15 Replies Latest reply on Nov 18, 2010 10:44 AM by Gary Andrew

    Help:  Constant scalaing speed across several clips.

    Jon-M-Spear Level 4

      Senior moment again, I'm afraid.

       

      I have a sequence containing many single talking heads to camera.  These vary in length from 4 seconds to 30 seconds.

       

      I want to pull into each clip at the same speed. Naturally, because they all vary in length, they will not all end on the same percentage scale-up - so setting the outpoint of each clip to, say, 110% will not work, as a shorter clip will move faster than a longer one..

       

      I have applied scale keyframes so that each clip begins at 100%.  I want to set the outpoint percentage so that each clip scales up at the same speed/velocity.

       

      Without using trial and error (of which there are too many clips to realistically do this), can anyone please tell me how to go about setting the clip scale using speed/velocity as the criteria, not percentage.  I cannot see how to make use of the graph to acheive this.

       

      Thanks in advance.

        • 1. Re: Help:  Constant scalaing speed across several clips.
          dradeke Adobe Employee

          Hey, I'm not sure I have a total idea of what you're trying to do, but two things do come to mind that might help you discover the answer

           

          1. in the wing menu of the effects control panel, you can save your effect as a preset and then be able to apply it to all of your clips.  Then, if you have to tweak, you've at least saved some time in applying the effect and getting it in the ball park.
          2. You do have 'easing' controls inside of Premiere Pro so that you can adjust the speed ramp as it comes to the keyframe.  You might look into the help section on this and see it gives you the answer http://help.adobe.com/en_US/premierepro/cs/using/WS2A48F48C-8A53-4ef4-988A-58A122C2FCC2a.h tml

           

          Cheers,

          Dennis

          • 2. Re: Help:  Indentical pull-in speed across several clips.
            Jon-M-Spear Level 4

            Thanks for your reply.  I admit, my post was rather clumsily written!

             

            I read through that page you attached several times last night, and I don't think it's addressing my issue.  However, it may be staring me in the face.

             

            Let's say that I have a clip of 4 seconds.  I apply a motion (scale) keyframe at the in-point of 100%.  I add a keyframe at the out-point of (say) 110%.  Whether it's linear or bezier is irrelevant...

             

            ...Whatever the speed (rate of change) of that motion turns out to be, I want to make all other clips in the sequence (all different lengths) the same speed.  Naturally, because they are all of differing lengths, their out-point keyframes will not be 110% (unless they are 4 seconds long).

             

            I think that's what I mean ;-(

            • 3. Re: Help:  Indentical pull-in speed across several clips.
              davidbeisner2010 Level 3

              I get what you're asking for, and it seems like it should be something that is easily doable... I've got some ideas, but I need to attend to some work here first, so let me do some playing and see if I can figure something out for you...

              • 4. Re: Help:  Indentical pull-in speed across several clips.
                Jon-M-Spear Level 4

                Thanks, that's greatly appreciated.

                 

                It's probably something that I have done in After Effects time and time again, but I just don't seem to be able to transfer the rationale across!!

                • 5. Re: Help:  Indentical pull-in speed across several clips.
                  davidbeisner2010 Level 3

                  Ok... as I was figuring this out, I'm thinking that maybe you're overthinking the math a little bit. There are two solutions.

                   

                  First, if, as I originally understood your needs, you want to shave the same amount of time off each clip, simply take your first clip, write down the beginning time, take it to 110%, write down the ending time, and figure out how many frames you chopped off. Then simply take your other clips, write down their beginning times, shave off the same number of frames, and you'll get an ending time. Then you can either run a math macro on it in a program like Excel to figure out what the percentage would be, or right click on the clip in the timeline, go to "speed and duration" and there you can manually enter a frame value for what you want the clip to be. (NOTE: if you're doing a math macro on it in Excel, figure your frames as if you had footage that was 100fps, not 30 or 60... Excel doesn't know how to break 30 at 100, if you get my drift).

                   

                  Now, as I was thinking this through, it occured to me, that you might be way overthinking this. A percentage is a measurement of the whole. So if you had subtract 10% from a clip of 10 seconds, you've got a clip at 9 seconds. However, if you've got a clip at 20 seconds and you subtract 10%, you're not subtracting 1, but 2, leaving you with 18 seconds. So the rate at which end up with your clips is the same, when working with percentages. Make sense? So you might just simply need to speed each clip up by the same rate (percentage) and you'll get what you're looking for.

                   

                  Does this help, or have I missed your goal?

                  • 6. Re: Help:  Indentical pull-in speed across several clips.
                    Colin Brougham Level 6

                    I don't know of any automatic way to do this or to calculate the values needed, so you'll have to break out the calculator

                     

                    Basically, you need to use the algebraic formula, distance = rate x time. In this case, distance would actually be ending scale value. Using your above example, here's how to figure this out:

                     

                    You have a 10% scale change over a period of four seconds. Plugging this into the formula, you have 10 = rate x 4. By dividing the distance by time, we can calculate rate: 10 / 4 = 2.5. You can also just cheat, and swivel down your scale property twirly to see the velocity:

                     

                    scale.png

                     

                    So, now we know rate (2.5), and you can apply this to your clip's duration to figure out what the ending scale value would need to be in order to maintain that rate. So, let's say your next clip is 8 seconds...

                     

                    ending scale value = 2.5 x 8 = 20

                     

                    In plain English, this means that for your 8 second clip, starting the scale at 100%, you'd need to increase the scale 20% to maintain a constant rate of 2.5% per second. This means your ending scale value would be 120%; setting this value will display the velocity as 2.5 / second as in the image above.

                     

                    Funny, I got into video to avoid math

                    • 7. Re: Help:  Indentical pull-in speed across several clips.
                      Jon-M-Spear Level 4

                      Thanks David and Colin for your input.

                       

                      David.  I think this time you may have been over thinking it.  I know I wasn't very clear, but thanks for your time on it.

                       

                      Colin is spot on, thank you.  That is precisely what I was trying to calculate (unless that's what you were saying in a different way, David).

                       

                      I know that it stumped me, but is there really no way to input the velocity of each clip (say 2.5/second) without calculating it mathematically?

                      • 8. Re: Help:  Indentical pull-in speed across several clips.
                        davidbeisner2010 Level 3

                        Nope, Colin got it and I swung and missed! Colin got into video to avoid math... I think I got into video cause I suck at math! :-) Glad you've got a solution!

                        • 9. Re: Help:  Indentical pull-in speed across several clips.
                          Colin Brougham Level 6

                          ...but is there really no way to input the velocity of each clip (say 2.5/second) without calculating it mathematically?

                           

                          Not really. Since velocity is the result of a change between two values over time, you need a starting point and a stopping point to calculate it. That's why there is no direct method of entering it into the Premiere interface.

                           

                          That said, you can make it a bit easier on yourself. Drop a keyframe at the point where you want the animation to stop; swivel down the Scale property so you can see the velocity graph. Scrub the value for scale; you won't see "Velocity: X / second" change, but the upper and lower limits for the velocity graph will change in step with the Scale value change. As long as you're using linear interpolation for the temporal values of Scale, those values will match the velocity, so you can use that as a quick gauge to set the correct value for your ending Scale keyframe.

                           

                          Sounds gibberishy, I realize, but try it and you'll see what I mean

                          • 10. Re: Help:  Indentical pull-in speed across several clips.
                            Colin Brougham Level 6

                            Colin got into video to avoid math...

                             

                            And to think: I was going to be an engineer or a geneticist Calculus and I were oil and nitroglycerine...

                            • 11. Re: Help:  Indentical pull-in speed across several clips.
                              Harm Millaard Level 7

                              oil and nitroglycerine...

                               

                              That is the ideal combination for spectacular results...

                              • 12. Re: Help:  Indentical pull-in speed across several clips.
                                Colin Brougham Level 6

                                Harm Millaard wrote:

                                 

                                oil and nitroglycerine...

                                 

                                That is the ideal combination for spectacular results...

                                 

                                Not if you saw my report card...

                                • 13. Re: Help:  Identical pull-in speed across several clips.
                                  Jon-M-Spear Level 4

                                  Hmmmm...

                                   

                                  I see.  It's beginning to make sense.  Thanks again.

                                  • 14. Re: Help:  Identical pull-in speed across several clips.
                                    Colin Brougham Level 6

                                    Yeah, it's a little weird and clunky to do it that way. Honestly, breaking out the calculator is probably a lot faster. Just multiply your clip duration by whatever your desired velocity is, and then add that value to 100%; that's your ending keyframe value.

                                    • 15. Re: Help:  Constant scalaing speed across several clips.
                                      Gary Andrew Level 1

                                      The easiest way to do this would be in After Effects using 3D space and a

                                      moving camera.  No math needed...