Why is spatial conform of 4k footage so soft?

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Level 1

7 points

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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Answer 1

May 9, 2017 5:48 PM in response to drokeby

Has anyone come up with a fix for this? I'm dropping RED Epic 4K footage into a FCPX 1080 timeline, and then results I'm getting are terrible. The footage is extremely soft just like the example picture you have shown.

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Answer 2

Aug 3, 2017 5:32 AM in response to Level8studios

The same thing happened to me. I was dropping 4K footage from my RED Epic-W into a 1080 timeline and the image was so soft. I don't understand because everyone tells me that dropping a 4K clip into a 1080 timeline results in an extremely clear and crisp image. Hopefully apple comes up with a fix.

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Answer 3

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

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Answer 4

Russ H

Level 7

22,432 points

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

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Answer 5

drokeby Author

Level 1

7 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

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Answer 6

drokeby Author

Level 1

7 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

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Answer 7

drokeby Author

Level 1

7 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

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Answer 8

Aug 8, 2014 7:19 AM in response to drokeby

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

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Answer 9

Tom Wolsky

Level 10

152,815 points

Aug 8, 2014 7:31 AM in response to drokeby

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

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Answer 10

Aug 8, 2014 7:49 AM in response to Tom Wolsky

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

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.

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Answer 11

Russ H

Level 7

22,432 points

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

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Answer 12

drokeby Author

Level 1

7 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

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Answer 13

drokeby Author

Level 1

7 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

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Answer 14

drokeby Author

Level 1

7 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?

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Answer 15

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

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