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| spl1tscreen |
 Posted: Jun 26 2014, 06:27 PM |
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Newbie
Group: Members
Posts: 2
Member No.: 38114
Joined: 26-June 14
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Hi guys,
As the title says, I'm trying to crop a video from the recorded 640 x 480 to a 150 x 150 region of interest. However, when I do this, I get a very distorted video with a repeated diagonal line down the centre; like this: http://i.imgur.com/VLV0VgB.jpg. Now I suspect this is because I go from a rectangular to square view. Indeed, when I crop the video at close to the same ratio (200 x 150) I end up with just one diagonal line going from top left to bottom right.
Here are the file details:
Video:
Frame size, fps (µs per frame): 640x480, 15.000 fps (66666 µs)
Length: 31498 frames (34:59.84)
Decompressor: Internal Motion JPEG decoder (MJPG)
Number of key frames: 31498
Min/avg/max/total key frame size: 26516/27848/29824 (856604K)
Min/avg/max/total delta size: (no delta frames)
Data rate: 3342 kbps (0.09% overhead)
Here is the process I use to crop the video:
1) Video - Filters
2) Add...
3) null transform
4) Cropping...
5) Play about with offsets
6) OK, then save as avi
I'm using VirtualDub 1.10.4. |
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| Abrazo |
| Posted: Jun 26 2014, 07:04 PM |
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Advanced Member
Group: Members
Posts: 775
Member No.: 28995
Joined: 5-November 10
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The problem comes from the non-codec friendly size of your destination file.
Instead of using the "null transform" filter, you can better use the "resize" filter.
New size : select "Absolute" and introduce the pixels in width (and the height should automatically adapt based on what you select in the next setting).
Aspect ratio : select "Same as source"
Filter mode : "Lanczos3"
Interlaced: not checked
Framing options: Select Letterbox and introduce an identical width and height if you like to.
Codec-friendly sizing: to really be sure that you will not get a diagonal as a result, select "Multiples of 8 (or 16)" at preference.
(You will see that the size will change from 150x150 to 144x144.
Via the "resize" filter you can also apply "Cropping" if you like to.
(via Video > Filters... > click once on the resize filter, and click the "Cropping"-button. |
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| raffriff42 |
| Posted: Jun 26 2014, 09:30 PM |
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Advanced Member
Group: Members
Posts: 384
Member No.: 35081
Joined: 25-June 12
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If you are not resizing, but only cropping, set size = "relative, 100%", but otherwise follow Abrazo's advice. You can keep your null filter and add a Resize filter below it, or do your cropping within the Resize filter. |
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| spl1tscreen |
| Posted: Jun 29 2014, 09:15 PM |
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Newbie
Group: Members
Posts: 2
Member No.: 38114
Joined: 26-June 14
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Thank you both for your replies. This is exactly what I needed.
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