drokeby

Q: Why is spatial conform of 4k footage so soft?

I am editing 4k (actually UHD) footage (from a GH4) on a 1080p timeline in the most recent version of FCPX. The conformed video is unexpectedly soft. I wrote a small program to do a simple quarter scaling that averaged the values of each group of 4 pixels to produce a 1920 x 1080 result from 3840 x 2160 which resulted in a much superior result. I am assuming FCPX is using a more complex algorithm like perhaps a Lanczos scaling method for rescaling, and perhaps that is better for non-integral rescaling, but in this soon to be pretty important usage, the result is very much inferior. Is there a hidden option to change the rescaling algorithm in FCPX? Does anyone know whether there is a workaround, like making a Motion FCPX effect to do the rescaling?

 

If not, this significantly cripples FCPX in comparison to Premiere which seems to provide the crisper downscaling of 4K that I saw also in my simple bit of code

 

Thanks

 

David Rokeby

Final Cut Pro X, OS X Mavericks (10.9.4)

Posted on Jul 31, 2014 8:10 PM

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Q: Why is spatial conform of 4k footage so soft?

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  • by Snapper Paul,

    Snapper Paul Snapper Paul Aug 8, 2014 1:39 AM in response to drokeby
    Level 1 (0 points)
    Aug 8, 2014 1:39 AM in response to drokeby

    I agree - just doing a quick edit for a client to see some rushes and noticed that the 1080p output from FCPX is very soft. I was worried so went back and checked the raw footage and it's pin, so something's going on in the conversion, or I'm missing something. It's really almost unusable, so I'm hoping it's my fault

     

    Only solution so far is to sharpen in Compressor, but far from ideal as it screws up titles and other graphics.

     

    I always export timeline as ProRes before compressing by the way...

     

    Paul

  • by Russ H,

    Russ H Russ H Aug 8, 2014 5:51 AM in response to Snapper Paul
    Level 7 (21,825 points)
    Quicktime
    Aug 8, 2014 5:51 AM in response to Snapper Paul

    Snapper Paul wrote:

     

    I always export timeline as ProRes before compressing by the way...

     

    Have you tried transcoding some of the original media clips to Pro Res and then dropping those into a 1080 timeline?

     

    Russ

  • by drokeby,

    drokeby drokeby Aug 8, 2014 7:12 AM in response to Russ H
    Level 1 (1 points)
    Aug 8, 2014 7:12 AM in response to Russ H

    I will try this, but this will massively increase storage requirements. The 4k Prores files are going to be really big. Since there is no technical reason why the image cannot be as sharp as my dead-simple bit of code, I am hoping for a better solution!.

     

    To see the example where I compare the FCPX spatial conformance to a simple averaging of every square group of 4 pixels see: https://vimeo.com/102328743

  • by drokeby,

    drokeby drokeby Aug 8, 2014 7:17 AM in response to Snapper Paul
    Level 1 (1 points)
    Aug 8, 2014 7:17 AM in response to Snapper Paul

    There is a tool called GH444, with a GUI app called  GH444 GUI that will take gh4 footage and convert the 4K 8-bit 4:2:0 footage and output 1080p quasi 10-bit 422. The output is a series of dpx stills so it needs to be reconstructed into a movie again but it provides equivalent sharpness to my bit of rough code. You can find it here:

     

    Links to both the command line tool and the GUI (that work together) are accessed from here:

     

    http://www.eoshd.com/comments/topic/5426-mac-app-to-resample-gh4-8-bit-420-to-10 -bit-444/

     

    David

  • by drokeby,

    drokeby drokeby Aug 8, 2014 7:18 AM in response to Russ H
    Level 1 (1 points)
    Aug 8, 2014 7:18 AM in response to Russ H

    I forgot to mention that to really see the full difference, you need to download the original clip from the downloads section of the vimeo page. You can see the difference in vimeo, but it is much clearer with the original...

     

    David

  • by David M Brewer,

    David M Brewer David M Brewer Aug 8, 2014 7:19 AM in response to drokeby
    Level 6 (9,419 points)
    Video
    Aug 8, 2014 7:19 AM in response to drokeby

    Use Compressor to rescale your clips to 1080p...

  • by Tom Wolsky,

    Tom Wolsky Tom Wolsky Aug 8, 2014 7:31 AM in response to drokeby
    Level 10 (118,302 points)
    Apple TV
    Aug 8, 2014 7:31 AM in response to drokeby

    The frame rate is 30fps. Did you mean it to be that?

  • by David M Brewer,

    David M Brewer David M Brewer Aug 8, 2014 7:49 AM in response to Tom Wolsky
    Level 6 (9,419 points)
    Video
    Aug 8, 2014 7:49 AM in response to Tom Wolsky

    I don't know if you can see the difference in the photo...

     

    4k to 1080p2.jpg

    The left image is softer and lacks a little color compared to the image on the right. I've made Blue-ray discs from 4k footage. It's night and day when using Compressor to resize the footage compared to letting FCP X resize the video.

  • by Russ H,

    Russ H Russ H Aug 8, 2014 8:02 AM in response to David M Brewer
    Level 7 (21,825 points)
    Quicktime
    Aug 8, 2014 8:02 AM in response to David M Brewer

    David, FWIW, to my eye the color difference is pretty clear. But I have to look pretty hard to see the softness that you cite.

     

    When I downscale a complex 4K scene in FCPX and play the exported file, it looks very good.

     

    But no doubt you're correct that Compressor will typically do a better job of it.

     

    Ruas

  • by drokeby,

    drokeby drokeby Aug 8, 2014 10:30 AM in response to David M Brewer
    Level 1 (1 points)
    Aug 8, 2014 10:30 AM in response to David M Brewer

    Yes, I could do that. I will check the quality. It seems like a totally unnecessary step...

     

    David

  • by drokeby,

    drokeby drokeby Aug 8, 2014 10:32 AM in response to Tom Wolsky
    Level 1 (1 points)
    Aug 8, 2014 10:32 AM in response to Tom Wolsky

    The footage was shot UHD at 29.97, and I think the timeline is 30 fps. Are you suggesting that the time conform could be responsible for the softness?

     

    David

  • by drokeby,

    drokeby drokeby Aug 11, 2014 7:24 AM in response to David M Brewer
    Level 1 (1 points)
    Aug 11, 2014 7:24 AM in response to David M Brewer

    I tried doing the UHD to HD scaling in Compressor with linear interpolation and have pretty much exactly the same softness as in FCPX. I don't want nearest neighbour resampling as that just dumps 3 of the 4 pixels of the UHD. I also made sure that my timeline this time is 29.97, same as the source so that time-conform was not getting involved in any way.

     

    Some people have said that their GH4 4K is sharp in 1080p timelines in FCPX, but I have not seen any samples of this. Perhaps someone can upload a very short original 4K file and the 1080p timeline export showing good sharpness, and I will reprocess the file on my computer to see if there is variance in the way FCP scales on different machines.

     

    I suspect that we are never seeing anywhere near the optimal sharpness in UHD to HD in FCPX. The one positive is that the FCPX down-convert softening does reduce noise more than simple linear averaging of 4 neighbouring pixels.

     

    Anyone up to uploading a 4K and HD sample for me to test?

  • by Richardttt,

    Richardttt Richardttt Aug 11, 2014 5:19 PM in response to drokeby
    Level 2 (165 points)
    Aug 11, 2014 5:19 PM in response to drokeby

    I've been shooting 4K with the GH4 and placing the footage in a 1920x1080P 24fps timeline and haven't really noticed any softness issues. See if you see any issues with the videos below. Now I haven't done a frame by frame or scopes comparison.

     

    Here are two recent videos that I shot:

     

    https://www.youtube.com/watch?v=53oOZDQ4DS4

     

    https://www.youtube.com/watch?v=dw4dgDv9RCE

     

    Richard Taylor

  • by drokeby,

    drokeby drokeby Aug 12, 2014 7:58 AM in response to Richardttt
    Level 1 (1 points)
    Aug 12, 2014 7:58 AM in response to Richardttt

    Thanks for this, but it is impossible to tell about sharpness of 4k to HD in a 720p movie... The issue I am talking about has to do with the fact that you can downscale 4K to HD with excellent sharpness, but in FCPX it is significantly less sharp. It is still way sharper than 720p, and comparable to most 1080p footage in terms of sharpness, but a significant notch down from 4K downscaled in Premier or by simple averaging.

     

    David

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