audio playback speed - pitch playback modes script

[LaptopDev]

I vibe coded the script below. I am trying to toggle between stable pitch and pitch-shift-with-speed change. So that I can just toggle goofy speed on/off.:

-- Speed control with stable pitch mode
-- Manual toggle switches pitch mode
-- Speed changes respect current mode
-- Integer-step, reversible
-- Keys: [ ] speed, \ toggle mode, BS reset

local STEP       = 0.10
local MIN_STEP   = -9    -- 0.1x
local MAX_STEP   =  90   -- 10.0x

local step = 0
local preserve_pitch = false  -- false = chipmunk, true = pitch preserved

local function clamp_step()
    if step < MIN_STEP then step = MIN_STEP end
    if step > MAX_STEP then step = MAX_STEP end
end

local function apply_audio_chain()
    if preserve_pitch then
        mp.set_property_bool("audio-pitch-correction", true)
        mp.commandv("af", "add", "@rb:rubberband")
    else
        mp.set_property_bool("audio-pitch-correction", false)
        mp.commandv("af", "remove", "@rb")
    end
end

local function apply_speed()
    local speed = 1.0 + step * STEP
    apply_audio_chain()
    mp.set_property_number("speed", speed)
    mp.osd_message(string.format(
        "Speed: %.2fx (%s)",
        speed,
        preserve_pitch and "pitch preserved" or "pitch follows"
    ))
end

-- ---------- META TOGGLE ----------

local function toggle_pitch_mode()
    preserve_pitch = not preserve_pitch
    apply_speed()  -- reapply at current step
end

-- ---------- CONTROLS ----------

local function faster()
    step = step + 1
    clamp_step()
    apply_speed()
end

local function slower()
    step = step - 1
    clamp_step()
    apply_speed()
end

local function reset()
    step = 0
    apply_speed()
end

-- ---------- INIT ----------

mp.register_event("file-loaded", function()
    step = 0
    apply_speed()
end)

-- ---------- KEYS ----------

mp.add_key_binding("[", "speed-slower", slower)
mp.add_key_binding("]", "speed-faster", faster)
mp.add_key_binding("\\", "pitch-toggle", toggle_pitch_mode)
mp.add_key_binding("BS", "speed-reset", reset)

-- ---------- IPC ----------

mp.register_script_message("speed-faster", faster)
mp.register_script_message("speed-slower", slower)
mp.register_script_message("pitch-toggle", toggle_pitch_mode)
mp.register_script_message("speed-reset",  reset)

it almost works but there is some distortion with stable pitch mode maybe someone can tell me how to fix it.

I have this other script which is broken but actually plays stable pitch mode correctly:

-- speed-no-chipmunk.lua 
-- Place in ~/.config/mpv/scripts/ and restart mpv.

---------------------------------------------------------------------------
-- parameters
---------------------------------------------------------------------------
local STEP = 0.10           -- speed increment/decrement amount
local MIN, MAX = 0.10, 10.0 -- absolute speed limits

---------------------------------------------------------------------------
-- state
---------------------------------------------------------------------------
local step           = 0     -- signed integer offset (0 ⇒ 1 × speed)
local preserve_pitch = true  -- start with pitch-lock enabled

---------------------------------------------------------------------------
-- helpers
---------------------------------------------------------------------------
local function clamp(v)            return math.max(MIN, math.min(MAX, v)) end
local function speed()             return clamp(1.0 + step * STEP)        end

local function set_chain(cur_speed)
    if preserve_pitch then
        -- Engage Rubber Band and set inverse pitch ratio to keep pitch stable
        mp.commandv("af", "set", string.format(
            "rubberband=transients=crisp:detector=percussive:"
          .. "formant=preserved:phase=independent:pitch=%.6f",
            1.0 / cur_speed))
    else
        -- Pure resampling (pitch follows speed); remove all filters
        mp.commandv("af", "set", "")
    end
end

local function apply()
    local cur_speed = speed()
    set_chain(cur_speed)
    mp.set_property_number("speed", cur_speed)
    mp.osd_message(string.format("Speed %.2fx | %s",
        cur_speed,
        preserve_pitch and "pitch-locked" or "pitch follows"))
end

---------------------------------------------------------------------------
-- actions
---------------------------------------------------------------------------
local function faster() step = step + 1; apply() end
local function slower() step = step - 1; apply() end
local function toggle() preserve_pitch = not preserve_pitch; apply() end
local function reset()  step, preserve_pitch = 0, true; apply() end

---------------------------------------------------------------------------
-- integration with mpv
---------------------------------------------------------------------------
mp.register_event("file-loaded", reset)

-- key bindings (override mpv defaults where they overlap)
mp.add_key_binding("[",  "rb-slower", slower)
mp.add_key_binding("]",  "rb-faster", faster)
mp.add_key_binding("\\", "rb-toggle", toggle)
mp.add_key_binding("BS", "rb-reset",  reset)

-- IPC hooks (usable via script-message and input-ipc-server)
mp.register_script_message("rb-faster", faster)
mp.register_script_message("rb-slower", slower)
mp.register_script_message("rb-toggle", toggle)
mp.register_script_message("rb-reset",  reset)