About Black Lines Or Left And Right Side Of DVD Video?

koronoru · Post by **koronoru** » Wed Oct 22, 2003 11:00 am

Taking this thread in a slightly different direction:

Most DVD video I've seen doesn't quite fill the 720x480 frame horizontally - there are black bars of 2 pixels on one side and 3 on the other. It's not really possible to remove them with a pure crop (no scaling) without losing video, because to do so would give me a non-multiple-of-8 width and screw up the encoding. I'd have to either cut out 8 pixels (including 3 of video) or leave the bars where they are.

My usual solution would be to just leave them alone - they aren't really hurting anything - but that proved to be a problem in a few shots in my current project (not yet posted) where I was using a negative video effect, because the effect applied to the entire frame including the black bars, turning them into obtrusive white bars. My solution was to crop the bars out and then add them back in (as pure black) before doing the encode.

Corran · Post by **Corran** » Wed Oct 22, 2003 7:43 pm

koronoru wrote:Taking this thread in a slightly different direction:

Most DVD video I've seen doesn't quite fill the 720x480 frame horizontally - there are black bars of 2 pixels on one side and 3 on the other. It's not really possible to remove them with a pure crop (no scaling) without losing video, because to do so would give me a non-multiple-of-8 width and screw up the encoding. I'd have to either cut out 8 pixels (including 3 of video) or leave the bars where they are.

My usual solution would be to just leave them alone - they aren't really hurting anything - but that proved to be a problem in a few shots in my current project (not yet posted) where I was using a negative video effect, because the effect applied to the entire frame including the black bars, turning them into obtrusive white bars. My solution was to crop the bars out and then add them back in (as pure black) before doing the encode.

I would sugest you look at avisynth also. Take a look in my previous post at the avisynth scripting. What those two lines lines are basically saying is to remove 6 pixels from the left and 6 from the right and then resize the video to a valid resolution divisible by 16.

In like 4 seconds not only have you removed black lines but you saved time not having to rerender an intermediate HQ source file that takes up space on your harddrive. Also you're cropping 4 pixels less from the video. This is because Avisynth can internally work with a video resolution in horizontal increments of 4 pixels hence 12 pixels of information gone instead of 16.

NicholasDWolfwood · Post by **NicholasDWolfwood** » Wed Oct 22, 2003 8:56 pm

AFAIK, he's not using Windows at all...he's using Linux.

koronoru · Post by **koronoru** » Thu Oct 23, 2003 1:03 pm

Corran Productions wrote:I would sugest you look at avisynth also. Take a look in my previous post at the avisynth scripting. What those two lines lines are basically saying is to remove 6 pixels from the left and 6 from the right and then resize the video to a valid resolution divisible by 16.

In like 4 seconds not only have you removed black lines but you saved time not having to rerender an intermediate HQ source file that takes up space on your harddrive. Also you're cropping 4 pixels less from the video. This is because Avisynth can internally work with a video resolution in horizontal increments of 4 pixels hence 12 pixels of information gone instead of 16.

As NDW said, I'm not using Windows - but what you describe wouldn't be an improvement over what I'm currently doing anyway. The software I'm using is capable of working in increments of one pixel internally - I crop the 720x480 down to 715x480, removing the black bars and not removing anything else. The only question, then, is what to do next - because it has to be a multiple of 8 in order for the encoder to work. I could rescale to 720x480, but that would change the aspect ratio (not by much, but I'm a perfectionist). Or I could put the black bars in - which is what I did. The software will do either; it's just a question of deciding which one is better. I don't need to create an intermediate file either way.

The reason I bother with cropping when I'm just going to put the black bars back in later anyway, is described in my previous post - I'm using a negative video effect which sometimes changes the black bars into white bars, and those are annoying. Cropping and then putting them back allows me to keep them black all the way through. When you watch the video full-screen they're invisible, and when you watch the video in the window it is, at least, no worse than the original DVD video which had the black bars to begin with.

Corran · Post by **Corran** » Thu Oct 23, 2003 3:23 pm

I didn't realize that you weren't using windows... hmmm. Is the someway then that you could use some sort of alpha/image matte in your video instead of cropping to get the bars out? That way they would be transparent. That would fix it right? I've never tried inverting something like that so I'm not sure but it seems to make sense to me.

koronoru · Post by **koronoru** » Mon Oct 27, 2003 12:51 pm

Corran Productions wrote:I didn't realize that you weren't using windows... hmmm. Is the someway then that you could use some sort of alpha/image matte in your video instead of cropping to get the bars out? That way they would be transparent. That would fix it right? I've never tried inverting something like that so I'm not sure but it seems to make sense to me.

Yes, I could do that, but why? It would be more work, and would produce exactly identical results.

Scintilla · Post by **Scintilla** » Mon Oct 27, 2003 4:55 pm

koronoru wrote:
Corran Productions wrote:I didn't realize that you weren't using windows... hmmm. Is the someway then that you could use some sort of alpha/image matte in your video instead of cropping to get the bars out? That way they would be transparent. That would fix it right? I've never tried inverting something like that so I'm not sure but it seems to make sense to me.
Yes, I could do that, but why? It would be more work, and would produce exactly identical results.

Well, if you only have to do it for the parts where you want to use the negative effect...

And besides, that way you wouldn't have to worry about all this cropping and slight quality loss from resizing.

koronoru · Post by **koronoru** » Mon Oct 27, 2003 5:07 pm

Scintilla wrote:And besides, that way you wouldn't have to worry about all this cropping and slight quality loss from resizing.

No quality loss - I'm not resizing - and the crop-out-bars and add-them-back operations are just command-line options to sosftware I'm already using. Perhaps you confused me with someone else on this thread who was doing more elaborate processing? It's not important, anyway.

Inuyasha666 · Post by **Inuyasha666** » Tue Oct 28, 2003 2:26 am

Scintilla wrote:
koronoru wrote:
Corran Productions wrote:I didn't realize that you weren't using windows... hmmm. Is the someway then that you could use some sort of alpha/image matte in your video instead of cropping to get the bars out? That way they would be transparent. That would fix it right? I've never tried inverting something like that so I'm not sure but it seems to make sense to me.
Yes, I could do that, but why? It would be more work, and would produce exactly identical results.
Well, if you only have to do it for the parts where you want to use the negative effect...

And besides, that way you wouldn't have to worry about all this cropping and slight quality loss from resizing.

U lose quality resizing to a smaller resolution? I kinda resized it to 704x480 when I was making the project file in DVD2AVI already cause I am using the negative effect with Adobe Premiere for one of my DBZ videos. Also, I wanted to get rid of the black bars and it got rid of it. At the final point of making my video I want my video be probably 352x240 resolution so I don't really know what u mean by losing quality from resizing, it looks the same to me.

Scintilla · Post by **Scintilla** » Tue Oct 28, 2003 12:31 pm

Inuyasha666 wrote:
Scintilla wrote:And besides, that way you wouldn't have to worry about all this cropping and slight quality loss from resizing.
U lose quality resizing to a smaller resolution? I kinda resized it to 704x480 when I was making the project file in DVD2AVI already cause I am using the negative effect with Adobe Premiere for one of my DBZ videos. Also, I wanted to get rid of the black bars and it got rid of it. At the final point of making my video I want my video be probably 352x240 resolution so I don't really know what u mean by losing quality from resizing, it looks the same to me.

I meant resizing back up from the cropped version to a full 720x480. I thought I had seen that mentioned somewhere in this thread...