I don't know why it does this, I have a simple video file in HD 60 fps and it's previewing in third quality. I Have 8 gig's of ram, 4 core intel i5 processor and GTX770 GPU. I allocated all 7.9 gb of ram to after effects, enabled and disabled disk cache, I purged all memory, etc. I don't know why it only renders for about 10s in the RAM preview, with my rig I should get at least 30s or so right? 10s is unworkable for me and if I make my project more complicated with more effects, it will render less that 10seconds, sometimes even just a few milliseconds :O. The strange thing is that it worked once, yesterday I was able to do very long RAM previews, I don't know how long but at least for 30 seconds and more! I don't know what went wrong and as far as I know I didn't change anything in the settings. It just stopped working properly.
I'm using adobe after effects cs6
please help me...
From faulty Codecs to flaky drivers e.g. for audio this could be anything. As a test, RAM preview something created entirely in AE and see if that works.