iPhone 4S sound problem

Hello,

I can hear any phonecall but I can't hear my music, video's from youtube, my own video's and so on.

What I already did:

- Reboot
- Install new software
- ...

If I trie to turn the volume up or down it only shows this:

Image may be NSFW.
Clik here to view.

As you can see, there aren't any "white buttons" ...

Anyone can help?

Thanks in advance