Why is PAL MPEG2 720x540, not 720x576?

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Level 1

30 points

Why is PAL MPEG2 720x540, not 720x576?

I'm embarassed as I feel I ought to know this by now, but having just upgraded to the new FC Studio and Compressor 2, I'm all confused...

I work in PAL. D1-PAL is 720x576. Non square pixels. Happy with that. My DV and DVCPRO50 movies are all the same.

Yet my resultant MPEG2 files from Compressor report -via QuickTime Player - that they're 720x540 (a 4:3 ratio assuming Square pixels). Now, where did those extra 36 lines go?

Posted on Oct 9, 2005 9:10 AM

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Answer 1

Giorgio

Level 1

20 points

Oct 9, 2005 12:24 PM in response to Matt Davis

Hi Matt, I am in the same boat !
My MPEG2 file for QT is 720x540, but this same file imported in DVDSP 4.0 (Assets Window) the dimensions are 720x576 !!
Matt, try to import your file in DVDSP 4.0 and control the dimensions.
For your information, I burned a DVD with my file and the result was ok.
Perhaps a bug in QT ?

Giorgio

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Answer 2

Waymen

Level 5

5,722 points

Oct 9, 2005 9:32 PM in response to Matt Davis

QuickTime just does that for display purposes so that your MPEG movie has the correct aspect ratio when viewed on your square-pixel computer monitor. It also converts NTSC's 720 x 480 to 640 x 480 (4:3) for playback.

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Answer 3

Oct 10, 2005 2:51 AM in response to Waymen

I'm happy to read that more people were having the same problem; I already posted in the DVDSP forum but nobody responded..

still I'm wondering, why does Quicktime scale to 720x540 instead of 768x567, the 4:3 standard related to d1/dv pixels. ?

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Answer 4

Oct 10, 2005 9:09 AM in response to Rick Roos

It scales it to make up the difference in pixel ratio between a monitor (square pixels) and a TV (rectangular pixels.)

I really wish you could tell it not to rescale it, but it doesn't look like you can.

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Answer 5

Waymen

Level 5

5,722 points

Oct 10, 2005 12:15 PM in response to Matt Davis

It's also a non-destructive scaling, no data is lost or converted, it's only rescaled for the display. If you want to change the display size to something else (from within the QuickTime Player) you can do that through the movie properties dialog or with an AppleScript (I have two scripts that I use for NTSC DV, one to display at 640 x 480 and another to go back to 720 x 480).

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Answer 6

Matt Davis Author

Level 1

30 points

Oct 10, 2005 1:58 PM in response to Rick Roos

Thanks to everyone who's chimed in with a reply - all appreciated by everyone, it seems!

I too wonder about the logic of squishing 576 to 540 lines to keep 720 horizontal lines. Shurely shome mishtake? That would fluff up the quality of the interlaced lines (and then some), whereas simply stretching the horizontal scale to 768 would lead to negligable loss of sharpness.

Ah well, at least with QT7 Pro we can resize it. 🙂

Thanks again!

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Answer 7

Waymen

Level 5

5,722 points

Oct 10, 2005 2:17 PM in response to Matt Davis

Ah well, at least with QT7 Pro we can resize it. 🙂

Actually, with QuickTime 7 I think the standard QuickTime Player allows you to resize.

If you don't have access to the movie properties dialog you can just hold down the shift key and drag the corner of the window frame to resize the movie, under QuickTime 7 the movie info dialog will be updated dynamically as you resize the movie.

In any case, you can use an AppleScript to set the display size with either the pro on non-pro player.

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Answer 8

Big Burro

Level 1

129 points

Oct 12, 2005 8:36 AM in response to Matt Davis

Don't you wish there was some utility to tell you what your clip real resolution is whether it's anamorphic or not, interlaced or not, etc? I was recently having serious problems importing 1080i demuxed clips into QT and FCP. Fighting some silent assumptions QT and FCP players were making all the way.

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Answer 9

Big Burro

Level 1

129 points

Oct 12, 2005 8:51 AM in response to Waymen

.. o converts NTSC's 720 x 480 to 640 x 480 (4:3) for playback ..

Depends, for file named *.dv I see 720X480 both for original and scaled
The same clip res-saved with extension .mov shows as 640 x 480 for scaled with keep original aspect ENABLED ?? Apple should stop monkeying behind the curtains too much.

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