Support forum for DG Tools

@dmcs

I appreciate the humor of the post you made, but in the current PC climate it could get us in trouble, so forgive me for deleting it.

gonca wrote: ↑

Tue May 15, 2018 4:04 pm

Sounds like you have ideas for the Fast Fourier Transform

This is CUDA land. Slow does not exist here.

I've got the cuFFT working. Here are pictures for flat and detailed windows:

While it is certainly usable to distinguish flat areas, the FFT magnitude plot differs from the one I get with a brute force fourier transform (C code, not FFT). The CUDA one seems compressed along the X axis. I want to look at that before trying to use this for the mitigation of equalization.

I found and fixed the pitch bug I had that was making skinny FFT plots. Now I will develop the metric based on the doughnut idea. After that will integrate it into the equalization code to make the strength of the equalization a function of the amount of detail in the area. Looking good so far.

Man, you are fast and good at coding
Well done

Thanks, gonca. It's not so much about the coding as it is the debugging. I have always been a kick-ass debugger, all modesty aside. It's easy to crank out code; making it actually work right is the challenge. But I am a good coder too.

I completed the metric (but my doughnut is a square one, hehe). Here it is in action. First the flat window (the first image is the input image and the second is the fourier transform image):


The detail metric for the flat window is 0.055790. And now the detailed window:


The detail metric for the detailed window is 0.903815. This gives a ratio of about 16:1 for the two metrics.

The metric is normalized for overall brightness of the window. It's clear that this metric effectively distinguishes flat areas from detailed areas.

Next step: integrate this metric into DGHDRtoSDR and use it to modulate the equalization.

I implemented batched FFT for all the windows in the frame with one execute call. This improved performance as expected. But more importantly, I experimented with the FFTW library and discovered that for my transform size (128 x 135 real-to-complex), multithreaded FFTW is about twice as fast as cuFFT! The reason of course is (yet again) the overhead of transferring data to/from the GPU. Using FFTW will also allow me to overlap the GPU activities and the CPU activities (kernel execution is asynchronous), whereas if I used cuFFT, everything would be running serially on the GPU.

So finally now I am ready to start integrating this metric into DGHDRtoSDR and to see if the banding due to equalization can be avoided. I'm really learning a lot!

It is, after all, the Fastest Fourier Transform in the West
Good to know you are still learning, good to keep the brain cells active and alive

Unfortunately, the FFT-based idea to salvage equalization is not working out, for two main reasons. First, the metric does not reliably distinguish flat areas in real video full frames. There is simply two much variance for it to make a clean cut. Second, equalization itself changes the overall brightness of the window, which produces a horrid effect in the full frame when not all windows are equalized. So for now I am removing this functionality. I doubt that it can be salvaged.

Here is DGHDRtoSDR 1.1:

* Equalization mechanism removed.

* Reinhard replaced with gamma. I find it works better.

* You can now crop and resize before calling DGHDRtoSDR().

* See the user manual for details and examples.

http://rationalqm.us/misc/DGHDRtoSDR_1.1.rar

Thanks for the update

I've tried the new gamma tonemap and noticed that the midtones are lacking in brightness.
However default is much better than Hable for the highlights.
Some comparisons and respective settings:

SDR

dghdrtosdr(impl="255",light=47,gamma=0.38)

DGHable(exposure=1.0, w=2.5)

Odd values for Hable but they're what I find work well when the highlights are not bright enough at default.
Reinhard (other than bad highlights) behaved similarly as Gamma does, but Hable has that extra 'w' parameter that makes the difference.

Try gamma of 0.40 to 0.42 and report back. Thank you.

gamma= 0.42 is the theoretically correct value. I set a lower one to bring out some black detail but probably set too low.

admin wrote: ↑

Mon May 21, 2018 4:53 pm

Try gamma of 0.40 to 0.42 and report back. Thank you.

gamma= 4.2 is the theoretically correct value. I set a lower one to bring out some black detail but probably set too low.

Typo, I guess?

For sure. Corrected, thank you.

Here's the same frame, gamma at 0.40 and 0.42
It does improve the contrast, though still dim in terms of brightness where light shines.
However the Hable method often results in some scenes brighter than SDR, so it might work better in places.

If I increase light, it only makes the paper overblown and loses detail there (which is already happening at 0.47)

dghdrtosdr(impl="255",light=47,gamma=0.40)
dghdrtosdr(impl="255",light=47,gamma=0.42)

Honestly, I cannot see the things you claim to see and they seem highly subjective to me in any case. So I'll just add Hable as an option and declare mission accomplished.

Yes sorry it is subjective, otherwise the tonemap is great

I added Hable:

http://rationalqm.us/misc/DGHDRtoSDR_1.2.rar

Please read the instructions carefully as parameters have changed.
If you'd like to argue for any different Hable default values just speak up.

I've got this weird green thing when using Hable in the latest DGHDRtoSDR_1.2.
Gamma mode:
My code for Hable mode:

Set up some samples for version 1.1, but I was a little late, updates are fast.
So here are some images for 1.2
Script is Images are resized to 1280x720 at 8 bits
HDRtoSDR 1-1 SDR 1-1 HDRtoSDR 1-2 SDR 1-2 HDRtoSDR 1-3 SDR 1-3 More samples can be quickly obtained if needed/desired

dmcs wrote: ↑

Tue May 22, 2018 3:54 pm

I've got this weird green thing when using Hable in the latest DGHDRtoSDR_1.2.

That's weird. Can I get your unprocessed source sample that produces this? I can't make it happen with my samples. Thank you.

EDIT: OK, I have a sample that shows it. It would still be great to get yours. It doesn't fail with impl="sw" for me, BTW. Investigating...

Thanks for the testing, gonca!

For comparison
Speed of script is over 128 FPS

admin wrote: ↑

Tue May 22, 2018 4:09 pm

Thanks for the testing, gonca!

The results with gamma look very good to me, might need a dash higher brightness.
But to be honest, no one approach with one set of default settings will be perfect for every source.
Right now we have gamma, Hable, and if the "old" plugin works, Reinhart
It takes very little time to create a script, and index a movie in order to load it into VDub
Then we can adjust settings, or approach, quickly until we get our desired results.
After all, a lot of this is subjective
Set it up to get the results you like

dmcs wrote: ↑

Tue May 22, 2018 3:54 pm

I've got this weird green thing when using Hable in the latest DGHDRtoSDR_1.2.

Please re-download and test again. Should be fixed.

Thanks for pointing this out.

admin wrote: ↑

Tue May 22, 2018 4:30 pm

Please re-download and test again. Should be fixed.

Thanks for pointing this out.

Yay!!! So, may I ask what was that?