11 Replies Latest reply on Dec 22, 2014 9:09 PM by suncodr

    What are the benefits (if any) to transcoding to an intermediate editing format for post-production?

    suncodr Level 1

      I have been searching for a definitive answer to this for days and cannot get anything useful.

       

      My video camera records to AVCHD format which is 24mbps H.264 plus audio (I record audio separately so audio is not a concern). I use the Adobe CC suite on Windows. I do a lot of green-screen work.

       

      I have read about many intermediate codecs designed for editing video. These include Avid's DNxHD, Apple's ProRes, GoPro's Cineform, MXF OP1a, among others. From what I understand, these formats provide excellent features to help video editors do their work.

       

      I have been able to edit AVCHD files directly using Premiere Pro and After Affects.

       

      My question is, what benefits, if any, would I get if I transcoded my content from AVCHD to one of the intermediate formats before I begin editing? Would it speed up Adobe's software? Would it provide better quality in the end? Would it make various effects function better?

       

      Ultimately, all the video I make is going to be encoded in h.264 for web distribution.

       

      Please note: I am not asking for the easiest or most obvious workflow (which is to just to work directly with AVCHD files). I want to know if I can gain benefits in transcoding to another format before I being post-production and what those benefits are specifically for each of the various intermediate codecs.

       

      Thank you.

        • 1. Re: What are the benefits (if any) to transcoding to an intermediate editing format for post-production?
          Jude Cotter Level 2

          If everything is working for you to a level that you're happy with, then there is no need to transcode.

           

          Some reasons why you might want to work in another codec would include a better colour space - this can help with your greenscreen work, but if your results are already good, then it's not really necessary.

           

          One of the great things about Premiere CC is that you don't have to transcode to be able to work seamlessly. Most of those codecs you mentioned, though, are used for delivery to high end broadcasters, so if you needed to, you could export as an MXF or ProRes, depending on what the station required.

          • 2. Re: What are the benefits (if any) to transcoding to an intermediate editing format for post-production?
            suncodr Level 1

            Thanks for the reply, Jude.

             

            In general, I do have some issues. I have found work-arounds so these are not major issues, but I do believe they may be tied to the codec.

             

            For example, using After Effect's Keylight (and to a greater extend Ultra Key), I find the parts of of my video that are left in after keying (the people in front of the green screen) have significant amounts of noise that was not there before the key. In other words, the green is gone but the parts that are left have significant noise. I learned a technique that involves extracting a matte created by Keylight and using it to maintain the original details rather than the over-processed raw Keylight effect. The technique is described in this YouTube video: Advanced Green Screen Keying [After Effects Tutorial] - YouTube

             

            If I could get similar results to the above technique using a better codec without the work-arounds, it would definitely be worth it to me.

             

            Do you know anywhere I could get some definitive details on what the benefits of the different formats are and if any one is considered to produce exceptionally good edited video? I may need to just do my own extensive tests, but I wanted to check in here to try to get a jump on the research.

            • 3. Re: What are the benefits (if any) to transcoding to an intermediate editing format for post-production?
              Jude Cotter Level 2

              Well, each format has its own benefits and drawbacks. The higher end codecs tend to be very large and take much more storage space, but behave better when applying effects or doing greenscreen work.

               

              However, you can't really improve the quality that comes out of your camera, so that is an imperative part of the workflow. You CAN transcode to, say, ProRes HQ, and get better results with your fx work, but it won't ever be as good as something shot on a higher end camera.

               

              Maybe do some tests on one short piece of video. Transcode it into several codecs and do exactly the same process to all the clips, including your original. Then compare and see if the improvement is worth your time and extra hard drive space.

              • 4. Re: What are the benefits (if any) to transcoding to an intermediate editing format for post-production?
                shooternz Level 6

                Can you post a frame grab of a green screen scene that is cause you trouble (noise).

                 

                Before and after key examples would be good.

                 

                FWIW - you should have no problems or issues pulling keys off properly shot AVCHD chroma screen footage.

                 

                Transcoding it wont help.

                 

                AVCHD footage -  keyed scenes.

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                • 5. Re: What are the benefits (if any) to transcoding to an intermediate editing format for post-production?
                  R Neil Haugen Adobe Community Professional & MVP

                  Like almost everything, there's tradeoffs. Transcoding to a really high-end single-file codec like Cineon or Cineform would mean that say the file size could be somewhat larger on disc ... more data to read ... however, LESS work by the other subsystems to get those io oo ii oo oo io io io oi bits changed into "video" on the monitor. There are several articles and tutorials out there on this that give really useful information. And there are a LOT of people that put something out because they personally think this or that codec is THE proper way a professional should work, and any other codec is nearly obscene in use. Right, whatever. They're all tools.

                   

                  As shooternz showed ... properly shot AVCHD can be green-screened beautifully, and as there are a LOT of the "pro" cameras in use shooting that wrapper, there are a lot of people that simply process in that. There are others that automatically transcode everything to ProRes 4444 before editing because they feel that gives them the best, safest "space" for their pixels to live. Pick any major codec/wrapper, it will have adherents.

                   

                  I've tried just a bit of greening just to play with it ... and got rather intriguing results. It reminded me of starting out trying to do good still portraits on high-key sweep backgrounds without getting "haze" or scatter from too-much-light coming back at the lens while getting the right exposure on the subject and keeping the entire high-key area of the sweep the same white ... it's rather daunting at first. After we mastered it, we could do it at will ... first time every time. Green-screening is a similar thing. Perhaps on steroids, but similar. HOW it's shot is incredibly important to being able to post-process both cleanly and quickly. I've seen quite a few comments about this here and elsewhere ... and though there are clean-up & masking techniques one does need to master, clearly ... one needs clean footage to be able to quickly get clean post work. So many people have noted that after spending so much time working on their masking & color-correction of bits here & there they also got their shooting skills up. And found that suddenly they didn't need anywhere near the clean-up skills or time spent.

                   

                  So I'd think off-hand that the AVCHD isn't the most pressing problem here ... that a bit of experience in the absolute tight control of exposure and lighting in the shooting setup may well take care of much of the post problems. And then you can concentrate on those skills you do need ... the fine techniques of this particular process ... to get your work completely polished.

                   

                  And listening to shooternz on this isn't a bad thing at all ... his techniques are tight & fast. I've asked him for a number of things and have adopted every one of them.

                   

                  Neil

                  • 6. Re: What are the benefits (if any) to transcoding to an intermediate editing format for post-production?
                    Jude Cotter Level 2

                    To be clear, to the best of my knowledge, the AVCHD colour sample ratio is 4:2:0, and that's not optimal for intensive colour work or greenscreening. As I said, if you're happy though, and I'm not at all saying the results are rubbish, then there's really no need to bother with transcoding.

                    • 7. Re: What are the benefits (if any) to transcoding to an intermediate editing format for post-production?
                      R Neil Haugen Adobe Community Professional & MVP

                      Jude's comment is why some of the GH4 people I've "forumed" with shoot 4k, then transcode to ProRes to get a 10-bit 422 file. In fact, that whole bit about being able to get a legit 1080p 4:2:2 file out of the thing through the transcode is why several got the camera. There are people green-screening off "standard" mov's from the GH4, but those who've done both prefer the higher color bits.

                       

                      Neil

                      • 8. Re: What are the benefits (if any) to transcoding to an intermediate editing format for post-production?
                        suncodr Level 1

                        Thank you all for your comments. I did some testing, transcoding to several formats including those mentioned and lossless ones. As Jude originally mentioned and others have concurred, transcoding does not give me better results. Poor footage is poor footage.

                         

                        Before moving further, I think I need to work on my setup.

                         

                        I will start with lighting.

                         

                        In addition, I find that when viewing a "live" HDMI feed from my cameras prior to and while recording, the picture quality is beautiful on my large, 1080p TV that I use as a monitor. However, once it's recorded to SD cards (using AVCHD) the picture gets noisy, less color rich, and darker (I'm using consumer grade Canon camcorders which may be part of the reason). I suspect part of my troubles have to do with AVCHD and/or the way my camcorders record video. I have found that I can purchase "clean HDMI" (a lossless signal) recorders that can capture HDMI in a better format than AVCHD (like those I originally mentioned) or even lossless video. I'm looking at the Blackmagic Decklink series specifically but there are many others.

                         

                        Once I've fixed my setup, I'll do some more testing and hopefully will get better results. Until then definitely agree transcoding will not give me better quality if my original files are poor.

                        • 9. Re: What are the benefits (if any) to transcoding to an intermediate editing format for post-production?
                          shooternz Level 6

                          Transcoding 4:2:0 to 4:2:2 or 4:4:4  does not magically make information (image data or data rate) appear from nowhere.

                           

                          Its 4:2:0 padded out  to fill the "data spaces" (data per pixel)

                          • 10. Re: What are the benefits (if any) to transcoding to an intermediate editing format for post-production?
                            R Neil Haugen Adobe Community Professional & MVP

                            If it were a "straight" transcode between spaces, no. That wasn't what I was referencing, however. In transcoding down from 4k to 1080, as has been explained in quite a number of articles, you do get actual 4:2:2. I thought it was stupid talk at first. Looked it up ... surprisingly, it's true.

                             

                            Neil

                            • 11. Re: What are the benefits (if any) to transcoding to an intermediate editing format for post-production?
                              suncodr Level 1

                              After some more research I've learned anything over HDMI is either 4:4:4 or (more likely) 4:2:2. So having a camera that records AVCHD (4:2:0) and an HDMI output, adding an external recorder to capture the HDMI output can result in recording better images than using the camera's recording feature. I am guessing this is why the live images on my monitor look so much better than my recorded images. Of course there is an argument to me made about taking all that money and spending it on a good camera in the first place . . .