5 Replies Latest reply on Oct 16, 2015 8:58 AM by GuessWhatIHaveAQuestion

    Velocity percentage?

    GuessWhatIHaveAQuestion

      Hello, I have a question concerning velocity/slow motion. Is there any way to adjust speed not the classical way via time remapping (key framing specific points of time) but with speed percentage, as in Twixtor? This would make it a lot easier for my purposes.

      I don't need any new frames, I just have a 50fps clip I want to play at exactly 50% speed, then speed up to e.g. 150% again, slow down to 70%, and so on. That's really complicated using time remapping only. I would use Twixtor but since Twixtor is a plugin made to create new frames in between 2 frames for smooth super-slow motion at e.g. 60FPS, the result is pretty warpy because twixtor is trying to create new frames although the original offers enough frames in order to be smooth.

       

      I hope my question is understandable, it's kinda hard to explain.

        • 1. Re: Velocity percentage?
          Mylenium Most Valuable Participant

          Twixtor has a basic "nearest frame/ nearest temporal sample" mode just as well. Otherwise converting percentages is not impossible, but you inevitably run into this problem:

           

          Expression Speed and Frequency Control

           

          You need to accumulate the values to know the "real" current speed and frame to base your percentages on.

           

          Mylenium

          • 2. Re: Velocity percentage?
            Dave LaRonde Level 6

            Well, you don't normally use Twixtor to animate speed changes.  You use it to do frame rate conversions.

            And there isn't a frame rate percentage control -- but that shouldn't stop you from doing the arithmetic to figure out what you need to do with Time Remapping.

            And don't be surprised if the outcome looks kind of funny -- you'll probably invent some pretty funky frame rates doing this.

            • 3. Re: Velocity percentage?
              GuessWhatIHaveAQuestion Level 1

              Well, the "real" time is 50 frames per second, isn't it?

              How do I access that mode? Couldn't find anything about it on google.

              • 4. Re: Velocity percentage?
                Rick Gerard Adobe Community Professional & MVP

                Have you looked at the graph editor. If you reveal the reference graph and edit the value graph you can then hover over the speed graph and see the ratio of seconds / second. If you see 1.0 seconds per second then your footage is playing in real time no matter what the frame rate. Here I'm hovering over the first line segment.

                Screen Shot 2015-10-15 at 9.04.41 PM.png
                If I hover over the third line segment I get 0.5 seconds / second or half speed. One second in real time takes 2 seconds of screen time:

                Screen Shot 2015-10-15 at 9.05.57 PM.png

                The fastest the clip plays is found by hovering over the apex of the speed change. The speed graph shows 4.78 seconds per second so 1 second of real time takes about 1/20 of a second of screen time. It's simple math.

                Screen Shot 2015-10-15 at 9.12.35 PM.png

                So this is how you can use the Graph editor to make speed changes. BTW, the curves were achieved by pressing the G key to bring up the pen tool, then hovering over the keyframes and holding down the Alt/Option key to drag out bezier handles on the value graph. Some folks I know prefer to edit the speed graph, but I find it easier to work with the value graph. Either will work.

                 

                If you want to drive the speed change with an expression controlled by a slider then you can use Dan Ebberts' speed controller expression directly. A slider value of 1 will give you real time, a slider value of .5 will give you one second of real time equal to 2 seconds of screen time or a speed of 50%. To make things easier to edit and see in the graph editor I threw in a multiplier so 100 would give you real time and 50 would be half speed. Kind of turns the slider into a percentage slider. The expression looks like this:

                spd = effect("Speed Control")("Slider");

                n = spd.numKeys;

                if (n > 0 && spd.key(1).time < time){

                  accum = spd.key(1).value*(spd.key(1).time - inPoint);

                  for (i = 2; i <= n; i++){

                    if (spd.key(i).time > time) break;

                    k1 = spd.key(i-1);

                    k2 = spd.key(i);

                    accum += (k1.value + k2.value)*(k2.time - k1.time)/2;

                  }

                  accum += (spd.value + spd.key(i-1).value)*(time - spd.key(i-1).time)/2;

                }else{

                  accum = spd.value*(time - inPoint);

                }

                value + accum*.01

                Here's an animation preset that will add the slider to a layer, enable time remapping and set the speed to real time. Dropbox - Time Remapp Speed Control.ffx

                I would suggest that you save it to your user presets and keep it handy. I use it all the time for time remapping. In many cases it is easier than setting a bunch of keyframes and dragging things around.

                • 5. Re: Velocity percentage?
                  GuessWhatIHaveAQuestion Level 1

                  Thank you so much, that was exactly what I was looking for!