5 Replies Latest reply on Aug 28, 2008 9:46 AM by Rothrock

    high fps causes glitching

      I've been tasked with writing an app for a psychology experiment. I'd like to use Flash (for fun to learn the technology) but am running into an issue.

      The experiment involves swapping two or more images very rapidly (as quick as every 10 ms / 100 fps). I tried doing this a couple ways, but basically had the images each on their own frame and looped the playback. It works fine for the most part but every few seconds or so it starts to glitch as if the processor or video card is having trouble keeping up.

      I know this is probably a hardware issue, but was wondering if anyone has any ideas for how I might be able to do this. The app is supposed to be a web app. If it can't be done it can't be done, but I'm open to any suggestions (including other technologies) and I appreciate the help. Thanks!
        • 1. Re: high fps causes glitching
          Walter Elias Level 2
          You answered the question yourself: the processor and/or video card are having trouble keeping up. A higher frame rate doesn't just mean higher speed. You're expecting the computer to process 100 images per second, as opposed to the default frame rate of 12 fps. Note that movies run at 25 fps, and North American television at 30 fps. Do you really need something faster than that? Higher than that rate gives you diminished returns because of computer processor limitations. 100 fps is far beyond the rate of human perception.

          Try it at 30 fps and see if you still have the problem.
          • 2. Re: high fps causes glitching
            Yuba30 Level 1
            Hi Walter,

            Thanks for the response. I think they wanted it faster than movies because movies show small changes from frame to frame whereas they are changing the entire image so its easier for the human eye to detect the change. Either way your response was what I was looking for.

            • 3. Re: high fps causes glitching
              Rothrock Level 5
              Actually 100 fps isn't even close to the rate of human perception. But it is far beyond what most (any?) computers can render Flash at. And that is what is important.

              If all your audience will have top of the line processors with lots of memory then they will probably all be able to render at a decent rate. Most likely around 60 or so, depending upon exactly what you are trying to do.

              But even last year's processors (or the year before) will slow it down. With Flash often "less is more" a lower frame rate like 40 or something will render better that if you try and force it to be at 100.
              • 4. Re: high fps causes glitching
                Walter Elias Level 2
                I've read studies that have proven that humans are unable to perceive changes at faster than 90 fps. I can't find the original article I read, but here's one that cites a study which demonstrates that humans can't perceive flashes at higher than 80 fps:

                Human Visual Persistence

                I assume this is the same sort of thing which Yuba is studying. It will be interesting to learn the result.
                • 5. Re: high fps causes glitching
                  Rothrock Level 5
                  That is an interesting article. I can't cite a specific study. I've seen this:


                  About halfway down there is a reference to a US Air Force study suggesting that pilots were able to identify aircraft in as quick as 1/220 of a second.

                  In any event those are all extremes and the part that we can all agree on is that Flash isn't at 100 fps yet!