VSE: How to Speed up the Preview of Image Strips? The Issue

Is there any way to speed up the preview of image strips in the video sequence editor? Unfortunately, the preview in the VSE is very choppy and indicates that it runs at only a few frames per second. Even worse, the preview starts to lag compared to the music strip (although “AV-sync” is turned on) which makes it very difficult to cut on beats.

What I’ve tried

At first I thought the slowness would be due to transform effects on the images; I have many images on which I’m applying a Ken Burns Effect. But it’s also slow on plain image strips (with no effects on them).

I have already tried to add proxies to the image strips but that didn’t have any noticeable effect.

Reducing the image resolution might be an option, however, I need the additional pixels for the mentioned zoom effects.

Some more Background

My images are not unusually big, I’d say: just 1–3 MB each with about 7–10 megapixels.

I’ve tested this on both Blender 2.74 and on the latest 2.75a version – each running on Ubuntu 14.04 64bit with 8 GB of RAM. I have an older ATI video card, so I can’t use video acceleration.
You could increase the memory cache (1GB by default) to your available physical memory and increase the number of prefetch frames.

This is done in Menu: File / User Preferences in the System-tab. Ctrl-Alt-U