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 Post subject: Subtitle Removal
PostPosted: Wed Mar 06, 2013 7:46 pm 
Coppermine
Coppermine

Joined: Mon Oct 12, 2009 4:47 am
Posts: 687
I think I know the answer but.....is there ANY way to remove, I guess one would say 'hard coded' subtitles from an .avi file? I believe anything is possible and I am assuming someone somewhere has done this before.


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 Post subject: Re: Subtitle Removal
PostPosted: Wed Mar 06, 2013 8:54 pm 
Smithfield
Smithfield

Joined: Sun Jun 18, 2006 7:37 pm
Posts: 5393
No, because it's part of the image.


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 Post subject: Re: Subtitle Removal
PostPosted: Fri Mar 08, 2013 6:19 am 
Smithfield
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The only thing I can think of is if the captions are low enough in the frame that you could crop the video and remove them that way.

Obviously you're going to lose some of the picture but it sounds like you're willing to try anything.


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 Post subject: Re: Subtitle Removal
PostPosted: Sat Mar 09, 2013 4:31 am 
Coppermine
Coppermine

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That's not a bad idea, Satch. I guess it would work only for certain shows for obvious reasons. I'm just surprised no one has been able to remove hard coded subs yet.

I was able to edit some things using an .mkv editing tool. I could remove subs when they were srt files so I was really hoping someone could remove the hard coded subs.


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 Post subject: Re: Subtitle Removal
PostPosted: Sat Mar 09, 2013 6:19 am 
Smithfield
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Removing srt subtitles is possible because they are overlayed on top of the video. The picture information is still there to be revealed once the captions are removed.

With hard coded captions you lose the picture detail so a simple removal is not possible since whatever was underneath them is gone.


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 Post subject: Re: Subtitle Removal
PostPosted: Sat Mar 09, 2013 10:06 am 
Smithfield
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robertco300 wrote:
I'm just surprised no one has been able to remove hard coded subs yet.

Because it's part of the image. You could remove them, but then what? You don't know what those pixels were originally and you're left with a silhouette of the text.

I mean, if it's something like this:
Image
Then sure, cropping would work.

But if it's something like this:
Image
How are you going to get rid of those without making it look conspicuous? In addition, if it's for a feature length film or similar, are you going to sit down and use Photoshop on possibly over 100,000 frames?


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 Post subject: Re: Subtitle Removal
PostPosted: Mon Mar 11, 2013 3:43 am 
Smithfield
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I wonder if an algorithm could be made that compares sequential frames of a video and extrapolates or even cut and pastes the missing picture elements that the captions are covering?

Obviously it wouldn't be perfect but it could possibly do a decent enough job.


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 Post subject: Re: Subtitle Removal
PostPosted: Mon Mar 11, 2013 5:41 am 
Smithfield
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I thought about that too, but you'd have to consider if the I-frame you want to use as a reference frame is clean and you'd have to predict the motion of the pixels, which for all intents and purposes, is probably close to impossible.


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 Post subject: Re: Subtitle Removal
PostPosted: Mon Mar 11, 2013 7:54 am 
Smithfield
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I don't think it would be that hard to predict pixel locations. Over several frames you could theoretically track groups of pixels and plot their tragectories and fill them in where the captions covered them up.

If you ever witnessed a quick signal drop in digital over the air TV you'll see some kind of pixel tracking is going on already in the tuner's algorithm.

Even if the frames are still the constant changing of captions will, over time, reveal most of the scene. So the algorithm could work backwards to fill in the missing picture. This is true even if the frames are in motion.

Edit: I was also thinking of Adobe's context aware fill they have for Photoshop and wondered about a video version. It looks like someone is working on that. http://vimeo.com/44434878

I think this could do the trick.


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 Post subject: Re: Subtitle Removal
PostPosted: Mon Mar 11, 2013 8:13 am 
Smithfield
Smithfield

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The pixel tracking is from the P-frames or B-frames. The signal doesn't clean up until it gets another I-frame. You can do the same thing in VLC or MPC if you skip around.

It also slipped my mind that Adobe had that feature. I'm sure it'll work, but the problem is that motion vectors aren't preserved in subtitles so you would still have to run it on every frame to guess what each frame is supposed to be, then re-encode it. I suppose you could do it on the fly with GPU acceleration, depending on how fast the content aware algorithm fill is.


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 Post subject: Re: Subtitle Removal
PostPosted: Mon Mar 11, 2013 9:28 am 
Smithfield
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I wasn't thinking that this was doable on the fly but rather editing the file then playing it back after.


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 Post subject: Re: Subtitle Removal
PostPosted: Mon Mar 11, 2013 10:45 am 
Smithfield
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I think it's more worthwhile to do it on the fly for efficiency's sake. Render the frame, run the content aware fill. It's like that "Karaoke Filter" Realtek sound chips come with.


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