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Green border lines appearing after compression

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Pete Nicholson
Green border lines appearing after compression
on Apr 26, 2010 at 12:38:25 pm

Hi there,

I'm using FCP 7 and am trying to compress a short video for uploading to vimeo. I followed the vimeo compression guidelines for DV widescreen (compressed at 854 by 480) and compressed the file. Here are the full compression settings:

File Extension: mov
Estimated size: 1.29 GB/hour of source
Audio Encoder
AAC, Stereo (L R), 44.100 kHz
Video Encoder
Format: QT
Width: 853
Height: 480
Pixel aspect ratio: Square
Crop to: Center crop for 1.778:1
Padding: None
Frame rate: 30
Frame Controls: Off
Codec Type: H.264
Multi-pass: On, frame reorder: On
Pixel depth: 24
Spatial quality: 75
Min. Spatial quality: 50
Key frame interval: 60
Temporal quality: 50
Min. temporal quality: 50
Average data rate: 3.072 (Mbps)
Fast Start: on

It all looks good except for one strange thing: on the left and right hand side borders of the compressed video, there are fluorescent green lines running from top to bottom.

<a href='http://i1.creativecow.net/u/174138/fcp-forum-pic.jpg'><img src='//i1.creativecow.net/u/174138/fcp-forum-pic.jpg' border='0'></a>

The lines are visible in VLC, but not in Quicktime. So I tried to upload the video to vimeo to see if they appear, and they do. They're not very noticeable, but I'd love to get rid of them.

Does anybody have any ideas?


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Pete Nicholson
Re: Green border lines appearing after compression
on Apr 26, 2010 at 1:23:42 pm

I should add that when I export a full quality version directly from FCP, the lines don't appear. And also that this is my first post, and I was unable to find any mention of this problem in existing threads, and I'm very grateful for any help!


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Rafael Amador
Re: Green border lines appearing after compression
on Apr 26, 2010 at 4:16:58 pm

[Pete Nicholson] "I should add that when I export a full quality version directly from FC , the lines don't appear"
Pete,
What do you mean by full quality?
Uncompressed?
If so, is normal. .
Compressed formats use blocks. Uncompressed is not based in macro-blocks.
By default, tray to avoid odd numbers of lines.
Rafael



http://www.nagavideo.com


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Rafael Amador
Re: Green border lines appearing after compression
on Apr 26, 2010 at 3:14:07 pm

Vimeo recommended you a size, but you set a different one.
You set 853 pixels instead of 854.
Compression formats uses blocks of pixels.
The left most line is out of any macro block, so doesn't get properly compressed.
Up to Wikipedia; "Variable block-size motion compensation (VBSMC) with block sizes as large as 16×16 and as small as 4×4,".
Up to this, the size recommended by Vimeo is also wrong.
Try 852 x 480.
rafael


http://www.nagavideo.com


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Pete Nicholson
Re: Green border lines appearing after compression
on Apr 26, 2010 at 4:14:47 pm

Thanks so much Rafael! 852 made the line bigger, but 854 got rid of it completely. Thanks again.


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Rafael Amador
Re: Green border lines appearing after compression
on Apr 27, 2010 at 4:25:16 pm

Yes.
I really don't know how did I calculate 852.
Obviously the number is wrong is not a multiplier of 4.
854 it is.
rafael

http://www.nagavideo.com


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Rafael Amador
Re: Green border lines appearing after compression
on Apr 27, 2010 at 4:30:29 pm

Sorry again.
In fact is 852 the number that should work: 852/4= 213
854/4= 213,25
But if the green line disappeared, everything is OK.
Rafael

http://www.nagavideo.com


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