5 Replies Latest reply on Apr 24, 2008 10:20 PM by Mylenium

    Ram preview cache overwrites disk cache?

      Hi - I'm new to AE CS3, and am struggling with disk & ram caching:

      1) Even though I have disk caching enabled, it doesn't always kick in when I run out of ram cache (when the green bar starts moving). Now, I understand that disk cache will only be utilised if/when it would be quicker to use that than to render a new frame. However, even when the frame rate is like 7 fps for a 720 * 576 project, it still won't use the disk cache? I would have thought that at that point it would be quicker to just use disk cache (on a 7200 drive)?

      2) related to the above; it does kick in when the fps drops down to something like 2 or 3 fps, and a blue bar starts appearing. However...when I then play it later on (spacebar), it starts overwriting the disk cache (or so it seems) with ram caching...basically re-rendering what had already been stored in the disk cache?

      I'm sure though that I'm missing something obvious. Any help would be appreciated!

      System specs: XP Home edition SP2, 3GB RAM, Intel Dual Core Pentium IV, Radeon X1800 GTO (ATI) graphics card, system drive: 250GB (7200rpm), data drive: 250GB (7200rpm).

      Many thanks, 3dmus
        • 1. Re: Ram preview cache overwrites disk cache?
          Andrew Yoole MVP & Adobe Community Professional
          It's not always possible to understand the logic of Disk Cacheing - it seems to have a mind of its own at times to me.

          But it's important to realize that in order to RAM preview, AE has to load cached material back off disk and into RAM. So you will only ever see green-bar previews when viewing RAM previews. The blue-bar stuff is loaded back into RAM whenever a preview of it is requested. Your system is running in the correct manner.
          • 2. Re: Ram preview cache overwrites disk cache?
            Level 1
            Thanks for the quick reply Andrew. I guess I still have an NLE type of mindset; i.e. in Premiere Pro for instance I just hit enter to render and after that's done it plays back in realtime (no matter if I scrub forward, backward, play the section etc)...until I would make a change of course. I'm guessing then, there's no equivalent workflow in AE? I know that I can put it in the render queue etc, but that just wouldn't be as seamless.

            Thanks again.
            • 3. Re: Ram preview cache overwrites disk cache?
              Andrew Yoole MVP & Adobe Community Professional
              Yep, unlike a NLE, AE won't play directly off disk. It will always pull stuff into RAM, meaning preview times are obviously limited.

              The obvious workarounds are lower preview resolution, lower preview frame rate, or just render a preview from the Render Queue as you mentioned.
              • 4. Re: Ram preview cache overwrites disk cache?
                Level 1
                Thanks for the confirmation Andrew. At least it's another excuse to upgrade my machine!

                • 5. Re: Ram preview cache overwrites disk cache?
                  Mylenium Most Valuable Participant
                  You are misunderstanding the AE disk cache, it's as simple as that. AE's cache works layer oriented, not as a means of buffering the active timeline. It is mostly meant to buffer pre-compositions or heavy effects. Therefore it has little or no value in an unstructured, open timeline as you would in an editing app because it gets constantly invalidated and needs to be rebuilt. A single parameter change or slip/ slide of a layer would do that. Based on that knowledge, the smart thing to do would be to pre-compose whenever you have finalized a section of the timeline. When you never touch that segment again, the pre-comp will be buffered to disk and be available more quickly for any successive previews. The more nested stuff you use, the greater the benefits are in the long run.