keefwaddo

Q: VERY strange compression artifacts

My most recent project. If the video begins with with a slug (over which I put the titles) or even a fade to colour transition, the following clips have strong compassion artifacts. If I remove the slug/transition, the video is perfect.

 

I have never seen anything like this before. There is a zip file linked with two short clips, with and without the transition at the start.

 

Any ideas?

 

Cheers

 

Waddo

 

test

final cut pro x, Mac OS X (10.6.7)

Posted on Feb 25, 2016 3:42 PM

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Q: VERY strange compression artifacts

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  • by Tom Wolsky,

    Tom Wolsky Tom Wolsky Feb 25, 2016 4:36 PM in response to keefwaddo
    Level 10 (118,107 points)
    Apple TV
    Feb 25, 2016 4:36 PM in response to keefwaddo

    Incredibly difficult material to compress, especially for a long GOP like MPEG-4 using H.264. You'll have to up the data rate substantially especially for a 1080 file.

  • by keefwaddo,

    keefwaddo keefwaddo Feb 25, 2016 5:40 PM in response to Tom Wolsky
    Level 1 (8 points)
    Photos for Mac
    Feb 25, 2016 5:40 PM in response to Tom Wolsky

    Thanks for the reply.

     

    The thing is, the same clip without the transition at the start compresses fine with no artefacts. So although the foliage is tricky to compress cleanly, this is not the issue here. It is putting a slug or transition at the start that causes this anomaly.

     

    Waddo

  • by Tom Wolsky,

    Tom Wolsky Tom Wolsky Feb 25, 2016 5:51 PM in response to keefwaddo
    Level 10 (118,107 points)
    Apple TV
    Feb 25, 2016 5:51 PM in response to keefwaddo

    YYou do see the artifacts even without the transition, but the fade transition makes it hugely more difficult because no two adjacent frames are identical. The moving leaves makes that impossible, together with the fade, do by the time you get to the need of the long GOP the frames are a mess.

  • by keefwaddo,

    keefwaddo keefwaddo Feb 25, 2016 7:13 PM in response to Tom Wolsky
    Level 1 (8 points)
    Photos for Mac
    Feb 25, 2016 7:13 PM in response to Tom Wolsky

    Again thanks for the reply.

     

    Have made another sample.

    test 2

    This time I added a different 1st clip and changed the start to a slug rather than transition. Now the tree shot is the second clip with no transition. Still the artefacts are there. In the second file the slug was removed and there are no artifacts. So now we can see this is not about the transition because there is only a slug.

     

    I have rearranged clips many times, thinking it was a problem specific to certain clips; but if the video starts with a slug or transition the artefacts always show.

     

    Waddo

  • by Tom Wolsky,

    Tom Wolsky Tom Wolsky Feb 25, 2016 7:31 PM in response to keefwaddo
    Level 10 (118,107 points)
    Apple TV
    Feb 25, 2016 7:31 PM in response to keefwaddo

    OOnce again that video is never going to look good in a GOP structure format at 1080 unless you increase the data rate, and even then it's going to be marginal quality at best.

  • by keefwaddo,

    keefwaddo keefwaddo Feb 25, 2016 7:38 PM in response to Tom Wolsky
    Level 1 (8 points)
    Photos for Mac
    Feb 25, 2016 7:38 PM in response to Tom Wolsky

    Actually the video looks fine in the sample with no slug.

     

    I have many videos on my site and they are all fine. Only here, by adding a slug at the start, do I get strange artifacts. The main problem is I want the slug so I can use my standard titles with black background, otherwise they have to be superimposed on actual video footage.

     

    These seem to be compression artefacts but they only appear when the video starts with a slug. remove the slug and the video is fine. This I have never experienced before.

     

    Waddo

  • by Tom Wolsky,

    Tom Wolsky Tom Wolsky Feb 25, 2016 10:03 PM in response to keefwaddo
    Level 10 (118,107 points)
    Apple TV
    Feb 25, 2016 10:03 PM in response to keefwaddo

    IIt's actually not fine; it's just not so noticeable.  Best of luck with your projects.