How to prevent iMovie from horizontally stretchin movies when exporting full size?

Discussion in 'Mac Apps and Mac App Store' started by amin, May 17, 2004.

  1. amin macrumors 6502a

    amin

    Joined:
    Aug 17, 2003
    Location:
    Boston, MA
    #1
    Whenever I export from iMovie 4 to DV or full-size MPEG 4, the results are stretched horizontally. I've attached a screenshot showing the home movie with correct proportions playing in the foreground within iMovie and the exported result playing in quicktime in the background. You can see how my son's head is stretched. Is there any way to prevent this? If I export to 320x240 the proportions are somehow maintained. However, the grandparents like to see this stuff as large as possible.

    Thanks for any help.
     

    Attached Files:

  2. Makosuke macrumors 603

    Joined:
    Aug 15, 2001
    Location:
    The Cool Part of CA, USA
    #2
    The answer of "why" is easy; DV, the format that iMovie uses for everything it does internally, doesn't have square pixels. That is, it uses a format that is 720X480 pixels, even though the correct proportions for the image are 4:3 (640X480, 320X240, etc).

    This works fine because TVs don't have square pixels, either, and you get a better image by displaying 720X480 on a TV than you would from 640X480. Unfortunately, when you export at full quality from iMovie, it does give you full quality, but doesn't set the aspect ratio of the movie correctly, so when played on a computer monitor, it's stretched horizontally.

    There are two possible solutions. The easiest if you're exporting to MPEG4 is to export as 640X480 instead of full size; you won't loose much resolution, but you will end up with the correct size image. The other option is to take the movie you've exported, open it with Quicktime Pro ($30 from Apple, and well worth it), and resize the image from the 720X480 to 640X480, then save that. You've then got a full resolution image scaled into the correct aspect ratio.

    Note that if you're exporting as a .dv stream, you get what you get; the DV format (with NTSC) won't let you use any other resolution, and since it's a .dv stream instead of a quicktime movie, you can't use Quicktime Pro to save it with a different aspect ratio. You'll just have to resize it to a different aspect ratio when playing it (you can do this manually in QT Player by holding down Shift when dragging the corner), or play it with a player that knows what to do with .dv video.

    Hope that helped.
     
  3. amin thread starter macrumors 6502a

    amin

    Joined:
    Aug 17, 2003
    Location:
    Boston, MA
    #3
    Thank you soooo much Makosuke!!! I tracked down every Google result without finding an answer before I posted here, and you gave me the answer in just a few minutes. I tried both of your solutions, and resizing in QT Pro definitely produced noticeably better results in the end. Again, thank you for your help and especially for taking the time to explain the "why."

    I have two more questions if you or anyone else have time to answer.
    1) If TV pixels are narrower than they are high, and so are DV pixels, then why do DVDs look the same on TV as they do on my computer monitor? Is the software making the adjustment?
    2) When I export family videos from iMovie to iDVD, should I resize them somehow? I know you said that TV pixels are shaped like DV pixels, but I'm still concerned about documenting my family's precious moments in a format that makes everyone a fathead :).
     
  4. Makosuke macrumors 603

    Joined:
    Aug 15, 2001
    Location:
    The Cool Part of CA, USA
    #4
    Yes.

    You can see this most dramatically on those "anamorphic" widescreen DVDs; the video is still at most about 720X480, but is stretched way out to the correct aspect ratio on your computer (or on the proper kind of TV).

    It's more accurate, by the way, to just say that they aren't square; the DVD format actually allows sizes from 720X480 all the way down to 352X480 and 352X240, though I expect most professional DVDs go with the maximum.

    Absolutely, positively not. iMovie works in DV format, and iDVD does as well. They're designed to work together, and any attempt at overriding that integration is only going to degrade quality. Just trust that if you feed iDVD DV format video, which is the native format of iMovie, that it'll do what it needs to.

    If quality is important to you, I do recommend getting iLife 04; the newest version of iDVD has some good quality-increasing features. Putting an hour or less of video on a DVD is going to get you the absolute best quality, though.
     
  5. amin thread starter macrumors 6502a

    amin

    Joined:
    Aug 17, 2003
    Location:
    Boston, MA
    #5
    Thank you again Makosuke. I recently purchased both QT Pro and the new iLife, so I'm ready to document some family times :).
     

Share This Page