14 Replies Latest reply on Nov 1, 2011 4:28 AM by reindeer4

    Wobbly edges after keying greenscreen footage

    reindeer4 Level 1

      Using a digital camcorder, I recorded myself against a Greenscreen, but I keep ending up with wobbly, shifting edges after keying things out.

      Any suggestions on how to avoid this problem?  (I've tried applying choker and shrinking the size and softening the edge from within keylight - but I've yet to find something that gets things looking right)

       

      I've posted a brief snippet from the video at http://drupal.yourgods.com/greenscreentest

       

      (I added a yellow solid in the background to make the edge problem stand out)

       

      Thanks for any suggestions.

        • 1. Re: Wobbly edges after keying greenscreen footage
          Todd_Kopriva Level 8

          That looks like the result of using extremely poor source footage for color keying work. The compression used in low-end camcorders (especially DV compression) throws away tremendous amounts of exactly the information that color-keying software needs to work.

           

          See this section of After Effects Help for more information:

          "Shooting and acquiring footage for keying"

           

          The section just beneath that ("Tips for keying...") has suggestions for making the best of such footage---especially the tips about selectively blurring a channel before keying to somewhat reduce the noise and artifacts.

          • 2. Re: Wobbly edges after keying greenscreen footage
            reindeer4 Level 1

            Well . . . not sure that's what I was hoping to hear, but thanks for the links which I'm currently reading through.

             

            I have a few more questions below - some of which you may be able to point me in the right direction for, other which may be too camera specific.

             

            1) I have a JVC Everio Digital Camcorder with a built in 80GB hard drive.  Is that one of those low-endish ones you were talking about? 

            (I think it was roughly $300-$400 when we got it about a year ago).

             

            2) The JVC Everio records to its own video format .MOD and when the bundled converter changes those to .WMV format, I saw the file size for a 1:35 second clip go from 108MB down to 33MB.  Do you have any recommendations about how to convert from the proprietary .MOD format to an uncompressed format that After Effects CS4 can handle?  (I think I'd tried the simple 'renaming' method, where you just change the extension to .MPEG or .MPEG-2 but that didn't work for me).

             

            3) The recording size is listed as 740 x 480 px for the camcorder, but on conversion to WMV, the options are to convert to 1280x720, 640x360, or 320x180 - I'd done the largest size as I thought that was best quality, but would I be better off going to 640 x 360?  (In going from the native size up to a larger one for WMV, I don't know if that's interpolating to add pixels and thereby introducing another problem ?)

             

            4) The articles also talk about 4:4:4 being better than 4:2:2 which is in turn preferable to 4:2:0 or 4:1:1.

            How can I find out what my camcorder is shooting?

             

            5) Is there any way to record directly to my computer (via firewire or USB2) to keep things from going through the compression necessary to squeeze it onto the camera's relatively small drive?

             

            Thanks for any help /insights you can provide.

            • 3. Re: Wobbly edges after keying greenscreen footage
              bogiesan Level 4

              You're asking a bunch of questions about elementary, beginning video production. This is a forum devoted to using After Effects, not learning the craft of video shooting. You're will be better served by searching the net for references to your particular camera and for instruction on how to do simple green screen work. We can help you use the chromakeying filters in Afrter Effects but we really can't help you learn how to use a specific consumer camera or how to light for and decompress your acquisition codec, or how to understand chroma sampling ratios.

               

              To do successful green screen work is not particularly complicated but it is an exacting science requiring minimum digital signal integrity and minimum chroma resolution to do well. Generally, highly compressed codecs do no unpack well enough to do good green screen mattes without the finest green screen material and lighting and then, in post, severe processing.

               

              bogiesan

              • 4. Re: Wobbly edges after keying greenscreen footage
                Dave LaRonde Level 6

                I did a quick look-see on that camera, and it has an HDMI connection on it.  You could connect it to something like an AJA I/O box to get higher-quality recordings.  The problem: an AJA box like that costs 10 times more than the camcorder.

                 

                Consumer cameras are great to use for pictures of family and friends, but they generally stink for effects work.

                • 5. Re: Wobbly edges after keying greenscreen footage
                  reindeer4 Level 1

                  bogiesan - this is one of many forums on the Adobe site devoted to helping people get the most out of their Adobe products.  If you're facile with a given product and knowledgeable in a related field (such as someone who uses After Effects and knows a good deal about video cameras) and you feel like pitching in, that's great.  If you lack that knowledge or don't have any interest in helping, however, there's really no need to invest your response with a troll-like tone . . . unless you're just trying to get a rise out of people.

                           

                   

                  Dave - Thanks for the help.  I don't think my specific model (JVC Everio  GZ MG750-BU) has that HDMI connection - just a mini-USB and an AV connection (no Firewire either).  I'll try talking to Everio's tech support again today, but the last technician I spoke too wasn't especially well versed in details like Pixel Aspect Ratios or conversion of MOD files, which is why I thought I'd come to these forums to see if I could figure out what was going wrong with my greenscreened video.

                  • 6. Re: Wobbly edges after keying greenscreen footage
                    Dave LaRonde Level 6

                    No HDMI?  Then you're stuck with what you've got.  Short of buying a new camera, your only other option is to work on improving your lighting for chroma key.  As Bogesian says, there are resources for it on the web only a google away.

                     

                    However, there are no guarantees with consumer cameras.

                    1 person found this helpful
                    • 7. Re: Wobbly edges after keying greenscreen footage
                      reindeer4 Level 1

                      Oh well . . . guess I'll know better for the next camera purchase, and for now, I'll read a bit more about proper lighting and try to come up with some inventive ways to do what I can with what I've got.  Thanks for the help

                      • 8. Re: Wobbly edges after keying greenscreen footage
                        bogiesan Level 4

                        > bogiesan - this is one of many forums on the Adobe site devoted to helping people get the most out of their Adobe products.  If you're facile with a given product and knowledgeable in a related field (such as someone who uses After Effects and knows a good deal about video cameras) and you feel like pitching in, that's great.  If you lack that knowledge or don't have any interest in helping, however, there's really no need to invest your response with a troll-like tone . . . unless you're just trying to get a rise out of people.

                         

                        My god, you are so correct.

                        How stupid of me not to have seen it, twnety years of psychotherapy and you nail my problem in thirty seconds. .

                        But I did give you plenty of useful advice about how to research your camera, how to locate definitions for chroma sampling and how to figure out what your'e doing wrong withyoru equipment. I am more than facile with the product After Effects, major power user. Which is what allows me to warn you asking us to tell you how to get something useful from a consumer camera is only going to be a frsutrating experience for you. I will tell you it canot be done. You will not believe me.

                         

                        So you're saying LaRonde offered up something useful? Way to go, Dave! No, wait, he told you he looked up the camera and found the online descritpion points you to use the HDMI connector but you're saying there really is no HDMI connector? Now how is erroneous advice any better than honest advice to do your research in a more appropriate forum? It's liek looking for help with a physics paper in your auto shop manual. There's pysics in there, for certian, but it's difficult to extract. 

                         

                        In fact, you've ended up exactly where you would have if you'd just listened to me in the first place.

                         

                        There is a report abuse button you can use, Todd gets lots of those.  

                        • 9. Re: Wobbly edges after keying greenscreen footage
                          Todd_Kopriva Level 8

                          Rotoscoping can be tedious (to say the least), but it can also save a shot like this. You may even be able to get good enough results with Roto Brush---which was designed with temporal coherence in mind, so the "boiling" of edges from low-quality, noisy footage won't occur.

                          • 10. Re: Wobbly edges after keying greenscreen footage
                            Todd_Kopriva Level 8

                            BTW, I'll delete any posts after this that contain what appears to be an ad hominem attack. I'm not referring to any one individual; this is a blanket statement.

                            • 11. Re: Wobbly edges after keying greenscreen footage
                              reindeer4 Level 1

                              Todd - thanks for the suggestions on how I might salvage my footage.  My After Effects is only version CS4, not CS5, so don't have access to the RotoBrush tool without downloading a trial version.  I'll take a look at Rotobrushing, though, and see if there's a way to get things looking better without taking too much time. 

                               

                              As for tone, I'll hold off from making any direct response to the snarkiness above and simply do what the poster suggested - click on the abuse button so you or one of the other folks at Adobe can take a more careful look at the thread and see if bogiesan is helping to create the type of atmosphere you want here on the forums.

                              • 12. Re: Wobbly edges after keying greenscreen footage
                                Dave LaRonde Level 6

                                reindeer4 wrote:

                                As for tone, I'll hold off from making any direct response to the snarkiness above and simply do what the poster suggested - click on the abuse button so you or one of the other folks at Adobe can take a more careful look at the thread and see if bogiesan is helping to create the type of atmosphere you want here on the forums.

                                 

                                ...or just develop a thicker skin. 

                                 

                                Bogesian was actually right in his initial comments, and I didn't think they were particularly snarky.  If you found them not to be helpful or too vague for your liking, that's because the combination of issues involving cameras, codecs, lighting, recording devices and budget boggles the mind.  You can neither expect nor rely on people here to know each and every one of those combinations, nor to diagnose your particular situation with anything approaching pinpoint accuracy.

                                 

                                After that minor hurdle, you get to the topic of chroma keying techniques in AE.

                                • 13. Re: Wobbly edges after keying greenscreen footage
                                  idar lettrem Level 1

                                  reindeer4: actually You don't need the rotobrush for this kind of footage.  You do the masking just as easy manually

                                  • 14. Re: Wobbly edges after keying greenscreen footage
                                    reindeer4 Level 1

                                    idar -

                                    I experimented with masking last night, and it does let me get rid of the wobbly edge problem (though as Todd pointed out in his post, it can get pretty tedious to do that manually).  Does give me a workable option though.  Thanks for the suggestion.