How do I reverse my sound volume math for my volume slider?

Question

Hi Stackers, I'm building a video player and am kinda stuck at the volume slider part. It's a YouTube style vertical slider, meaning if the slider is in the top position volume should be 100% and if the slider is dragged to the bottom position sound should be 0. Currently it's doing the opposite of what I want :(

Dragging the slider down will make the sound louder, while dragging up lowers it.

Here is my code below dealing with the volume slider.

// Sound Controller Settings ······························
   soundController = new SoundController();
   soundContrColor = soundController.colorChip;
   soundContrGray  = soundController.grayCover;
   soundContrGray.visible     = false;
   soundController.visible    = true;
   soundController.buttonMode = true;
   soundController.soundSlider.addEventListener(MouseEvent.MOUSE_DOWN, sliderDown);

// SoundController Button Mouse Events ························
   public function sliderDown(event:MouseEvent):void
   {
       soundController.soundSlider.startDrag(false, dragBounds);
       soundController.soundSlider.addEventListener(MouseEvent.MOUSE_MOVE, sliderMove);
       soundController.soundSlider.addEventListener(MouseEvent.MOUSE_UP, sliderUp);
       soundContrGray.visible = true;
   }

   public function sliderMove(event:MouseEvent):void
       {
       soundContrGray.height = soundController.soundSlider.y;
       userVolume = Math.round(((soundContrGray.y * soundContrGray.height) / 10) - 4);
       //userVolume = soundContrGray.height;
       setVolume(userVolume);

       trace("soundController.mouseY = "+soundController.soundSlider.y);
       trace("soundContrColor.height = "+Math.round(soundContrGray.height));
       trace("userVolume             = "+userVolume+"\r");

       event.updateAfterEvent();
       }

    public function sliderUp(event:MouseEvent):void
    {
        lastVolPoint = soundContrGray.height;
        setVolume(userVolume);
        event.updateAfterEvent();

        soundController.soundSlider.stopDrag();
        soundController.soundSlider.removeEventListener(MouseEvent.MOUSE_MOVE, sliderMove);
        soundController.soundSlider.removeEventListener(MouseEvent.MOUSE_UP, sliderUp);
    }

[TRACES] when I drag all the way to the top:

soundController.mouseY = 6
soundContrGray.height  = 6
userVolume             = 0

[TRACES] when I drag all the way down:

soundController.mouseY = 56
soundContrGray.height  = 56
userVolume             = 30

I believe this is where the problem lies:

userVolume = Math.round(((soundContrGray.y * soundContrGray.height) / 10) - 4);

The (-4) is an offset value so when you drag it all the way to turn it off, it's 0 and not 4.
I need to reverse this somehow, so the traces above will swap... going down will make userVolume = 4 and going up will make it 30.

Thanks in advance for anyone that takes a look at this one! :)

Answer 1

Since you are getting 0 when you want 100% volume, and 30 when you want 0 volume... try this

setVolume(100 - (userVolume * 100 / 30));

Substitude 0 in equation:
setVolume(100 - (0 * 100 / 30)) --> simplifies to
setVolume(100);

Substitute 30 in equation:
setVolume(100 - (30 * 100 / 30)); --> simplifies to
setVolume(100 - (3000 / 30)); --> simplifies to
setVolume(100 - 100); --> simplifies to
setVolume(0);

Answer 2

I must be missing something because it can't be this simple, can it?

userVolume = 30-Math.round(((soundContrGray.y * soundContrGray.height) / 10) - 4);

Answer 3

Conceptually what you want to do is to have the sound lower the taller soundContrGray. So you need a max value (or in this case a max height) to compare to current value to. I take it that the 30 is the volume slider background's height. I'll use bg for the background height.

userVolume = (soundContrGray.height / bg.heigth);
userVolume = Math.round((1 - userVolume) * 100);

That'll give a relative volume setting independent of the height's of the actual elements, or where they are on the screen.

Answer 4

userVolume = Math.round(100 * (1 - soundContrGray.height /(soundContrGray.y - 4)))