Hi

If you right click the lightning bolt you will see some settings that you can change.

By reducing the playback resolution and framerate HD video and complex effects, eg picture in picture, play smoother due to less processing required - this is particularly good on lower spec computers.

You can also reduce processor load during preview playback by turning on proxy files in the projects settings.

Proxy files are for HD video and are lower definition versions of the originals and also require less processing to preview - the only downside is that on long video clips they can take several minutes to create and they do take up more disc space, however when you have finished the project you can delete them - they will be recreated if you need to go back to the project again.

I leave the two settings shown in the image above turned on and use proxy files - they do not affect the final video export or burn to disc and the original files are not altered in any way.

HTH

John EB