5 Replies Latest reply on Sep 18, 2012 1:20 AM by Stephen_Spider

    How do you re-encode h.264 video without artifacts?

    MrLoofer Level 1

      Hi

       

      I have a video that was exported out of Premiere using h.264 at max 20mbps. All is good. Since the export takes 10+ hours I now want to create a version for Vimeo and Youtube. Becuase of the file size I don't want to upload the entire 2GB file to these services (I have a 5GB week limit upload at Vimeo) so I'll simply bring the file back into Premiere and export it using the Vimeo or Youtube setting with the max mbps around 5mbps or so. When I do this the resulting output file is unplayable, lots of artifacts and stutters. Some blacks are white even. I'm guessing Premiere is having an issue becuase it's re-encoding an already coded h.264 file, or something like that. Any ideas why this would happen and any solution to producing a good output?

       

      Cheers.

        • 1. Re: How do you re-encode h.264 video without artifacts?
          Dave Merchant MVP & Adobe Community Professional

          Re-compressing an already compressed video file is never a good idea, so you're pretty much stuck with having to re-export - the 'correct' workflow would have been to export from Premiere Pro at maximum resolution and quality into a lossless or low-compression format (Quicktime or ProRes on OS X, DNxHD/Lagarith/UT AVI on Windows) then use that intermediate file in Adobe Media Encoder to create your various final copies.

          • 2. Re: How do you re-encode h.264 video without artifacts?
            RjL190365 Level 4

            As Dave stated, re-compressing already lossy-compressed video directly into another lossy compressed format is never a good idea: In this instance, image quality will degrade severely from that of the original AVCHD video. And all of the suggested intermediate files for Windows habe their disadvantages: DNxHD (and possibly UT) invoke the Apple QuirckTime API that induces a severe gamma shift in the encoded video (in the worst cases, whites come out medium-gray and middle tones come out pitch black) and is very slow to process due to it being restricted to 32-bit operations. Lagarith requires a massively powerful CPU - far more powerful than even a heavily overclocked i7-3960X - just to even play back well (this is based on my experience with Lagarith and my heavily overclocked i7-2600K, which dropped frames massively on playback of Lagarith-encoded material).

            • 3. Re: How do you re-encode h.264 video without artifacts?
              Jim_Simon Level 8

              DNxHD (and possibly UT) invoke the Apple QuirckTime

               

              DNxHD will, but UT goes into the appropriate (for Windows) AVI container.  And it does play back much better than Lags at HD resolutions.

              • 4. Re: How do you re-encode h.264 video without artifacts?
                RjL190365 Level 4

                This goes to show that I have never used UT. I might try it in the near future.

                • 5. Re: How do you re-encode h.264 video without artifacts?
                  Stephen_Spider Level 3

                  I just tested this on a 1 minute h.264 clip comprised of 15 complex shots & grfx.  The source H.264 seemed to be 720 @25fps and 5-8mbps variable. I output to H.264 vimeo HD preset and only changed the bitrate to constant 8mbps rather than variable. I'm suprised to say that I went 4 generations deep without really noticing and degradaion. I was able to see the slightest variations in the waveform, and a little more in the vetorscope. None of the genetrations looked soft or glitchy. Perhaps you used the qt wraper where I used .mp4?

                   

                  ps each export took 15-20secs,  max render quality unchecked 1 out of 4 goes with no significant change in output time.

                   

                  Maybe that helps. Good luck.