How to eliminate a news crawler or other unwanted object
Posted: Sat Oct 20, 2012 4:13 pm
Suppose you have a video with a news crawl trailer near the bottom of the screen that you want to get rid of. You can crop the bottom of the screen to remove that part. That can be done in the video resize editor. The ConvertXtoDVD v5 editor is shown here but the one in other VSO programs is similar and requires the same steps.
An example is shown in Image 1 that is not typical but serves to illustrate the procedure to use. Image 2 shows what it looks like after the trailer is cropped out. Notice the distortion of the square and circle there. Another step is needed to fix that distortion.
The simplest way is to pad the top by the same amount as that used to crop the bottom -- 40 pixels in this example. But that adds a black bar at the top as in image 3 which does not look good. A better approach is to split the padding equally between top and bottom, as if letterboxed, which produces two smaller black bars 20 pixels high and looks better.
If you don't want the black bar(s), you will have to crop the sides, again in order to prevent distortion. Cropping the sides will lose part of your picture naturally.
There are two ways to do that. Check Symmetric Pad/Crop before proceeding.
The simplest way is to use the slider to adjust the preview until you find a scene with something round or square that you can judge distortion of. Then start increasing cropping of the sides until you think distortion is eliminated.
The most precise way is to use equations in http://forums.vso-software.fr/calculati ... t9319.html to predict how much should be cropped from the sides. For the video used in this example, both sides should be cropped by 40 pixels to eliminate distortion introduced by cropping the bottom 40 pixels as shown in Image 4.
Note that the need for the same amount of cropping of each side as done on the bottom is purely coincidental and specific to the video used in this example. That will rarely happen for most videos. And note that the total amount cropped from the sides is double that cropped from the bottom anyway.
An example is shown in Image 1 that is not typical but serves to illustrate the procedure to use. Image 2 shows what it looks like after the trailer is cropped out. Notice the distortion of the square and circle there. Another step is needed to fix that distortion.
The simplest way is to pad the top by the same amount as that used to crop the bottom -- 40 pixels in this example. But that adds a black bar at the top as in image 3 which does not look good. A better approach is to split the padding equally between top and bottom, as if letterboxed, which produces two smaller black bars 20 pixels high and looks better.
If you don't want the black bar(s), you will have to crop the sides, again in order to prevent distortion. Cropping the sides will lose part of your picture naturally.
There are two ways to do that. Check Symmetric Pad/Crop before proceeding.
The simplest way is to use the slider to adjust the preview until you find a scene with something round or square that you can judge distortion of. Then start increasing cropping of the sides until you think distortion is eliminated.
The most precise way is to use equations in http://forums.vso-software.fr/calculati ... t9319.html to predict how much should be cropped from the sides. For the video used in this example, both sides should be cropped by 40 pixels to eliminate distortion introduced by cropping the bottom 40 pixels as shown in Image 4.
Note that the need for the same amount of cropping of each side as done on the bottom is purely coincidental and specific to the video used in this example. That will rarely happen for most videos. And note that the total amount cropped from the sides is double that cropped from the bottom anyway.
