Perian forces wrong aspect ratio

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dbb
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Perian forces wrong aspect ratio

Postby dbb » Wed Nov 26, 2008 11:06 pm

Hi

Just installed Perian in order to get AC3 audio working under Quicktime (I have VLC, but would rather Quicktime in this instance).

Audio now works, but it appears Perian is forcing the wrong aspect ratio on the movie. With Perian uninstalled, the aspect ratio is correct at widescreen (720x404). When installed, the aspect ratio is forced to 4x3. Quicktime info reports the following:

Format: Generic MPEG-4, 720 x 404 (606 x 404), Millions.

It is the forced aspect in brackets that is the problem.

I can workaround and correct the aspect ratio by resizing the Quicktime window using opt-shift. However, I'd like to know why this problem is occuring - if this is a known issue, or if I'm the first lucky recipient of a resize prize...?

Cheers.

Mr VacBob
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Re: Perian forces wrong aspect ratio

Postby Mr VacBob » Wed Dec 03, 2008 5:25 am

Sounds like your video is wrongly cropped (DVD source should be cropped to 704x480 then resized to 704x396), but either way post the file.

TDB
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Re: Perian forces wrong aspect ratio

Postby TDB » Wed Dec 10, 2008 2:06 pm

I've experienced similar problems with certain Divx/Xvid files.

The info box in QT reports Xvid (Perian) 640 x 352 (440 x 352), Millions, MPEG Layer 3, stereo, 48.000 kHz and displays in the 440 x 352 aspect ratio.

In VLC, however, it displays in the correct ratio.

Mr VacBob
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Re: Perian forces wrong aspect ratio

Postby Mr VacBob » Thu Dec 11, 2008 7:35 pm

Mr VacBob wrote:post the file

m1ss1ontomars2k4
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Re: Perian forces wrong aspect ratio

Postby m1ss1ontomars2k4 » Tue Mar 24, 2009 6:27 pm

I too am having this problem, with what I'd assume is a different video--it should be 720x400, but instead it's being forced to 600x400 by Perian. The file was originally AVI, but the only way I could get a sample was to save it to MOV. I have a sample in a (somewhat damaged) AVI container if you'd also like that.

http://m1ss1ontomars2k4.googlepages.com/superwhack2.mov

or change superwhack2.mov to sample.avi for the other one (URL limit reached; sorry)

Mirrors:

http://www.megaupload.com/?d=74FU4GUH (superwhack2.mov)

http://www.megaupload.com/?d=RMOPBN6N (sample.avi)

EDIT: I was unable to upload sample.avi to Googlepages; you'll have to use the megaupload link instead.
Last edited by m1ss1ontomars2k4 on Wed Mar 25, 2009 12:10 am, edited 1 time in total.

gbooker
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Re: Perian forces wrong aspect ratio

Postby gbooker » Tue Mar 24, 2009 7:39 pm

Opened sample.avi and Format is:
Xvid (Perian), 720 x 400 (600 x 400), Millions
AC3, 5.1 (L R C LFE Ls Rs), 48.000 kHz

That means it's encoded in 600x400 (that's the resolution the bitstream is at), but displayed at 720x400. Make sure you don't have other components installed, such as the xvid delegate or divx.

m1ss1ontomars2k4
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Re: Perian forces wrong aspect ratio

Postby m1ss1ontomars2k4 » Tue Mar 24, 2009 8:47 pm

No, actually, it's the other way around.

Well, I'm not sure what it's encoded at, but it's supposed to be displayed at 720x400--VLC reports that this is the resolution, and when played at this resolution, all the circles are, well, circular. It's definitely being displayed at 600x400 with QuickTime + Perian.

If you look farther down the information window, you'll see that it's being displayed at 600x400, not 720x400.

Unless I'm missing something, I don't have any other components installed that can play Xvid, and QuickTime reports Perian is being used to play it.

Mr VacBob
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Re: Perian forces wrong aspect ratio

Postby Mr VacBob » Tue Mar 24, 2009 9:27 pm

My mplayer plays sample.avi at 720x480, which is the same aspect as 600x400 (but a more reasonable size, that's QT internals though). The avi header says the aspect is 720/400, so I'm not sure what's going on there - I'll look when I'm not on battery power.

m1ss1ontomars2k4
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Re: Perian forces wrong aspect ratio

Postby m1ss1ontomars2k4 » Wed Mar 25, 2009 12:01 am

Well, I tried using the Xvid component available here: http://n.ethz.ch/~naegelic/download/

However, QuickTime still tries to display it at 600x400. For me, the last version of MPlayer OS X reports that the video is 720x400, but displays it at 720x480 as well.

gbooker
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Re: Perian forces wrong aspect ratio

Postby gbooker » Wed Mar 25, 2009 1:43 am

Sorry, I got the codec and display dimensions reversed.

I examined the AVI header. It defines the codec as having data in 720x400, but the header also defines the codec as having a display aspect ratio of 3:2. This is the aspect ratio of 600x400 and 720x480. Furthermore, the avi header defines a 720x400 display. Basically, the file is saying that a*b=c, where it defines a, b, and c, and both sides of the equation don't match. The question is which set of values is to be believed, and in our experience, when the aspect ratio is defined, it is correct where as the width/height info of the codec and the avi display are wrong.

m1ss1ontomars2k4
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Re: Perian forces wrong aspect ratio

Postby m1ss1ontomars2k4 » Wed Mar 25, 2009 3:42 am

Ah, thanks. I used a hex editor to make the necessary changes; the video is fine now.


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