8 Replies Latest reply on Jun 1, 2010 12:16 PM by aimenyagami

    De-Interlacing - How bad is it?




      I'm having issues with Ghosting exporting movies from Premiere (see other post "Ghosting")


      De-Interlacing does seem to fix the problem, however, I've heard lots of people say you should never De-interlace as it's halves the vertical quality - How can you tell if this is the case? I've looked at both side by side and I can't tell a difference.


      Any help with this would be great, thanks



        • 1. Re: De-Interlacing - How bad is it?
          Harm Millaard Level 7

          If you can't see the difference, then who cares? You decide what is acceptable.

          • 2. Re: De-Interlacing - How bad is it?
            taz(UK) Level 1

            The clips get sold through an agency so they need to be of the highest quality.


            I can't tell the difference in my eyes, but I just wondered if there was any way of cheking the data etc.?



            • 3. Re: De-Interlacing - How bad is it?
              Harm Millaard Level 7

              The only negative effect of de-interlacing is that you throw away 50% of your vertical resolution, but if that is OK with you...


              Use some test chart from the internet if you want to test it.

              • 4. Re: De-Interlacing - How bad is it?
                taz(UK) Level 1

                Thanks for your replies harm, I obviously don't want to lose 50% quality, but it does cure the Ghosting problem.


                The thing I can't understand is that I can't see any visible loss of quality at all - Surely if the quality went down by 50% I'd be able to tell??


                Do you know whereabouts on the internet I can find a test chart?


                Also, where did you learn about the 50% loss? Was it from Adobe?


                Thanks again - I'd just love to get the bottom of this problem, without losing quality!

                • 5. Re: De-Interlacing - How bad is it?
                  Harm Millaard Level 7

                  Test charts can be found with Google. I don't have a link ready, but I'll have a look tomorrow.


                  To really test the quality, either burn to DVD and play on a TV or use a properly calibrated external monitor. The program monitor does OK for previews, but you can't judge quality of the end product on it.


                  The de-interlacing 'algorithm' in PR is pretty dumb. It throws away all (un)even fields (I always forget which ones) and just doubles the remaining ones.

                  • 6. Re: De-Interlacing - How bad is it?
                    Harm Millaard Level 7

                    I have been corrected with regards to deinterlacing in CS5 by Adobe.


                    Earlier versions CS4 and earlier were not as good as CS5 that has taken the deinterlacing to new highs.




                    Field doubling is  only used in low quality paths and never for final output. For actual  rendering we use the same deinterlacer as After Effects (both with and  without CUDA). For display purposes the deinterlacing can be somewhat  low quality (except when CUDA is on, which always uses the better deinterlacer that we use for  output). This is a good deal more complicated than field doubling but by  no means the end of the story. We could (and I hope we will) come up  with a much more complicated solution by calculating motion vectors between neighboring fields then performing optical flow  to interpolate the missing pixels (and maybe make it perform pretty well  with CUDA).


                    End of quote.


                    Now this is good news for CS5 users.

                    • 7. Re: De-Interlacing - How bad is it?
                      the_wine_snob Level 9



                      That IS good news regarding CS5.


                      Thanks for sharing,



                      • 8. Re: De-Interlacing - How bad is it?

                        ok about why you cant till the  difference? its BECAUSE pp already playing back video with de interlacing >>>>>>>>>>

                        do this :

                        1- before de interlacing ... on program monitor go to view zoom level and click 100%

                        2- you will see a black lines about 50% in the frame.

                        3- if you de interlacing ..... the black lines will disappear.(thats mean the video has interlaceing).

                        4- in this case if you see ghosting on external monitor (not program monitor in pp) you should reveres it. NOT de interlace it (so you fix it not lose quality) go to field option click reveres field dominance .

                        5- on external monitor you should see its ok now ...


                        sorry for my english.......