4 Replies Latest reply: Nov 2, 2010 4:44 PM by Bill Hunt RSS

    CS4 exporting magic?

    seiurus Community Member

      I hope someone who knows a lot more than I do about codecs and compression can answer this question.  I imported footage from my Canon XLH1 (1440 x 1080), 29.97 fps, progressive mode, tape media, MPEG-2 compression on the tape with a 4:2:0 color space.  Without editing, I exported it as Microsoft AVI uncompressed onto a flash drive. The size of the file increased about 9 fold.  I sent it to a client.

       

      The client blew the scene up to intercut it with movie film, and was very happy with the quality. I was overjoyed...it was like magic.  When he tried to do the same with a clone of the original footage (cloned to tape), it was lesser quality.  Now I am not a genius, but can do the math.  When the camcorder records to tape using MPEG2 and 4:2:0, there is compression; data is lost.  Just because I exported "uncompressed" from CS4, I would hardly expect data lost in taping to be found somewhere and put back!  But how else to explain the quality of the exported footage. Is there some alternate universe where lost pixels are stored along with single socks and ball point pen caps, waiting to be recalled?  Can someone explain this happy accident?

        • 1. Re: CS4 exporting magic?
          Bill Hunt CommunityMVP

          Just a guess here, not knowing what settings the client used, but it is likely that that Export to tape created a compressed file, so you have MPEG compression (or similar) twice.

           

          Also, that file size increase is to be expected, as the original MPEG is GOP (Group of Pictures), while the AVI Uncompressed is full I-frame. This ARTICLE will give you a bit of background.

           

          If you can get the exact workflow and settings that the client used, someone here can likely point out exactly why the quality loss.

           

          Good luck,

           

          Hunt

          • 2. Re: CS4 exporting magic?
            JSS1138 CommunityMVP

            I would hardly expect data lost in taping to be found somewhere and put back!

             

            That is actually precisely what happens.  In fact, it HAS to happen or you don't have an image.  There isn't a display in the world that can show you a compressed image.  They all have to be decompressed back to RGB in order to show you the picture.

             

            The issue at hand is how closely the restored image is to the original.  Obviously, the more you throw out in compression, the more the decompression stage will have to "guess" at the missing data.  Those "guesses" are where artifacts, anomalies and other image degradations show up.  It is entirely possible that whatever method of decompression he used was creating inferior "guesses" compared to what Premiere was doing for the Uncompressed export.

            • 3. Re: CS4 exporting magic?
              seiurus Community Member

              Jim,

                   Thanks for your reply.  It still seems too good to be true.  Canon has told me that the compressed data on the tape is actually in 4:2:2 (although the official compression to tape is 4:2:0) and that the 4:2:2 information can be accessed by decompression software.  If that is true, I wonder why people spend so much money on devices like Nanoflash to collect 4:2:2 via HDSDI port?

               

               

              Steve Siegel

              mobile (305)343-2179

              answering service 24/7 (305)865-9861

              • 4. Re: CS4 exporting magic?
                Bill Hunt CommunityMVP

                Steve,

                 

                You might want to disable your signature in your posts (likely from e-mail), as personal data can be easily harvested in a public forum.

                 

                Good luck,

                 

                Hunt