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Crop your Videos to a certain Aspect Ratio

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Posted by: Shiv Kumar Views: 1127   Favorited: 0 Comments: 1
August 18, 2008 07:01 PM
Filed Under:  How To, New Feature
Tags:  Aspect Ratio, CinemaScope, Letterboxing, Video Encoding
This article pertains to the Crop To Aspect feature ExposureRoom members have available to them at the time of uploading their assets. Use this feature in order to remove Letterboxing from your videos. To be able to use this feature correctly, you MUST know the final aspect ratio you want your transcoded videos to be in. The value you provide in the Crop To Aspect box in the Upload Asset screen is the decimal number. For example:
 
HD Aspect Ratio
16:9 = 16/9 = 1.78 (Enter 1.78 for this case)
 
CinemaScope Aspect Ratio
2.35:1 = 2.35 (Enter 2.35 for this case)
 
Note: This feature does not apply to Pillar boxed videos. Please also note that your original video is not touched. Only the transcoded videos will be cropped.
 

Image 1: Screen shot showing the option for the new Crop To Aspect Feature
 

HD Videos Letterboxed to SD Aspect Ratio

This is one case where you might want to use this feature. Please note that this kind of thing can and should be “fixed” at the time of encoding your videos before uploading them to ExposureRoom. In order to learn how you can fix this issue at the time of encoding, please take a look at this article:
 
If you don’t have the original with you or for some reason you are not able to fix this issue at the time of encoding you can use this feature to remove the Letterboxing. Please take a look at Image2 and Image 3 below to get a sense of "before" and "after" to see if this feature applies to your video and if this is really what you want to do.
 
Image 2: Before - HD Video (16:9 Aspect ratio) in SD (4:3 Aspect ratio) with Letterboxing
 
Image 3: After - Video Cropped to HD Aspect ratio (16:9)
 

HD Aspect Video (16:9) Letterboxed to CinemaScope Aspect (2.35:1)

This is obviously an intentional choice you’ve made. You’ve shot your video within the confines of a CinemaScope frame and with the intent to letterbox your videos to produce a CinemaScope aspect picture. The video is still in the HD aspect ratio (16:9) but the picture (due to the letterboxing) is in CinemaScope aspect ratio (2.35:1). If this case applies to your video please take a look at Image 4 and Image 5 to get a sense of "before" and "after" to ensure you want to crop your video to the aspect ratio of your choice.
 
Image 4: Before  - HD Video (16:9 Aspect Ratio) Letterboxed to CinemaScope Aspect Ratio (2.35:1)
 
Image 5: After - HD Video Cropped to CinemaScope (2.35:1) Aspect Ratio
 
Once again, this is something you can do yourself, before uploading your video to ExposureRoom. However it typically involves one more encoding step which takes a bit more time than the original encode did. But this step could potentially reduce the quality of your final video unless you’re dead sure of what you’re doing. This feature was introduced so as to save you the time and headache in getting it right every time.
 

Cropping your Videos: Providing the Aspect Ratio Value

As you can imagine there are many different pieces of information we would need in order to be able to crop your videos just the way you’d want. Since we have the height and width of the original video you upload, we figured that the simplest way to ask you how you want your videos cropped is to ask for the aspect ratio you want the cropped version to be in.
 
This may present a problem to some of you still getting to grips with the math. So let’s get to the bottom of this last step. For this discussion we assume your video is 1280 pixels wide. If your video is really an HD video in SD aspect and you want it cropped to HD aspect, the Crop To Aspect value is simply 1.78. Please take a look at Image 6 below. Simply dived the width (1280) by the intended height (720) and you get 1.7777777777777778. Round that off to 1.78.
 

Image 6: How to get at the Crop Aspect Value
 
In order to crop to Cinemascope aspect you need to know the resulting height of the image in your video. We’ve found quite a few videos that are either already cropped or have letterboxes but the final height of the image varies, resulting in varying aspect ratios such as 2.35, 2.36, 2.37, 2.38. In order to get what you expect, please measure the image height of your video and then divide the width by the this height to arrive at the aspect ratio you should use.
 
Please note that an aspect ratio of 2.35:1 (or dimensions of 1280x544) is the ideal because the width and height are both divisible by 16 and video players (including Flash video) perform best when video dimensions are divisible by 16.

Comments



kim hyun moo    October 04, 2008 01:43 AM

HM MOVIE


KIM HYUN MOO



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