exactly. right above the preview box theres a scroll bar that has the setting draft, preview, good, and best. Depending on the camera and files your working with might determine how easily the footage will play back. Also your computer being slow might also affect this. I usually play it in draft or preview because its not that essential to watch it in such high quality before rendering. it's mostly just to give you an idea of what your doing. but anyway, set that to preview or draft, whichever works better for you. if that isnt good enough then pull up task manager, then go to processes, right click, go to where it says priority and set it to high. this is about all you can do man.