9 Replies Latest reply on Jan 11, 2011 1:14 AM by OsakaWebbie

    How to chop every fifth frame (or even out the motion)

    OsakaWebbie Level 1

      I got a large collection of aerial stock footage real cheap, but most of the clips have a strange problem, and the company acquired the footage from elsewhere, so they can't fix it.  (Apparently I'm the first one to notice the problem.)  Every fifth frame is a repeat of the previous frame, so there are four frames forward, then a stop, then four more frames forward.  On slow-moving footage it isn't very noticable (I can still see it, but regular viewers don't seem to notice), but on faster motion it gives it a jittery look that is distracting.  I would like to remove the redundant frames, and I'm hoping I won't have to do it one frame at a time by hand.  (After the frames are removed, of course, the clips will be 20% shorter, so if needed, I'll then slow the speed down and let AE re-interpolate the motion.)  The question is: Does anyone know of an automated way to remove the unwanted frames?

       

      I have AE CS4 (and Premiere Pro CS3, if that is any help with this), running on Windows XP.

        • 1. Re: How to chop every fifth frame (or even out the motion)
          Mike Tomei

          Could this be a problem with footage settings not matching sequence settings?  Like the footage was 24fps placed into a 30fps sequence, creating the need to duplicate frames?  What are the original footage specs supposed to be, and what are the specs of the sequence you're using them in?

           

          Mike Tomei

          1 person found this helpful
          • 2. Re: How to chop every fifth frame (or even out the motion)
            Mylenium Most Valuable Participant

            I concur with the previous poster. Sounds like some pulldown having been introduced in the wrong way. Try the respective options in the footage interpretation dialog, leaving the frame rate at 30 or 29.97fps, but choosing a pulldown pattern, then place it in a 24fps or 25fps comp. I'm sure it will disappear using one of these combinations. also give some attention to possible field issues.

             

            Mylenium

            • 3. Re: How to chop every fifth frame (or even out the motion)
              OsakaWebbie Level 1

              The clips as I received them are definitely 29.97fps.  I had never heard of pulldown (never worked with film), but I read up on it, and it would appear that you guys are right - the problem footage was probably shot at 24p and converted to 29.97 without doing a 3:2 pulldown to interlace some of the frames.  Interestingly, in GSpot the Fields/s spot is blank - does that mean it's 29.97p?  (Is there even a such thing?)  Anyway, I did a series of frame captures from PPro and looked at them in an image viewer, and I can't see any interlacing "stripes" on any of the images.  The collections have both HD and SD (SD widescreen, unfortunately for me) versions of each clip, but this particular symptom is the same in both.

               

              The Interpret Footage dialog box in AE has several Remove Pulldown choices.  I know all the choices (both regular and "advance") are expecting some interlaced frames, but "WWSWW - 24p advance" seems to work for fixing this footage - hooray!

               

              Now for step two.  I now have a 23.976p comp, but I live in a 59.94i world (everything I do is NTSC SD).  The only thing I know how to do would be to render the 24p comp, import the resulting file back into AE, and then add a 3:2 pulldown and make a 29.97 comp, then and render again and delete the intermediate file.  Is there a way to add the pulldown on the comp rather than just on footage in the Project pane?  That would save me several steps.  In this CreativeCow post, Dave LaRonde appears to explain a good method, but the explanation is missing - he just says, "After Effects has a long standing, surefire method for adding pulldown back into 23.976 files:" and then the post stops at that colon, leaving me wanting more...

               

              Also, comments about 3:2 pulldown, like this on Wikipedia's article on 24p, somewhat concern me: "It can be captured as a standard 60i file and edited like footage from  any other camera, while still retaining its 24p aesthetic."  I don't really want the 24p aesthetic - the rest of my stuff is all shot with my own DV camera, fully interlaced.  I like the smooth video look.  Is this a case of "nothing can be done" (I live in Japan, and there is a commonly used phrase here that translates to that)?  Or is there something "better" than 3:2 pulldown for recreating the smooth look, for people who don't necessarily think the film look is cool?  The Wikipedia article on 24p talked about "Optical Flow" for converting 60i to 24p and extrapolating to smooth out the motion, but there was no mention of a reverse version of that.  If you know of something, let me know.  [But naturally, I know that 3:2 pulldown will look better than what I have now, so I am grateful!]

               

              In some cases I might be able to just let it speed up by 20%, but most of the time the clip would end up too short for where I would use it - in fact, often I have to slow stock footage down even more, because typical stock clips are so darn short.  (I use them in mellow music videos, and often I want a clip to last through a complete phrase of a song plus transitions.)  But even if I am happy with the 20% faster clip, I don't know how to tell AE to label the resulting rendered file as 29.97 so that PPro will use it happily in my projects.  Like I said, this is a whole new area for me - thanks for your help.

              • 4. Re: How to chop every fifth frame (or even out the motion)
                OsakaWebbie Level 1

                I just now answered my first question, having found another thread where Dave LaRonde's instruction was intact.  It's in the Render Settings.  And pulldown definitely improves the motion.  But if there is an optical-flow sort of method that would be even better, I'm all ears.

                 

                And my last question is still outstanding, about how to render it at 80% length with "1 frame = 1 frame".  In Render Settings, if I leave pulldown off and select "Use comp's frame rate", I get a 47.952i clip and PPro adds the dumpy frame back in when I put it in an NTSC project.  If I select "Use this frame rate: 29.97", AE adds the dumpy frame.  I never get a shorter, faster clip.

                • 5. Re: How to chop every fifth frame (or even out the motion)
                  OsakaWebbie Level 1

                  Ack!  I just discovered that other clips I'm trying to use have a similar problem, but every 6th frame instead of every 5th (PAL->NTSC conversion in their history, perhaps?).  The Interpret Footage settings don't help with that (they remove one bad frame, but then remove good ones instead).  Any thoughts?

                  • 6. Re: How to chop every fifth frame (or even out the motion)
                    Mylenium Most Valuable Participant

                    GSpot only reads CoDec meta info, so whether something is truly progressive or interlaced it cannot tell just from reading the tags. If you have read Dave's article, then you should pretty much have all the details. If the issues persist, then it was definitely converted wrongly in some way. You can easily "skip" frames using time remapping with an expression. A quick search turned up this post on creativeCOW. This might solve your problem.

                     

                    Mylenium

                    1 person found this helpful
                    • 7. Re: How to chop every fifth frame (or even out the motion)
                      OsakaWebbie Level 1

                      Sorry I was so long in responding - I was busy cleaning up my clips and getting my project out of here.

                       

                      Thank you, Mylenium!  It might have been a "quick search" for you, but I probably would have never found it - the OP had the exact same problem as one of mine, but he used the word "doubled up" whereas I was calling it "duplicated", "repeated", etc. and searching accordingly.

                       

                      Expressions mostly go right over my head (I don't mind the programming aspect, but the interplay between the different effect parameters is still new to me), and I didn't know Time Remapping would do something like that, but it worked like a charm, for both the 24p and 25p originated footage.  I then applied TimeWarp in the "pixel motion" setting to get the optical flow I was hoping for, avoiding the need for pulldown altogether and allowing me the flexibility of choosing whether to slow the footage at all.  (And in the cases where I needed to slow down the clip even more in PPro, I went ahead and combined that percentage in AE's TimeWarp so that it would only do time adjustments once.)

                       

                      "GSpot only reads CoDec meta info, so whether something is truly  progressive or interlaced it cannot tell just from reading the tags."  Is there a way to tell for sure, then?  I' had been guessing based on three clues: (1) GSpot, (2) I can't see any interlacing stripes even in fast-moving footage, and (3) initial settings in AE's Interpret Footage dialog say "Fields: None".  But I'm not very familiar with Quicktime files, which are what these are - perhaps they act different from AVI's in various ways.

                       

                      One last question for the long term.  Since I am now not using the Interpret Footage settings, it is staying at "Fields: None" - that's fine, since the incoming footage does not seem to be interlaced.  But the comp is apparently also progressive (matching the footage, no doubt) - my clue is that during rendering it just counts by frame rather than saying U and L.  Even though I'm outputting as DV-AVI (please don't start ranting about generation loss - I can't handle tons of uncompressed or minimally compressed files on my machine, especially for the HD clips), which I think is inherently interlaced, the fields are not following the motion - alternating frames are just slightly blurrier.  Is that just par for the course, or is there a way to tell AE to make the comp interlaced, so that TimeWarp will utilize interlacing in creating its motion?

                      • 8. Re: How to chop every fifth frame (or even out the motion)
                        Mylenium Most Valuable Participant

                        Is there a way to tell for sure, then?

                         

                        Not really... Sticking with your "clues" is okay, but even if footage shows interlacing artifacts, it may only show them because they have been wrongly introduced at some point just like in reverse they may have been removed which started your questions. Also just like GSpot, Ae will eitehr read meta info in some file formats or make specific assumptions based on its interpretation rules. So it may think that e.g. 720x576 is interlaced with lower fields for DV PAL, but that, too, must not necessarily reflect the facts. The only way to really see it is when viewing it on a native device, meaning a TV screen via DVD, BluRay or playing the captured files off of your camera, but since modern LCDs also do their own tricks with interpolating fields, sharpening or using 100Hz and beyond, that is also getting more difficult.

                         

                        One last question for the long term.  Since I am now not using the Interpret Footage settings, it is staying at "Fields: None" - that's fine, since the incoming footage does not seem to be interlaced.  But the comp is apparently also progressive (matching the footage, no doubt) - my clue is that during rendering it just counts by frame rather than saying U and L.  Even though I'm outputting as DV-AVI (please don't start ranting about generation loss - I can't handle tons of uncompressed or minimally compressed files on my machine, especially for the HD clips), which I think is inherently interlaced, the fields are not following the motion - alternating frames are just slightly blurrier.  Is that just par for the course, or is there a way to tell AE to make the comp interlaced, so that TimeWarp will utilize interlacing in creating its motion?

                         

                        Put your stuff in a comp with double framerate (59.94/60/50fps) and nest it into a comp with the native frame rate (29.97/30/25fps), then apply Timewarp to the nested comp again. Enable Field rendering on teh render queue. This will force AE to sample the fields and in turn will operate the Timewarp effect, but it may not produce a visualyl different result since there is no actual motion between the 2 fields.

                         

                        Mylenium

                        • 9. Re: How to chop every fifth frame (or even out the motion)
                          OsakaWebbie Level 1

                          Thanks for the info on both questions.  Wow, I didn't realize changing from progressive to interlaced would be that complex.  I'll keep that procedure in mind for when I run into a clip is moving really fast and is particularly annoying in final form, but for most of them I probably won't go through all that, especially since you say it may not make much difference anyway.  At some point I have to say, "Good enough," and go on. :-)  Caio!