9 Replies Latest reply on Sep 16, 2009 10:03 PM by rdbenfield

    Preview/Titles are incorrect resolution and aspect ratio

    rdbenfield

      Hello,

       

      This may be a know behavior and it may be acceptable. I just cant find anything to say for sure that it is supposed to be this way or if I have a problem. The behavior in question is that when I am in PP the preview panel renders at the incorrect resolution. So for a standard DV - NTSC, the source and resulting resolution are 720x480 with a ratio of 1.5:1. However, the preview panel is rendering at 655x480 which is a ratio of 1.36:1. I dont think that is such a big deal, but I do need to know if it is an expected behavior. Also noteworthy (and possibly more of a problem) is that while sources appear to be slightly squished in the preview, Titles which are added are not squished. That would be fine, except that when exported/rendered, the titles get stretched out slightly.

       

      Ok, that said, here is some additional information that may (or may not) help:

       

      Hardware:

      Dell Precision T5400

      2 x Quad Core Xeon 2GHz E5405s

      4GB of RAM

      2 x 147GB 15k RPM SAS drives (each drive has a single volume, no RAID in use)

      1 x Dell SAS 6/iR SCSI controller

      1 x NVIDIA Quadro FX 1700

      2 x Dell 1908FP 19" LCDs

       

      OS/Software:

      Windows XP Professional 32 Bit, SP3

      Adobe Premiere Pro CS4, Version 4.1.0 (113 (MC: 166418))

       

      Steps for Test 1 - PP Title Test

      Created a new project using the DV - NTSC, Standard 48kHz preset.
      Created a new Default Still, Title.
      Within the Safe Margin, created a perfectly round white circle (shift drag) and centered it.
      Within the white circle, created a perfectly square black rectangle (shift drag) and centered it.
      Added the title to the sequence and expanded it to 15 seconds.
      Selected the preview panel and pressed the tilde key.
      Took a screenshot and cropped it to only the black back ground portion (the actual preview) and saved as bitmap.
      Pressed tilde again to revert to the normal view and selected File, Export, Media.
      Selected Windows Bitmap for the Format and NTSC Bitmap for the preset and saved it.
      Results to follow

      Steps for Test 2 - Imported Pattern Test

      Using an image editor, created new blank image with a 720x480 canvas.
      Created a perfectly round black circle against a white background.
      Created a perfectly square white rectangle in the black circle.
      Saved it as a 24 bit Windows bitmap for use in a sequence.
      Created a new project using the DV - NTSC, Standard 48kHz preset.
      Selected File, Import and opened the test pattern bitmap.
      Added the imported bitmap to the sequence and expanded it to 15 seconds.
      Selected the preview panel and pressed the tilde key.
      Took a screenshot and cropped it to only the black back ground portion (the actual preview) and saved as bitmap.
      Pressed tilde again to revert to the normal view and selected File, Export, Media.
      Selected Windows Bitmap for the Format and NTSC Bitmap for the preset and saved it.
      Results to follow

      Results for Test 1 - PP Title Test

       

      Previewed Measurements (Attached as "Test 1 - PP Title Previewed.bmp")
      Circle - Width and Height were Correct 378 x 378 pixels
      Square - Width and Height were Correct 275 x 275 pixels
      Canvas - Width and Height were Incorrect 655 x 480 pixels

      Rendered Measurements (Attached as "Test 1 - PP Title Rendered.bmp")
      Circle - Width and Height were Incorrect 415 x 378 pixels
      Square - Width and Height were Incorrect 303 x 275 pixels
      Canvas - Width and Height were Correct 720 x 480 pixels

      Results for Test 2 - Imported Pattern Test

       

      Source Measurements (Attached as "Test 2 - Imported Pattern Source.bmp")
      Circle - Width and Height were Correct 477 x 477 pixels
      Square - Width and Height were Correct 330 x 330 pixels
      Canvas - Width and Height were Correct 720 x 480 pixels

       

      Previewed Measurements (Attached as "Test 2 - Imported Pattern Previewed.bmp")
      Circle - Width and Height were Incorrect 434 x 477 pixels
      Square - Width and Height were Incorrect 301 x 330 pixels
      Canvas - Width and Height were Incorrect 655 x 480 pixels

      Rendered Measurements (Attached as "Test 2 - Imported Pattern Rendered.bmp")
      Circle - Width and Height were Correct 477x477 pixels
      Square - Width and Height were Correct 330x330 pixels
      Canvas - Width and Height were Correct 720x480 pixels

      I have attached a zip file with the bitmaps described above.

       

      Any anyone confirm this behaior as to whether or not it is normal? I am less concerned with the fact that it is a little squished in the preview panel, and a little more concerned with the fact that titles are stretched when rendered. I am guessing that there may be other things which are added by PP similar to the titles which are distorted slightly when exported.

       

      Any information would be greatly apprecaited.

       

      Regards,

      Richard

        • 1. Re: Preview/Titles are incorrect resolution and aspect ratio
          rdbenfield Level 1

          Sorry, i might should have also mentioned that when I say "I selected the preview panel and pressed the tilde key" to maximize the preview panel, I had it set to Highest Quality and 100%. And both LCDs are running at their native 1280 x 1024 resolution.

           

          Thanks,

          Richard

          • 2. Re: Preview/Titles are incorrect resolution and aspect ratio
            Harm Millaard Level 7

            So for a standard DV - NTSC, the source and resulting resolution are 720x480 with a ratio of 1.5:1.

             

            This is not possible. Standard DV has a PAR of 0,9 for 4x3 or 1,21 for 16x9. Your setup is incorrect.

            • 3. Re: Preview/Titles are incorrect resolution and aspect ratio
              rdbenfield Level 1

              Sorry, I should have been more clear. I am referring not to the pixels aspect ratio, but rather to the aspect ratio of the frames resolution. i.e. 720/480 = 1.5 and therefore the frame's resolution is 1.5:1. Where as 655/480 = 1.364583 and therefore the frame's resolution is 1.36:1.

               

              Thanks,

              Richard

              • 4. Re: Preview/Titles are incorrect resolution and aspect ratio
                Harm Millaard Level 7

                Standard DV is 640x480 with square pixels. Start from there and read about PAR, that will help you a lot. You are currently mixing apples and oranges.

                • 5. Re: Preview/Titles are incorrect resolution and aspect ratio
                  rdbenfield Level 1

                  Harm,

                   

                  Thanks, and I apologize for the confusion of referencing the aspect ratio. Please excuse the error and disregard the mention of it. The problem however remains the same. The resolution changes from (720 x 480) to (655 x 480), and then back to (720 x 480). This causes distortions and that is what I am concerned about.

                   

                  Thanks again,

                  Richard

                  • 6. Re: Preview/Titles are incorrect resolution and aspect ratio
                    Harm Millaard Level 7
                    However, the preview panel is rendering at 655x480 which is a ratio of 1.36:1.

                     

                    How can that be when your project is set up as standard DV? Is the program monitor set to fit and how do you establish the resolution on the program monitor?

                    • 7. Re: Preview/Titles are incorrect resolution and aspect ratio
                      rdbenfield Level 1

                      Hi Harm,

                       

                      Thanks again for your patience. I am not entirely sure what you mean. ("How can that be when your project is set up as standard DV?" and previously "Standard DV is 640x480"). Maybe I should not have said "Standard" I was not referring to "Standard Definition" I was referring to the name of the preset within PP. If I go into File, New, & Sequence, I am presented with presets. Among these is "DV NTSC", which contains "Standard 48kHz". That is what I am choosing, as seen below:

                       

                      Presets.PNG

                       

                      Which shows the following settings:

                       

                      DV NTSC - Standard.PNG

                      Frame size: 720h 480v

                       

                      When I check the properties of the source media I use, it shows a resolution of 720 x 480. Likewise, when I look at the properties of the media I export, it shows a resolution of 720 x 480.

                       

                      As for the program monitor, no, the magnification is not set to "Fit". It is set to "100%".For measuring, I used two methods. The primary means is just to perform a screen capture of the program monitor window, paste into an image editor, and use it to measure the actual display area. The second method was to JRuler available from http://www.spadixbd.com/freetools/jruler.htm. These have both proved accurate and consistently show a resolution of 720 x 480 for the frames of the source and resulting media. They likewise show that while objects in the source media is only distorted in the program monitor, not the final output, that is not the case for the objects I create as Titles within PP. I hope that helps make it more clear.

                       

                      Regards,

                      Richard Benfield

                      • 8. Re: Preview/Titles are incorrect resolution and aspect ratio
                        Harm Millaard Level 7

                        You may have misunderstood me when I said:

                         

                        Standard DV is 640x480 with square pixels.

                         

                        720 x480 with a PAR of 0,9 equals 640 x 480 with square pixels.  The PAR means the horizontal pixels are elongated resulting in rectangulars instead of square pixels. 720 x 0,9 = 640 (rounding errors aside). I think your whole confusion is due to a lack of understanding PAR in video. It is completely different from PS, where pixels are commonly used as square pixels, not with different PAR's. The same way that a lot of people often talk about DPI, which is completely meaningless in video but very relevant in printing.

                         

                        I think you can make your problem a lot clearer to us if you first read a bit about pixel aspect ratios and then try to explain it again. This may sound condescending and it is not meant to be, but I have some trouble understanding what you really mean.

                         

                        BTW, this whole confusion may be attributed to the fact that BMP's use square pixels.

                        • 9. Re: Preview/Titles are incorrect resolution and aspect ratio
                          rdbenfield Level 1

                          Well now you've done it... you made me read AND think... That's a dangerous combination with me....

                           

                          Ok, Harm you were Right... And you were Wrong...

                           

                          In fact the answer was in reading more about Pixel Aspect Ratios. I had to read and read and read... and then read a little more. The problem seems to be the complete lack of consistency as to the terminology and the math behind it. Where AR = Aspect Ratio, I have found information on...  Sample AR, Image AR, Picture AR, Pixel AR, Frame AR, Display AR, some of them are used incorrect. Most of them are explained inadequetly. And the math never worked. Ok, well sometimes it worked, but when it did, it said that the PP preview was incorrect. At 655x480, it just always came out wrong. So let me sum up what I believe I learned and maybe help someone else out that may search and find this thread later. Some of this I had known for a long time, some of it was a new found application of the old knowledge. Anyway, here is my summary of it.

                           

                          Aspect Ratio is the quotient of somethings width and height.

                           

                          SAR or Sample AR, Image AR, Picture AR, & Frame AR all appear to be the same, that being the aspect ratio of the picture or videos resolution. So a video with a resolution of 720 x 480 will have an SAR of 1.5.

                           

                          DAR or Display AR is the aspect ratio that an image is displayed at. If the image is displayed full screen then it is also the aspect ratio of the display device. If the display device uses square pixels then it is also the aspect ratio of the images displayed resolution. So an image displayed at a resolution of 640 x 480 will have an DAR of 1.333 (repeating).

                           

                          PAR or Pixel AR is much more difficult. I have seen it defined as the aspect ratio of the actual pixel. I have also seen it defined as the quotient of the SAR and the DAR. While I kept on inferring that these were only related to the playback pixels, they are also applicable to the capture pixels. So the capture device or resultant image also has a PAR. So if the capture/image PAR and the playback/display PAR dont match, the image will not look right.

                           

                          I finally stumbled upon a web page directly from Adobe that explained some additional and VERY important things. Here is the link for any who may want to see it: http://help.adobe.com/en_US/PremierePro/4.0/WS03BF7479-8C7B-4522-8C75-210AD102524Ea.html

                           

                          Among the things it explains is that DV NTSC is .91 and that PP will show the PAR it believes an file is based on. When I create a sequence it asks what preset to use. When you look at the DV NTSC, it shows the PAR is actually .9091. When I import a Type 2 DV video, it shows that its PAR is .9091. When I import a bitmap, it shows that its PAR is .9091... (Did you catch that?) As correctly noted by Harm, the bitmaps PAR is actually 1 not .9091. Thankfully, that same web page explains that you can manually correct the PAR by using the Interpret Footage dialog box. Immediately upon chaging the bitmaps PAR it was re-rendered in the program monitor correctly.

                           

                          Well that is all fine and well, but what about this 655 x 480 business in the program monitor? It just didnt make sense... until I calculated the PAR for a 720 x 480 SAR and a 655 x 480 DAR. The result? A PAR of .909722... Finally, it makes sense. A little more math showed me that 655 x 480 using square pixels is as close as you can possibly get to a PAR of .9091... So there it is... mystery solved. So in fact, it would appear that PP program monitor is the only player on my computer that will accurately display a 720 x 480 video with a PAR of .9091 such as Type 2 DV... the other players I kept using as a reference were displaying it with an incorrect PAR of 1. The only thing that PP did wrong. was assume that my bitmap had a PAR of .9091 instead of 1. But since it has an easy method to manually change the clips PAR. its point Adobe...

                           

                          Thanks,

                          Richard Benfield