7 Replies Latest reply on Mar 30, 2012 12:09 PM by Steve Grisetti Branched from an earlier discussion.

    Re: Confused about pixel aspect ratio

    JMBinCO

      It seems kind of dumb to be talking about std 0.9091 aspect ratio for D1/DV when PE itself specifies 720x480 as its own std MPEG/DVD output. If you capture video using PE and output the file to your PC, it will end up as 720x480 mpg, not 704x480. Hence the correct aspect ratio for import would be 0.8888 and not 0.9091. And why not simply offer both as an "interpret footage" input option?

       

      I have worked with all my std def avi/mpg files, and they all seem to import using the 0.9091 option such that they are wider than 4:3. Hence I can overlay a video over a 640x480 image, and it appears wider by ~ 15-16 pixels. This makes sense since 720 x 0.9091 (640/704) = 654.55. But using correct aspect ratio conversion of 720 x 0.8888 (640/720) = 640 of course.

       

      C'mon PE, please allow std def images & videos to play nice together!

        • 1. Re: Confused about pixel aspect ratio
          Steve Grisetti Adobe Community Professional

          You make a good point! 640/720 does not equal .9099. But that's the standard PAR for NTSC video.

           

          This Wiki article does a good job of explaining why the math is a little off.

          http://en.wikipedia.org/wiki/Aspect_ratio_(image)

           

          I'm not entirely convinced myself. But all that matters to me is that, in my experience, 720x480 with NTSC PAR produces a 640x480 Storage PAR and vice versa.

          • 2. Re: Confused about pixel aspect ratio
            the_wine_snob Level 9

            This ARTICLE has a link to Adobe's explanation on how it handles PAR.

             

            Hope that helps,

             

            Hunt

            • 3. Re: Confused about pixel aspect ratio
              the_wine_snob Level 9

              This ARTICLE has several links on all things DVD.

               

              Lot of good info in those.

               

              Hunt

              • 4. Re: Confused about pixel aspect ratio
                JMBinCO Level 1

                Unfortunately, PE has allowed the std 640/704=0.9091 mess up the 640/720=0.8888 conversion process. Lumping these two different PAR together is a mistake as if "close enough" is good enough. It's simple math and produces a problem.

                 

                Just do the following simple example. Try to put 3 .mpg(s) side-by-side on a 1920x1080 AVCHD video. You would hope to get 3 x 640 = 1920 perfectly aligned videos. However, you get overlaps. This shows up the worst when fading in/out the videos because the overlaps are additive. If I have to add a crop to correct this, don't you think PE should add the correct PAR setting instead?

                 

                So why even default to 0.9091 anyways when most mpg is 720 vs. 704. I've never even come across 704 yet.

                • 5. Re: Confused about pixel aspect ratio
                  Steve Grisetti Adobe Community Professional

                  Sorry if we're confusing actual requests for help with rhetorical questions, JM. But every source I've seen using the aspect ratio of .9 for NTSC video. Can you direct us to a place where they're indicating a video editor or processor that works in .888?

                  • 6. Re: Confused about pixel aspect ratio
                    JMBinCO Level 1

                    So I'll try to be more clear on the request for help. No, I have not seen an editor offering 0.8888. However, this is where PE could help. The 0.9091 comes from 704x480. And yet even CCIR601 specs 720x486, yet another PAR of 0.9. But why do we go back to these ancient analog based PARs? Why not use current DV/DVD camera PAR of 720x480 which needs to be scaled by 0.8888? Like I said, there is a real problem created by this. I think the problem is not noticed when creating stddef movies because the extra pixels just get clipped by the display size. But now that we have HD res, and you can mix all types of aspect ratio based videos & images, what you really want to be able to work with is 4:3 & 16:9, maybe even 3:2 etc. But what you don't want is 720x480 scaled by the 0.9091 to produce 654x480 such that it's slightly bigger than 640x480 (perfect 4:3). With this, you now have the problem of not being able to overlay a close-to-4:3 stddef video with 4:3 images.

                     

                    Given that PE seems to offer lots of std PARs, it would seem simple to offer a custom ratio. That's what help I need. Ability to use std mpeg/dvd movies and perfectly align them or overlay them with other perfect 4:3 images. Let's not mess up the math because 720x486, 720x480, and 704x480 all seem to get lumped into the same conversion. Should I use the transform effect to scale just the X direction?

                    • 7. Re: Confused about pixel aspect ratio
                      Steve Grisetti Adobe Community Professional

                      It's going to be tough to change the whole industry's standards -- especially starting with little old Premiere Elements. (Premiere Pro and Final Cut, maybe...)

                       

                      But I do appreciate your math! It certainly makes sense.

                       

                      (BTW, you CAN create custom output sizes using standard aspect ratios and square pixels in Premiere Elements by clicking on the Advanced button from any Share destination.)