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Cropping a video from 16:9 to 4:3

User avatar Ranko Kohime
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Cropping a video from 16:9 to 4:3

Wed Feb 05, 2014 9:10 am
I have a video that is 4:3, but it was recorded with pillarboxes in 16:9. I want to render it as 4:3, and cut off the pillarboxes, but when I set the project profile to a 4:3 setting, (HDV 1440x1080), and then apply a "Crop Scale & Position" effect to the video, I end up with a pillarboxed and letterboxed result.

I would have thought that cropping the video would work, but apparently not. What is the correct method for removing the pillarboxes?
capslock
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HDV 1440x1080 is 16:9 and stretches the pixels hozizontally by factor 1.33 (anamorphic pixels). I suggest (by guessing not probing) the following procedure: Create a 4:3 profile like 768x576 pixels (PAL 4:3 standard) and then use affine transition or pan, scan zoom effect to adjust the movie in the visible area.
User avatar Ranko Kohime
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capslock wrote:HDV 1440x1080 is 16:9 and stretches the pixels hozizontally by factor 1.33 (anamorphic pixels). I suggest (by guessing not probing) the following procedure: Create a 4:3 profile like 768x576 pixels (PAL 4:3 standard) and then use affine transition or pan, scan zoom effect to adjust the movie in the visible area.

Perhaps I should expatiate a bit. When I render the source video into that profile, (the source video is 1920x1080, BTW), the output file I get is 1440x1080, which is 4x3. The problem being that there's black all the way around the picture.

Specifically with that profile, I've used 4:3 source videos to render a 4:3 output before, so I'm not sure what you mean when you say that HDV 1440x1080 is a 16:9 format. ???
capslock
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To verify, please check specifications section at http://en.wikipedia.org/wiki/HDV
In HDV the pixel aspect ratio of 1440x1080 is 1,33 which results to 1920x1080 and that is 16:9. I assume the kdenlive preset is conform to the standard, but did not check that.

Your calculation giving an aspect ratio of 4:3 is correct with a pixel aspect ratio of 1 - which is not part of the HDV spec for 1080i.
ttguy
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Re: Cropping a video from 16:9 to 4:3

Fri Feb 07, 2014 10:53 pm
What can also confound these issues is the playback device you use to watch the output file. If the play back device does not automatically detect that the file is anamorphic then you can get results that apparently don't look right but might look fine when played back on a different device. eg you might get a 4:3 thin-o-vision on a software player but the same file will look fine played on a 16:9 TV via a DVD player.
In a similar vein you might want to look at the TV settings and how it is set up to play 4:3 vs 16:9 footage.
Idealy I would think you want you output file to be in a 4:3 format. And then the players should know what to do with it. A DVD player and your 16:9 TV should see it as 4:3 material and play it back with pillar bars on the side.
User avatar Ranko Kohime
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Re: Cropping a video from 16:9 to 4:3

Sat Feb 08, 2014 10:10 am
capslock wrote:To verify, please check specifications section at http://en.wikipedia.org/wiki/HDV
In HDV the pixel aspect ratio of 1440x1080 is 1,33 which results to 1920x1080 and that is 16:9. I assume the kdenlive preset is conform to the standard, but did not check that.

Your calculation giving an aspect ratio of 4:3 is correct with a pixel aspect ratio of 1 - which is not part of the HDV spec for 1080i.

The pixel aspect ratio is something I hadn't even considered (and why does something so superfluous exist?), but I checked the profile for HDV 1440x1080, and the PAR is indeed set to 1.0, so the preset does NOT conform to the standard.

Trying your suggestion also gave no results: the zoom effect doesn't affect the video, and even in 768x576 I end up with pillar and letterboxes. :(
ttguy
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"(and why doessomething [pixel aspect ratio] so superfluous exist?"
History of TV broadcasting and the invention of the wide screen TV.
http://en.wikipedia.org/wiki/Anamorphic_widescreen
" to allow widescreen material to be stored on formats or broadcast on systems that assume a non-widescreen aspect ratio"
User avatar Ranko Kohime
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ttguy wrote:Idealy I would think you want you output file to be in a 4:3 format. And then the players should know what to do with it. A DVD player and your 16:9 TV should see it as 4:3 material and play it back with pillar bars on the side.

That's exactly it. I'm implicitly trusting the end player to properly handle the aspect ratio.

The problem is that my source video already has the pillarboxes on it, ergo the raw video file is 16:9, yet only provides a 4:3 picture. My target audience is YouTube, so while perhaps most of them have 16:9 displays, some will still have 4:3 & 5:4 displays (I do, as my second monitor), and that's like a dagger in the heart of my OCD. :'(
capslock
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You will have to compromise - no format fits all screens, especially computer screens.
ttguy
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"The problem is that my source video already has the pillarboxes on it, ergo the raw video file is 16:9, yet only provides a 4:3 picture."
Then you should crop it and render it to a 4:3 format video and then let the play back device and youtube deal with it.
User avatar Ranko Kohime
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ttguy wrote:"The problem is that my source video already has the pillarboxes on it, ergo the raw video file is 16:9, yet only provides a 4:3 picture."
Then you should crop it and render it to a 4:3 format video and then let the play back device and youtube deal with it.

That's exactly what I've been beating my head against the wall trying to do. ;)
User avatar TheDiveO
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Ranko, how exactly do you crop your source footage? From rereading this thread I couldn't find out.


TheDiveO on YouTube: diving videos and aerial (quadcopter) videos, all made with Kdenlive.
TheDiveO Blog: know-how about Protune-grading in Kdenlive, GoPro HD Hero 3, DJI Phantom Quadcopter, full face mask diving, and some more...
User avatar Ranko Kohime
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TheDiveO wrote:Ranko, how exactly do you crop your source footage? From rereading this thread I couldn't find out.

I've tried "Crop, Scale and Position", and "Edge Crop".
User avatar TheDiveO
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Would be using the affine transition an option, where you scale and center the source clip such that you fill out the 4:3 output format with parts being outside getting clipped automatically during rendering? Just an idea...


TheDiveO on YouTube: diving videos and aerial (quadcopter) videos, all made with Kdenlive.
TheDiveO Blog: know-how about Protune-grading in Kdenlive, GoPro HD Hero 3, DJI Phantom Quadcopter, full face mask diving, and some more...

 
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