Before I buy QTPro... (pixel shape question)

Discussion in 'Mac Apps and Mac App Store' started by mrgreen4242, Feb 13, 2007.

  1. mrgreen4242 macrumors 601


    Feb 10, 2004
    I've got some MP4 files I created with VisualHub and I think the pixel shape is somehow set incorrectly. QT and iTunes display the video correctly, but the aspect ratio is wrong on my iPod and on VLC. The file is the correct number of pixels on each axis, but displays incorrectly on some players.

    So, any application that will reset the pixel shape in the header without reencoding the video? Will QTPro do it? I'd consider buying it if I was sure it would do what I need (I also have this problem playing some .avi files on my multiformat DVD player, so this feature alone would be worth the $30), but since there's no demo I can't be sure. Can anyone help out with some advice, whether it be about QTPro or another app?
  2. balamw Moderator


    Staff Member

    Aug 16, 2005
    New England
    Have you played with the widescreen setting on the iPod?

  3. mrgreen4242 thread starter macrumors 601


    Feb 10, 2004
    Yes, the video is "squeezed"/letterboxed with widescreen on (which it shouldn't be - should be almost the full display) and the sides are cropped off (but the aspect ratio is corrected) with widescreen off.

    As I said, the file is the right size (resolution wise) and plays fine in QT/iTunes. Only the iPod (and later testing with VLC) show that the pixel shape is wrong (at least that's my best guess). I THINK QTPro will change the header of an MP4 file without transcoding anything so should fix it... I think. I believe that I read you could take a file that was, for example, an MP4 and save it as a .mov so you could bookmark it, etc, without transcoding, which indicates you can do some stuff without have to re-encode the video.

    I wish Apple would offer a 14-day trial of QTPro. :(

    EDIT: The WT7 User Guide PDF from Apple talks about changing the "aperture" of a video file to, among other things, change pixel shape. Could someone maybe try that out and see if you can change the shape of a video without transcoding it? I'm assuming QT/iTunes plays it right because MOST video decoders ignore pixel size, but the iPod doesn't, I assume because it knows what the exact display its playing back on looks like? VLC is just a good standards compliant player, so it probably looks at pixel shape as well.

    EDIT2: MPlayer OSX also displays is "squashed"... it's got to be pixel shape!
  4. mrgreen4242 thread starter macrumors 601


    Feb 10, 2004
    Wanted to correct that and fish for some more help... the aspect ratio is wrong regardless of setting, it just either letterboxed or cropped on the iPod, depending on the widescreen setting. The file is 320x240, though, so shouldn't do either.

    I'll probably end up buying QTPro tonight and just try it out, but I'm hoping someone can help... hrm, actually, I wonder if the TV production crew I work with has QTPro on the work machine - they have FCP HD, so maybe. At least that would save me $30 just to see if it works.

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