How to do 3D Lut color correction (.3DL .Cube) with avisynth(+) ?

[StvG]

Thanks.

[ErazorTT]

I'm having a lut which when using ffmpeg produces the expected behaviour, but when using the cube function returns unexpected things.
The following image shows the result, on the right part there are these waves which are unexpected, and are also not there using ffmpeg.


However when using ffmpeg I'm getting this:


Here are all files I am using:
hlg_test.7z

The command for ffmpeg is:
ffmpeg -i GreyRamp16bits.png -vf lut3d=lut_4000_3.0.cube -pix_fmt rgb48be GreyRamp16bits_converted.png

What is going on here, why the different results?

[Reel.Deel]

@ErazorTT

Does DGCube have the same problem? https://www.rationalqm.us/board/view...p=16092#p16092

[poisondeathray]

For reference, avs version , vpy version that it's based on , and Adobe get similar results

The difference is the default interpolation type for ffmpeg (tetrahedral) . Trilinear , pyramid, prism all produce the pattern to an extent

eg.
ffmpeg -i GreyRamp16bits.png -vf lut3d=lut_4000_3.0.cube:interp=trilinear -pix_fmt rgb48be GreyRamp16bits_converted_trilinear.png

[tormento]

Originally Posted by Reel.Deel

Does DGCube have the same problem?

Is it working for you? What card? Drivers?

[Reel.Deel]

Originally Posted by tormento

Is it working for you? What card? Drivers?

No, I am also getting access violation. I have not updated my drivers in a while so I was going to do that and see if it fixes the issue.

[ErazorTT]

Originally Posted by poisondeathray

For reference, avs version , vpy version that it's based on , and Adobe get similar results

The difference is the default interpolation type for ffmpeg (tetrahedral) . Trilinear , pyramid, prism all produce the pattern to an extent

eg.
ffmpeg -i GreyRamp16bits.png -vf lut3d=lut_4000_3.0.cube:interp=trilinear -pix_fmt rgb48be GreyRamp16bits_converted_trilinear.png

Oh that is a nice finding! So its the interpolation. Could this better interpolation be implemented into vscube (or DGCube for that matter)?

[ErazorTT]

Originally Posted by Reel.Deel

@ErazorTT

Does DGCube have the same problem? https://www.rationalqm.us/board/view...p=16092#p16092

I just found that DGCube needs 65x65x65 sized LUTs, so I tried again with one of that size. And yes, DGCube behaves that same as vscube.

[poisondeathray]

Originally Posted by ErazorTT

Could this better interpolation be implemented into vscube (or DGCube for that matter)?

It's debatable if a certain interpolation is going to be "better" for all situations;

But having more options is always welcome

You can try submitting a feature request
https://github.com/sekrit-twc/timecube/issues

[tormento]

Originally Posted by Reel.Deel

No, I am also getting access violation.

Generic size version has just been released.

[tormento]

Here is a new version supporting tetrahedral interpolation. It addresses ErazorTT's issue, as the artifacts do not occur with tetrahedral. Please read the new DGCube.txt file for details and be aware that the filter is now invoked as DGCube(). I'll add this to the timecube-derived Cube() filter as well. Also need to add Vapoursynth support to DGCube().

https://rationalqm.us/misc/DGCube.zip