Quantcast How to best perform overscan correction? - digitalFAQ Forum
  #1  
02-19-2010, 07:52 PM
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I have a question: I've looked here, but couldn't find anything specific...Could you describe how to remove too much overscan from a video file?

The attached image (from a .vob file) isn't necessarily a mistake...That's the frame you get from an older telecine. I would like to know which program (freeware, if available) could crop (correct?) the too-large area of overscan present, so that a more correct appearing 720/704x540 sized frame is seen?

If you could at all possibly carve out the time for it, step-by-step instructions would help the absolute most...I simply can NOT get the hang of Virtual Dub, for example.

I want to learn more about picking the right program for the right "problem"...Just like having the right tool in the toolbox when something breaks and needs fixing...

Just like always, I thank you on behalf of myself and fellow-forum members in advance!

overscan.overkill.jpg


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  #2  
02-19-2010, 08:38 PM
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Is this an interlaced video? From VHS, for example.
Or is this an actual film dump, with progressive frames?

You have to resize, but it has to be progressive first. This means deinterlacing, if require, using a good method (which I'll explain).

If you can upload a sample clip from the VOB, I can create a VirtualDub VCF file that you can just open, with the filters preset. You can learn both from my step-by-step instructions AND by reverse engineering and viewing the settings on your own computer.

There are several methods to do this -- and VirtualDub is the easiest and fastest method. (Also the only really free method.)

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  #3  
02-19-2010, 09:08 PM
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signal chain:

16mm
video camera pickup on telecine
DVD recorder hard drive

file is interlaced.

BTW: I meant to type 720/704x480 above, oops...

Let me know if I need to provide more detail?


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File Type: mpg onion.mpg (6.27 MB, 5 downloads)
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  #4  
02-21-2010, 11:20 PM
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Several things have to be done here.

First, deinterlace the video with a good method. You cannot resize an interlaced video very well. Using VirtualDub, two easy-but decent options exist: Yadif (built into VirtualDub 1.9.x), or Deinterlace Area-Based. While some purest would insist Yadif must look better, it's not always the case -- try both. I used Area-Based on the test clip.

Next, you have to upscale the image, by cropping off the sides. Remember that your input is 720x480. That's a ratio of 3:2 (240x3=720 x 240x2=480), so we want to cut off 3x2. For example, 15 pixels from left/right, 10 from top/bottom. That won't be enough here, but you get the idea now. For the image you showed, I used 100+66 (50 L/R, 33 T/B). In VirtualDub, you pick the resize filter, resize to 720x480, and the go to the cropping options and cut off your pixels.

So now your image is dominant on-screen, not a small distant-looking box .

If you want to further mask that overcan to a clean box-like shape, you again run a resize filter, but this time you pick the letterbox/masking option, and set it to 720x480. Then enter the cropping and chop pixels off all sides. 3:2 is suggested, but not required. For TV overscans, the left/right loses more than top/bottom. About 16 off L/R (16L,16R) and 8 off T/B (8T,8B) is good. For your example, I think I did 22 L/R and 12 T/B -- and it should still be fine on a TV, not show borders. Note that preview doesn't always work here, just wait for the "full preview" in the output window of VrtualDub. VirtualDub has a bug with plugin-view preview (in crop mode), when you stack resize filters.

Remember that your video is now progressive. I suggest leaving it as such, don't re-encode it to bottom-field MPEG-2.

The VCF file, sample MPEG, screen shots of working in VirtualDub -- that will come soon. Just can't get to it right now, wanted to give you the text-only version for now.

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  #5  
02-25-2010, 03:09 PM
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Can I successfully use both progressive and interlaced assets in one DVD presentation?
Or should all the attributes of each file used in a single disc creation 'match'??

I ask, because:

1. Already been 'down the road' with what all-in-one editing, etc. programs do with 'mixed' content files for inclusion on one disc...
2. Already seen the butcher job one specific editing + encoding program does with a file if you dare try to employ any filter...

...And have ended up completely unsatisfied with the results...*sigh*
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02-25-2010, 09:08 PM
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Interlaced and progressive content can exist on the same DVD, yes. Most software will place the different types of MPEGs in separate VTS. If you're not sure what that means, multiple VTS for DVD authoring is explained on the authoring intro guide: http://www.digitalfaq.com/guides/vid...uthor-burn.htm

This is one reason I use Ulead DVD Workshop 2 for authoring -- it does multi VTS quite well.
It's only $49 from B&H right now, a steal. (Use this link if you buy it.)

If you want to see a real mess, get a live DISH Network or DirecTV stream. Not a capture of one, but the actual beamed-from-satellite stream. Working with those files takes video voodoo -- they're all kinds of messed up, with interlace and progressive mixed, 24p and 30i mixed.

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  #7  
02-27-2010, 05:51 PM
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Which is the most correct version of VirtualDub that I should obtain/be using? I am, at almost ALL times, working with mpeg-2 files sized at 704/720x480...

I would like to practice 'easier' filtering tasks while I await more detailed instructions from you on how best to crop/remove the overkill masking around the "small distant-looking box".
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  #8  
02-27-2010, 06:18 PM
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This one: http://www.digitalfaq.com/forum/show...-pre-1727.html

Easy, huh?

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  #9  
02-27-2010, 06:23 PM
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the bomb. The absolute BOMB of all prior bombs.
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