I have a mac pro with 64gb os X yosemite, using AE CC. On my timeline I just have one still photo and the work area is just around the one photo which lasts for 30 seconds. I have only a few keyframed moves on the photo. But for some reason after doing a ram preview, it never shows that AE is previewing the 30 seconds in real time, only sporatically. Not that I should have to but I've lowered the resolution to a quarter...both in the preview window and under the composition window.
What could possibly be the problem?
What size is your composition?
What exact version number of AE?
What size and format and color space is that photo?
What kind of CPU are you running?
What are your memory and multiprocessing settings?
What is your cache setup like? (Is it on an SSD?, etc.)