lua extension for vlc to generate thumbnail of the current frame using ffmpeg

vlc-ffmpeg-thumbnail.lua

-- generate thumbnail jpeg of the current selected frame using ffmpeg
-- name convention for minidlna or synology

-- install in  ~/.local/share/vlc/lua/extensions/Thumbnail2.lua

-- tested on linux only

function descriptor()
    return {
        title = "Thumbnail2 generator";
        version = "1.0";
        author = "Alex";
        -- url = "";
        shortdesc = "Thumbnail2 generator";
        description = "Thumbnail2 generator call external program";
    }
end

local hex_to_char = function(x)
    return string.char(tonumber(x, 16))
end

local unescape = function(url)
    return url:gsub("%%(%x%x)", hex_to_char)
end

local escape_shell_arg = function(url)
    return "'"..url:gsub("'", "'\\''").."'"
end

function secondstostring(duration)
    return string.format("%02d:%02d:%02d",
                         math.floor(duration/3600),
                         math.floor(duration/60)%60,
                         math.floor(duration%60))
end

function generate(uri, newuri)
    local input = vlc.object.input()
    if input then
        local play_time = vlc.var.get(input, "time")
        --local play_time = (vlc.var.get(input, "position") * vlc.var.get(input, "length"))

        local play_time_ms = (play_time / 1000) % 1000

        -- if tonumber(vlc.misc.version():match('^[0-9]*')) > 2 then
        -- FIXME for some reason by default one hour is added (eg: 00:05 = 01:05)
        --play_time = (play_time / 1000000) - ((1 * 60 * 60) + 1)
        play_time = play_time / 1000000.

        -- end
        local play_time_string = secondstostring(play_time)..string.format(".%03d", play_time_ms)
        --local play_time_string = os.date("%H:%M:%S", play_time)..string.format(".%03d", play_time_ms)
        --vlc.msg.info("[Thumbnail2] elapsed time "..play_time)
        vlc.msg.info("[Thumbnail2] elapsed time string "..play_time_string)

        cmd = string.format('ffmpeg -y -ss %s -i %s -vframes 1 -q:v 2 -s 640x360 %s', play_time_string, escape_shell_arg(uri), escape_shell_arg(newuri))
        vlc.msg.info("[Thumbnail2] executing: "..cmd)
        assert(os.execute(cmd) == 0, cmd)

        vlc.msg.info("[Thumbnail2] generated: "..newuri)
    else
        vlc.msg.info("[Thumbnail2] no input selected")
    end
end

function click_generate()
    local item = vlc.input.item()
    local uri = item:uri()
    uri = unescape(item:uri())
    -- FIXME perhaps should check if the uri is file:// not assume
    uri = string.gsub(uri, '^file://', '')
    local newuri = uri..'.cover.jpg'

     --uri = string.gsub(uri, '/', '\\')
    vlc.msg.info("[Thumbnail2] item name "..uri)

    generate(uri, newuri)
end

function click_generate2()
    local item = vlc.input.item()
    local uri = item:uri()
    uri = unescape(item:uri())
    -- FIXME perhaps should check if the uri is file:// not assume
    uri = string.gsub(uri, '^file://', '')
    local ext = uri:match("[^.]+$")
    local newuri = uri:sub(0, string.len(uri)-string.len(ext))..'jpg'


     --uri = string.gsub(uri, '/', '\\')
    vlc.msg.info("[Thumbnail2] item name "..uri)

    generate(uri, newuri)
end

function activate()
    vlc.msg.info("[Thumbnail2] activate")
    dlg = vlc.dialog(descriptor().title)
    dlg:add_button("MiniDLNA (.cover.jpg)", click_generate,1,1,1,1)
    dlg:add_button("replace ext .jpg", click_generate2,2,1,1,1)
end

function close()
    vlc.msg.info("[Thumbnail2] close")
    vlc.deactivate()
end

function deactivate()
    vlc.msg.info("[Thumbnail2] deactivate")
end