In some cases you may notice stuttering preview of a 1920 x 1080 timeline. This has been reproduced with certain ATI video cards, but it is possible that it may occur with other cards as well. First, please ensure that your system meets the recommended specifications for Studio 15. Assuming that your system does meet the recommended specifications, this may be due to an issue that can be solved with these steps:
1. Go to Setup > Video and audio preferences.
2. In the Background Rendering section, select “Use this codec for background rendering”.
3. In the codec selection pull-down, select “MPEG-: best for preview”.
4. Click OK.
The video should now play back properly.