpi-scale", 1)

    if width / height > options.max_width / options.max_height then
        effective_w = math.floor(options.max_width * scale + 0.5)
        effective_h = math.floor(height / width * effective_w + 0.5)
    else
        effective_h = math.floor(options.max_height * scale + 0.5)
        effective_w = math.floor(width / height * effective_h + 0.5)
    end

    local v_par = mp.get_property_number("video-out-params/par", 1)
    if v_par == 1 then
        par = ":force_original_aspect_ratio=decrease"
    else
        par = ""
    end
end

local info_timer = nil

local function info(w, h)
    local display_w, display_h = w, h
    local rotate = mp.get_property_number("video-params/rotate")

    network = mp.get_property_bool("demuxer-via-network", false)
    local image = mp.get_property_native("current-tracks/video/image", false)
    local albumart = image and mp.get_property_native("current-tracks/video/albumart", false)
    disabled = (w or 0) == 0 or (h or 0) == 0 or
        has_vid == 0 or
        (network and not options.network) or
        (albumart and not options.audio) or
        (image and not albumart)

    if info_timer then
        info_timer:kill()
        info_timer = nil
    elseif has_vid == 0 or (rotate == nil and not disabled) then
        info_timer = mp.add_timeout(0.05, function() info(w, h) end)
    end

    if rotate ~= nil and rotate % 180 == 90 then
        display_w, display_h = h, w
    end

    local json, err = mp.utils.format_json({width=display_w, height=display_h, disabled=disabled, available=true, socket=options.socket, thumbnail=options.thumbnail, overlay_id=options.overlay_id})
    mp.commandv("script-message", "thumbfast-info", json)
end

local function remove_thumbnail_files()
    os.remove(options.thumbnail)
    os.remove(options.thumbnail..".bgra")
end

local function spawn(time)
    if disabled then return end

    local path = mp.get_property("path")
    if path == nil then return end

    local open_filename = mp.get_property("stream-open-filename")
    local ytdl = open_filename and network and path ~= open_filename
    if ytdl then
        path = open_filename
    end

    remove_thumbnail_files()

    local vid = mp.get_property_number("vid")
    has_vid = vid or 0

    local args = {
        mpv_path, path, "--no-config", "--msg-level=all=no", "--idle", "--pause", "--keep-open=always", "--really-quiet", "--no-terminal",
        "--edition="..(mp.get_property_number("edition") or "auto"), "--vid="..(vid or "auto"), "--no-sub", "--no-audio",
        "--start="..time, "--hr-seek=no",
        "--ytdl-format=worst", "--demuxer-readahead-secs=0", "--demuxer-max-bytes=128KiB",
        "--vd-lavc-skiploopfilter=all", "--vd-lavc-software-fallback=1", "--vd-lavc-fast", "--vd-lavc-threads=2", "--hwdec="..(options.hwdec and "auto" or "no"),
        "--vf="..vf_string(filters_all, true),
        "--sws-scaler=fast-bilinear",
        "--video-rotate="..last_rotate,
        "--ovc=rawvideo", "--of=image2", "--ofopts=update=1", "--o="..options.thumbnail
    }

    if not pre_0_30_0 then
        table.insert(args, "--sws-allow-zimg=no")
    end

    if os_name == "Windows" then
        table.insert(args, "--input-ipc-server="..options.socket)
    else
        local client_script_path = options.socket..".run"
        local file = io.open(client_script_path, "w+")
        if file == nil then
            mp.msg.error("client script write failed")
            return
        else
            file:write(string.format(client_script, options.socket))
            file:close()
            subprocess({"chmod", "+x", client_script_path}, true)
            table.insert(args, "--script="..client_script_path)
        end
    end

    spawned = true
    spawn_waiting = true

    subprocess(args, true,
        function(success, result)
            if spawn_waiting and (success == false or result.status ~= 0) then
                mp.msg.error("mpv subprocess create failed")
            end
            spawned = false
        end
    )
end

local function run(command)
    if not spawned then return end

    if options.direct_io then
        local hPipe = winapi.C.CreateFileW(winapi.socket_wc, winapi.GENERIC_WRITE, 0, nil, winapi.OPEN_EXISTING, winapi._createfile_pipe_flags, nil)
        if hPipe ~= winapi.INVALID_HANDLE_VALUE then
            local buf = command .. "\n"
            winapi.C.SetNamedPipeHandleState(hPipe, winapi.PIPE_NOWAIT, nil, nil)
            winapi.C.WriteFile(hPipe, buf, #buf + 1, winapi._lpNumberOfBytesWritten, nil)
            winapi.C.CloseHandle(hPipe)
        end

        return
    end

    local file = nil
    if os_name == "Windows" then
        file = io.open("\\\\.\\pipe\\"..options.socket, "r+")
    else
        file = io.open(options.socket, "r+")
    end
    if file ~= nil then
        file:seek("end")
        file:write(command.."\n")
        file:close()
    end
end

local function draw(w, h, script)
    if not w or not show_thumbnail then return end
    local display_w, display_h = w, h
    if mp.get_property_number("video-params/rotate", 0) % 180 == 90 then
        display_w, display_h = h, w
    end

    if x ~= nil then
        mp.command_native({"overlay-add", options.overlay_id, x, y, options.thumbnail..".bgra", 0, "bgra", display_w, display_h, (4*display_w)})
    elseif script then
        local json, err = mp.utils.format_json({width=display_w, height=display_h, x=x, y=y, socket=options.socket, thumbnail=options.thumbnail, overlay_id=options.overlay_id})
        mp.commandv("script-message-to", script, "thumbfast-render", json)
    end
end

local function real_res(req_w, req_h, filesize)
    local count = filesize / 4
    local diff = (req_w * req_h) - count

    if diff == 0 then
        return req_w, req_h
    else
        local threshold = 5 -- throw out results that change too much
        local long_side, short_side = req_w, req_h
        if req_h > req_w then
            long_side, short_side = req_h, req_w
        end
        for a = short_side, short_side - threshold, -1 do
            if count % a == 0 then
                local b = count / a
                if long_side - b < threshold then
                    if req_h < req_w then return b, a else return a, b end
                end
            end
        end
        return nil
    end
end

local function move_file(from, to)
    if os_name == "Windows" then
        os.remove(to)
    end
    -- move the file because it can get overwritten while overlay-add is reading it, and crash the player
    os.rename(from, to)
end

local function seek(fast)
    if last_seek_time then
        run("async seek " .. last_seek_time .. (fast and " absolute+keyframes" or " absolute+exact"))
    end
end

local seek_period = 3/60
local seek_period_counter = 0
local seek_timer
seek_timer = mp.add_periodic_timer(seek_period, function()
    if seek_period_counter == 0 then
        seek(true)
        seek_period_counter = 1
    else
        if seek_period_counter == 2 then
            seek_timer:kill()
            seek()
        else seek_period_counter = seek_period_counter + 1 end
    end
end)
seek_timer:kill()

local function request_seek()
    if seek_timer:is_enabled() then
        seek_period_counter = 0
    else
        seek_timer:resume()
        seek(true)
        seek_period_counter = 1
    end
end

local function check_new_thumb()
    -- the slave might start writing to the file after checking existance and
    -- validity but before actually moving the file, so move to a temporary
    -- location before validity check to make sure everything stays consistant
    -- and valid thumbnails don't get overwritten by invalid ones
    local tmp = options.thumbnail..".tmp"
    move_file(options.thumbnail, tmp)
    local finfo = mp.utils.file_info(tmp)
    if not finfo then return false end
    spawn_waiting = false
    if first_file then
        request_seek()
        first_file = false
    end
    local w, h = real_res(effective_w, effective_h, finfo.size)
    if w then -- only accept valid thumbnails
        move_file(tmp, options.thumbnail..".bgra")

        real_w, real_h = w, h
        if real_w and (real_w ~= last_real_w or real_h ~= last_real_h) then
            last_real_w, last_real_h = real_w, real_h
            info(real_w, real_h)
        end
        return true
    end
    return false
end

file_timer = mp.add_periodic_timer(file_check_period, function()
    if check_new_thumb() then
        draw(real_w, real_h, script_name)
    end
end)
file_timer:kill()

local function thumb(time, r_x, r_y, script)
    if disabled then return end

    time = tonumber(time)
    if time == nil then return end

    if r_x == "" or r_y == "" then
        x, y = nil, nil
    else
        x, y = math.floor(r_x + 0.5), math.floor(r_y + 0.5)
    end

    script_name = script
    if last_x ~= x or last_y ~= y or not show_thumbnail then
        show_thumbnail = true
        last_x = x
        last_y = y
        draw(real_w, real_h, script)
    end

    if time == last_seek_time then return end
    last_seek_time = time
    if not spawned then spawn(time) end
    request_seek()
    if not file_timer:is_enabled() then file_timer:resume() end
end

local function clear()
    file_timer:kill()
    seek_timer:kill()
    last_seek = 0
    show_thumbnail = false
    last_x = nil
    last_y = nil
    if script_name then return end
    mp.command_native({"overlay-remove", options.overlay_id})
end

local function watch_changes()
    local old_w = effective_w
    local old_h = effective_h

    calc_dimensions()

    local vf_reset = vf_string(filters_reset)
    local rotate = mp.get_property_number("video-rotate", 0)

    local resized = old_w ~= effective_w or
        old_h ~= effective_h or
        last_vf_reset ~= vf_reset or
        (last_rotate % 180) ~= (rotate % 180) or
        par ~= last_par

    if resized then
        last_rotate = rotate
        info(effective_w, effective_h)
    elseif last_has_vid ~= has_vid and has_vid ~= 0 then
        info(effective_w, effective_h)
    end

    if spawned then
        if resized then
            -- mpv doesn't allow us to change output size
            run("quit")
            clear()
            spawned = false
            spawn(last_seek_time or mp.get_property_number("time-pos", 0))
        else
            if rotate ~= last_rotate then
                run("set video-rotate "..rotate)
            end
            local vf_runtime = vf_string(filters_runtime)
            if vf_runtime ~= last_vf_runtime then
                run("vf set "..vf_string(filters_all, true))
                last_vf_runtime = vf_runtime
            end
        end
    else
        last_vf_runtime = vf_string(filters_runtime)
    end

    last_vf_reset = vf_reset
    last_rotate = rotate
    last_par = par
    last_has_vid = has_vid
end

local watch_changes_debounce = debounce(watch_changes, 500)

local function sync_changes(prop, val)
    if val == nil then return end

    if type(val) == "boolean" then
        if prop == "vid" then
            has_vid = 0
            last_has_vid = 0
            info(effective_w, effective_h)
            clear()
            return
        end
        val = val and "yes" or "no"
    end

    if prop == "vid" then
        has_vid = 1
    end

    if not spawned then return end

    run("set "..prop.." "..val)
    watch_changes_debounce()
end

local function file_load()
    clear()
    real_w, real_h = nil, nil
    last_real_w, last_real_h = nil, nil
    last_seek_time = nil
    if info_timer then
        info_timer:kill()
        info_timer = nil
    end

    calc_dimensions()
    info(effective_w, effective_h)
    if disabled then return end

    spawned = false
    if options.spawn_first then
        spawn(mp.get_property_number("time-pos", 0))
        first_file = true
    end
end

local function shutdown()
    run("quit")
    remove_thumbnail_files()
    if os_name ~= "Windows" then
        os.remove(options.socket)
        os.remove(options.socket..".run")
    end
end

mp.observe_property("display-hidpi-scale", "native", watch_changes)
mp.observe_property("video-out-params", "native", watch_changes)
mp.observe_property("vf", "native", watch_changes_debounce)
mp.observe_property("vid", "native", sync_changes)
mp.observe_property("edition", "native", sync_changes)

mp.register_script_message("thumb", thumb)
mp.register_script_message("clear", clear)

mp.register_event("file-loaded", file_load)
mp.register_event("shutdown", shutdown)