Sound problem when playing videos with headphones.

I have had a search but can find nothing similar to the problem I am having with my ipad. Has anyone else experienced this ?

I have encoded videos to my ipad and they play ok. When playing through the internal speaker there is no issue but when I play through headphones the sound becomes intermittently choppy. It is fine for a few second then makes a blip noise or chops slightly, it is very annoying. This only seems to occur on videos, music is fine on headphones as is youtube, etc. I am baffled, I have even tried different headphones just in case but the problem persists.

Any ideas anyone has would be gratefully received.