Video loops back to beginning.

[mikej99767633]

I am trying to make an AE 25 sec video.  I import a video and add it to the timeline.  I then add text layers and fool around with the opacity of each layer to fade in/out.  I must have done something because now when I preview it, plays from the beginning but only 8 sec and then it loops back to the beginning.  What did the beginner do now?

[Rick Gerard]

Go to the After Effects product page and run through the Beginner tutorials. Just click on Learn & Support. After Effects is extremely complex and in about 25 years of teaching AE I have never known anyone that had any success at all until they studied the basic principals. 

AE is not an editing app, 25 seconds is an eternity in a comp, most of mine are under seven seconds and only one shot. Some of those 7-second comps have a hundred layers. Preview length depends on system resources, composition settings, and Preview settings. 

[imeilfx]

To add to what Rick said please clarify:
Did you import your video file and made a composition based on that file or you did a composition and then imported your file? 
I'm askin because if you did your composition before - you probably made your composition with last saved length (8 seconds) and not a length of your video. So th check that go to Composition/composition settins and check if lenth of your composition is long enouh to fit your video file. 

If there is everything ok with length of your composition - then probably you have not enough of Ram in your compouter to fit all that data from aE for 25 sec playback. To make it better you can chane preview resolution, you can preview your clip part by part (by shortening Work Area), you can also skip frames - there is lot's what you can do but for that - you need to learn basics.

[adevra]

Go to the beginning of your timeline, press B,

Go to the end of your timeline, press N,

By doing these, you just set a "Work Area"

Now click and de-activate the "loop icon" in the preview tool, it's in the screenshot down below,

Learn the basics of after effects timeline 🙂

Good luck on your journey