Improving HDR -> SDR tone mapping

Hi Sam,

I’ve seen that you’re working on HDR → SDR tone mapping and I thought I’d make a suggestion here. It seems to me that you’re using a simple LUT approach, which is fine.

FYI, on AVSForum there are many JVC projector users who’ve worked with a python tool created by “arve” which creates custom LUT curves for HDR → SDR tone mapping. Users seem to be quite happy with the results they get this way. Maybe you could use the output of this tool to get improved HDR → SDR LUTs for the Vero 4K, too? Basically the “arve” tool creates a custom RGB gamma ramp which users then load into their JVC projectors. This makes it possible even for older generation JVC projectors to display HDR content “properly”, even though the older models don’t officially support HDR at all. The tool outputs a readable text file with the curve data in it. Here’s the link to the tool.

If you’re interested, I can ask one of the more knowledge AVSForum users about which exact curve parameters (for that “arve” tool) works best for them and list them here.

What do you think?

At this stage, you’d need to rebuild the kernel after every change.

It’s somerhing that we should look at later if we fully expose customisable LUTs via user space


Of course having customisable LUTs would be nice. But I was more thinking of improving the stock HDR -> SDR LUTs to improve the image quality the Vero 4K outputs by default. I could help provide the necessary LUTs for you for that purpose, if you’re interested.

I see this is an old thread but I was wondering if there has been any progress on this front. I have a JVC RS540 and wondering if I can load a customer gamma curve into Vero 4k+.

It would help to know what software you are running.

Are you using the 4.9 video stack?
This has improvements that may remove your need to load a custom curve.

We do have plans to support custom curves in the near future.

CC @grahamh

This functionality is not available out of the box but can be added. What would be the format of the custom curves? I understand JVC supports custom curves - what is your experience of that?

Still on original the unit came with, 3.14 I believe. Since everything was working I didn’t look into upgrading the 4.9 . I will give it a shot.

I just bought the JVC this weekend. So I am still new to this. But from what I have been reading, the custom curves available from forum members @ AVS Forum indicates the JVC curves are in jgd and conf file format.

Can I suggest you get to know your PJ first and maybe have a play with the custom curves others have produced. If you can’t get good results from those, come back to us. We are working on adding some way for users to apply their own LUTs but it might be a while yet before we have something that’s user-friendly.

Thanks grahamh. I have found some curves other have produced and will test out those.

I upgraded to 4.9 and noticed much improvement in standard HD playback. Everything just feels right without me messing around with my projector settings (both the JVC RS540 and Epson 5040UB). To compare, I played the same material with Apple TV 4K and Nvidia Shield Pro, and I had to adjust the gamma on both projectors to get it right and even then I preferred the Vero 4k+. Is this a placebo effect? lol

In any case, very happy with my Vero 4k+. Will try HDR playback over the weekend and see if that has improved too. Thanks Sam!!

Interesting. There’s no difference between 3.14 and 4.9 for HD unless perhaps you’d been fiddling with the limited/full range or YCC/RGB settings.

Yeah, could be the limited/full range setting. I did not fiddle with any of the settings on the Vero 4k+. I will check the setting on the other players as I tweaked those before. I use Kodi, SPMC, MrMC and Infuse on the other media streamers.