-- This script adds control to the dynamic range compression ffmpeg-- filter including key bindings for adjusting parameters.---- See https://ffmpeg.org/ffmpeg-filters.html#acompressor for explanation-- of the parameters. local mp = require 'mp'local options = require 'mp.options' local o = {    default_enable = false,    show_osd = true,    osd_timeout = 4000,    filter_label = mp.get_script_name(),     key_toggle = 'n',    key_increase_threshold = 'F1',    key_decrease_threshold = 'Shift+F1',    key_increase_ratio = 'F2',    key_decrease_ratio = 'Shift+F2',    key_increase_knee = 'F3',    key_decrease_knee = 'Shift+F3',    key_increase_makeup = 'F4',    key_decrease_makeup = 'Shift+F4',    key_increase_attack = 'F5',    key_decrease_attack = 'Shift+F5',    key_increase_release = 'F6',    key_decrease_release = 'Shift+F6',     default_threshold = -25.0,    default_ratio = 3.0,    default_knee = 2.0,    default_makeup = 8.0,    default_attack = 20.0,    default_release = 250.0,     step_threshold = -2.5,    step_ratio = 1.0,    step_knee = 1.0,    step_makeup = 1.0,    step_attack = 10.0,    step_release = 10.0,}options.read_options(o) local params = {    { name = 'attack',    min=0.01, max=2000, hide_default=true,  dB=''   },    { name = 'release',   min=0.01, max=9000, hide_default=true,  dB=''   },    { name = 'threshold', min= -30, max=   0, hide_default=false, dB='dB' },    { name = 'ratio',     min=   1, max=  20, hide_default=false, dB=''   },    { name = 'knee',      min=   1, max=  10, hide_default=true,  dB='dB' },    { name = 'makeup',    min=   0, max=  24, hide_default=false, dB='dB' },} local function parse_value(value)    -- Using nil here because tonumber differs between lua 5.1 and 5.2 when    -- parsing fractions in combination with explicit base argument set to 10.    -- And we can't omit it because gsub returns 2 values which would get    -- unpacked and cause more problems. Gotta love scripting languages.    return tonumber(value:gsub('dB$', ''), nil)end local function format_value(value, dB)    return string.format('%g%s', value, dB)end local function show_osd(filter)    if not o.show_osd then        return    end     if not filter.enabled then        mp.commandv('show-text', 'Dynamic range compressor: disabled', o.osd_timeout)        return    end     local pretty = {}    for _,param in ipairs(params) do        local value = parse_value(filter.params[param.name])        if not (param.hide_default and value == o['default_' .. param.name]) then            pretty[#pretty+1] = string.format('%s: %g%s', param.name:gsub("^%l", string.upper),                                              value, param.dB)        end    end     if #pretty == 0 then        pretty = ''    else        pretty = '\n(' .. table.concat(pretty, ', ') .. ')'    end     mp.commandv('show-text', 'Dynamic range compressor: enabled' .. pretty, o.osd_timeout)end local function get_filter()    local af = mp.get_property_native('af', {})     for i = 1, #af do        if af[i].label == o.filter_label then            return af, i        end    end     af[#af+1] = {        name = 'acompressor',        label = o.filter_label,        enabled = false,        params = {},    }     for _,param in pairs(params) do        af[#af].params[param.name] = format_value(o['default_' .. param.name], param.dB)    end     return af, #afend local function toggle_acompressor()    local af, i = get_filter()    af[i].enabled = not af[i].enabled    mp.set_property_native('af', af)    show_osd(af[i])end local function update_param(name, increment)    for _,param in pairs(params) do        if param.name == string.lower(name) then            local af, i = get_filter()            local value = parse_value(af[i].params[param.name])            value = math.max(param.min, math.min(value + increment, param.max))            af[i].params[param.name] = format_value(value, param.dB)            af[i].enabled = true            mp.set_property_native('af', af)            show_osd(af[i])            return        end    end     mp.msg.error('Unknown parameter "' .. name .. '"')end mp.add_key_binding(o.key_toggle, "toggle-acompressor", toggle_acompressor)mp.register_script_message('update-param', update_param) for _,param in pairs(params) do    for direction,step in pairs({increase=1, decrease=-1}) do        mp.add_key_binding(o['key_' .. direction .. '_' .. param.name],                           'acompressor-' .. direction .. '-' .. param.name,                           function() update_param(param.name, step*o['step_' .. param.name]); end,                           { repeatable = true })    endend if o.default_enable then    local af, i = get_filter()    af[i].enabled = true    mp.set_property_native('af', af)end