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  1. Member
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    I am trying to use ffmpegX to convert several .avi movies to .MP4 so I can put them in my iTunes library. When I open a file to convert and select .MP4 as the output format, it shows the output resolution in the box on the bottom right, and sometimes this resolution doesn't match the original .avi resolution. I have tried going under the Video tab and manually changing the output resolution to match the original file, but this doesn't seem to work and the result is a .MP4 that is stretched either vertically or horizontally. I have also tried several of the different aspect ratio options under the video tab but 9 times out of 10, I end up with a .MP4 that doesn't match the aspect ratio of the original .avi. Obviously I'm doing something wrong. My goal is a .MP4 output with the same resolution as the original .avi but without being stretched. Can someone please explain why, even when I manually change the resolution to match, the output is stretched? Thanks for any help.
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  2. Explorer Case's Avatar
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    Originally Posted by Agent Bauer View Post
    I am trying to use ffmpegX to convert several .avi movies to .MP4 so I can put them in my iTunes library. When I open a file to convert and select .MP4 as the output format, it shows the output resolution in the box on the bottom right, and sometimes this resolution doesn't match the original .avi resolution.
    This appears to be very similar to this post: https://forum.videohelp.com/threads/308434-Converting-Divx-AVI-to-MP4-Output-size-option-doesn-t-work
    For videos that have an aspect ratio that is not exactly 4:3 or 16:9, the converted MP4 file will be stretched to 4:3. Correct?

    Not sure if this issue is due to the age of ffmpegX, but it can be corrected easily and fast.
    You may set a pixel aspect ratio (PAR) of 1:1 with command line MP4Box to get the expected unstretched playback:
    Code:
    MP4Box -add source.mp4#trackID=1:par=1:1 -add source.mp4#trackID=2 target.mp4
    (Tested playback with QuickTime Player, iTunes, VLC and MPlayer.)
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  3. Explorer Case's Avatar
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    I was making it more complex than needed. The MP4Box command can be shorter:
    Code:
    MP4Box -add source.mp4:par=1:1 target2.mp4
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  4. Explorer Case's Avatar
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    You don't have to download and install a new version of MP4Box -- the one included in ffmpegX can do it too.
    Just replace 'MP4Box' with '/Applications/ffmpegX.app/Contents/Resources/mp4box' .

    Here's an AppleScript to do it all for you: MP4PARcorrector.app . The script assumes the location of /Applications/ffmpegX.app . For a different location or a different mp4box, change the script. (The app can be opened and edited in Script Editor.)

    Double-click MP4PARcorrector. It will ask you for an input file. The corrected "output.mp4" will be a new file in the same folder location.
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    Last edited by Case; 21st Mar 2010 at 10:45.
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