8 Replies Latest reply on Feb 4, 2015 8:04 PM by Rick Gerard

    Keying correctly with movement

    ben.a

      Hi there i'm using uncompressed 1920 x 1080 H.264 .mov. Not sure what camera sorry. Shot in front of a fairly well lit green screen.

      Using keylight 1.2 as I have on previous footage I get a terrible key most times. On still shots this seems to be a glare of green that pushes onto the subject and keys out hands etc... I'd love some advice or pointers on where to go to find out how to fix this.

       

      But my main concern is the key of feet walking across the screen. Black shoes and black trousers take one step into the shot and disappear with the other leg flying past. This creates a blur and make the key grainy and un usable? Does anyone know what I can do to fix this?!?!? Any help would be hugley recieved I have a few days to come up with a solution!? I'm just trying to key it onto a white background and am working on a reflective floor for it to step on to?

        • 1. Re: Keying correctly with movement
          Mylenium Most Valuable Participant

          Hi there i'm using uncompressed 1920 x 1080 H.264 .mov.

           

          Erm, that's an oxymoron - for all intents and purposes, H.264 is compressed and quite heavily at that and it very much explains all your problems/ oddities/ difficulties.

          I'd love some advice or pointers on where to go to find out how to fix this.


          Don't use compressed formats for keying, plain and simple. And if you can't avoid it, spend time pre-processing your footage, that is apply techniques or plug-ins to remove block artifacts, sharpen edges, even out the screen color and all those little unimportant things. Other than that  there's no point in looking for magic buttons - each key is different and takes time to get right, but as I already wrote, for the time being you are laboring under wrong assumptions and that's no doubt one of the reasons why you haven't been able to get a good result...

           

          Mylenium

          1 person found this helpful
          • 2. Re: Keying correctly with movement
            ben.a Level 1

            hey thanks for your reply. Well it's the footage given to me by the camera man and I assume it's not been compressed as he had a folder full of 422 compressed versions and these were in the one marked uncomp. H.264 was a detail given to me from opening it in Quicktime? I seem to have much better luck using the Ultra key in Adobe Preimere?? As I was able to turn the floor white without much change to the shoe and this is what I was going for.

             

            So are you saying sharpening the footage will give it smoother movement coloring can sort out the movement! Thanks again!

            • 3. Re: Keying correctly with movement
              ben.a Level 1

              Sorry last little question- I've lookd into the footage earlier and it might be that he has converted them from MOD files to the H.264 Millions of colors.mov format. If this is the case ill have to convert them either way. What's best for green screen - Uncompressed, Codec 422 or something else?

              • 4. Re: Keying correctly with movement
                Navarro Parker Level 3

                So first of all, if it's h264, it's compressed. Uncompressed h264 is like saying dehydrated water. And all consumer cameras that shoot h264 use 4:2:0 which makes for terrible keying.

                 

                Keying feet are notoriously difficult to light and key well. It sounds like you need to dive into the tedious waters of rotoscoping. Or, reshoot it. Or, think about reframing the shot in AE, or putting something in the foreground to obscure feet.

                 

                As far as green spill, all good chromakeyers should have that function built-in and are usually amazing at suppressing green on your subject. Are you using Keylight?

                • 5. Re: Keying correctly with movement
                  bogiesan Level 4

                  All excellent advice so far. convert the H.264 to a frame-friendly editing format like ProResLT if you're on a Macintosh. The best keys are, as Myl noted, accomplished with multiple copies of your footage, each processed differently and exchanging alpha information, to produce a seamless key. You are probably dealing with two additional issues trying to process the highly compressed H.264: as it is unwrapped into frames, lots of information is interpolated because it's not really there so adjacent frames will have different pixels and the same guy who handed you highly compressed green screen footage probably had absolutely no clue about shooting at fast shutter speeds to minimize image blur.

                   

                  bogiesan

                  • 6. Re: Keying correctly with movement
                    ben.a Level 1

                    Wow thanks for the advice. I have doubled up the footage with different key settings and that took away allot of the pixelating. Great help Bogiesan. I don't suppose there is a way i can fake fast shutter speeds to reduce the blur. But yes that sounds like the issue! Again thanks very much for all your help, i now have footage in apple 4444 but i've no idea how this has been created as the difference seems almost non exsistant?

                     

                    Oh and yes I've been using keylight for most of the dancing shots. Just Ultra key for the Shoe as it looked so much better!

                    • 7. Re: Keying correctly with movement
                      Videohead

                      I key H.264 footage all of the time and it works very well. Make sure you have good lighting and some physical separation between the subject and the background, which will prevent spillage and fringing.

                      Of course, light goes everywhere and you cannot make miracles - reflective or shiny shoes, and other problems. The GIGO rule always applies to any shot footage - garbage in = garbage out.

                      I get better results with progressive frame footage, so if you have a choice about how to set your camera, then that is great.

                      Sorry, but I could not disagree more about upconverting/up-rezzing your footage to ProRes, uncompressed, or 4:4:4. You are just wasting disk space and slowing down your system to deal with the disk read-write. Keylight is perfectly capable of processing well in the H.264 space (4:2:0). You cannot add bits that were not there in the first place so you won't gain any color space by adding a bunch of fake bits. Colorimetry does not lie - if you start in 8/10 bits, you may as well finish there.

                      • 8. Re: Keying correctly with movement
                        Rick Gerard Adobe Community Professional & MVP

                        Without seeing at least a frame of your footage it's hard to give you the exact settings but sometimes you have to just do the best you can then hand roto and color correct things like your problematic hands. This is why you should have someone that knows what they are doing shoot your green screen footage. These kinds of problems can very easily be solved on set but can take hours in post. I can't tell you how many keying projects I have had in my career that required some hand masking to complete. I'd say that most projects that I did not shoot had at least two copies of the original footage with different keying settings to generate a clean key.

                         

                        If you can pull an acceptable key in Premiere Pro then you should be able to pull an acceptable key in AE with the included tools, and with a little tweaking, produce a better key.

                         

                        As to the question about compressed footage, of course 10 bit 4:2:2 lossless or better original footage is better than 8 bit 4:2:0, but  if your compressed DI didn't introduce any compression or color artifacts then Re-rendering may not make much of a difference. If you have a higher bit depth or color sampled original footage then you should work with that. If you want to try improving the h.264 footage by rendering a production DI then pick a 10 bit 4:2:2 codec or better and have at it. You can get better results with that kind of DI if you need to seriously crank on color controls to pull your key.