Extreme glitches in 3D lut

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  • #6473

    Florian Höch
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    I am creating the madvr-format, as that is the only one that kodi understands. Comes from here: http://forum.kodi.tv/showthread.php?tid=202691

    I don’t see anything there that indicates Kodi supports the madVR 3D LUT format on Linux. It does seem to support ICC device link, which is the source for all the other formats anyway. You probably want a full range 3D LUT with Kodi if the limited range 3D LUT clips.

    #6479

    ((( atom )))
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    From post #52 on madvr-format is supported, so I guessed it should work.

    #6483

    Florian Höch
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    From post #52 on madvr-format is supported, so I guessed it should work.

    Ok, I didn’t go that far into the thread, only looked at the first and last page. For a madVR 3D LUT, the correct levels are always 16..235 (note that this is independent from any settings related to full range/limited in Kodi, the graphics driver and the TV! The correct setup in those is the one where levels above black are neither clipped nor black is raised. You can check this with one of the many test videos available from different sources, e.g. AVS HD 709. Levels above 16 should be visible in a dark room, and levels 16 and below should be black).

    #6484

    ((( atom )))
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    So I measure with grafics and TV at full RGB and create the icc and the 3dlut.

    Thats just what I did.
    I then found correct settings to display the AVR 709 test pattern. Using the icc profile only, loaded into my X-server black is visible precisely from level 17 upwards and white goes up to 234.

    Trying the same with the created 3dlut leads to a way darker picture, which tends to be reddish and causes banding.

    #6489

    Florian Höch
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    Trying the same with the created 3dlut leads to a way darker picture, which tends to be reddish and causes banding.

    Banding is usually caused by limited bit depth processing and/or no dithering on output. I would advise to test the equivalent device link that accompanies the 3D LUT outside Kodi, i.e. transform an image through the devicelink profile (cctiff -p devicelink.icc input.tif converted.tif) and view it in a non-colormanaged viewer(!) with linear video card gamma tables. Note the image should use video levels as that is what the 3D LUT/devicelink expects. I attached a video levels granger rainbow.

    Attachments:
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    #6492

    ((( atom )))
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    So I just checked with the latest measurement from last night which has enabled the “white level drift” compensation. Looks exactly the same. Too dark and reddish, banding present.

    Kodi from version 17 on is able (and enabled) to dither the output and using the icc-profile, I don’t ever notice any banding anymore, even in scenes that used to have it. So that seems to work quite well.

    Thx for the Granger rainbow. To make use of it, I have to find a way to turn it into a video, since to my understanding the 3dluts in kodi are only active when playing video. Actually there is no information about it, but if it was applied system-wide, I should notice a change in the UI when I apply it, and I don’t.

    How to test the device-link outside kodi sadly is beyond my scope, so I cannot do that.

    Again I do not understand, how can the icc-profile lead to a very satisfying picture and the 3dlut, created from that profile, can be so different in term of brightness and color.

    It is very hard to take pictures of dark scenes, otherwise I would attach some. In dark scenes the darker parts totally drown in red pixels, that seem rather large. hard to explain (as well)..

    I’d really love to work this one out, since I know (and saw in bits) that my hardware is very capable of performace far beyond “good”. I really want to make this stick throughout.

    #6495

    Florian Höch
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    How to test the device-link outside kodi sadly is beyond my scope, so I cannot do that.

    This would allow you to determine if the problem is within Kodi, which would be useful information…

    #6497

    ((( atom )))
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    OK, so I will look into that..

    #6545

    ((( atom )))
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    Ok, took me a while. because at first I didn’t know what the “device link” should be, but you actually gave me instructions, so I converted the image using the icc-profiles that came with the LUTs. Still unsure if I should do the profiling with the projector set to FULL or LIMITED, I tried both and made tifs for each of the results. I can spot something being wrong in the dark areas, but I don’t know what exactly that tells me. I guess you will be able to interpret them.

    Here they are:

    http://komeda-berlin.de/converted_ltd.tif

    http://komeda-berlin.de/converted_full.tif

    #6549

    Florian Höch
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    The granger rainbow image I attached is limited range, so needs to be used with a limited range device link or 3D LUT. Please attach the profiles as well (use the “Create compressed archive…” button in DisplayCAL next to settings, with the profile selected).

    #6551

    ((( atom )))
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    Here it is: http://komeda-berlin.de/RS40-RGB-FULL-ILAFPJ–X10J1.%231.2017-03-27.20-03%20.S.XYZLUT.zip

    The “FULL” in the name is wrong, forgot to change it before doing the “limited” measurement.

    #6570

    Florian Höch
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    Here it is: http://komeda-berlin.de/RS40-RGB-FULL-ILAFPJ–X10J1.%231.2017-03-27.20-03%20.S.XYZLUT.zip

    You’re driving the projector in full range, but it is expecting video range (as is evident from the measurement data where any levels below 16 are measured as zero). As a result, there’s bad clipping even before any profile or 3D LUT is in use, and the profile is unusable due to the clipping. So, the first step is to setup the video chain correctly, i.e. the PC needs to output limited range. This can usually be set in the video driver options.

    Then, you should enable white level drift compensation and re-calibrate/re-profile.

    #6577

    ((( atom )))
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    Ok, I will try that, thx for looking into this. I’ll report back.

    I am very confused about this, though, since I investigated this issue, before I set up the measurement and the recoomodation from the kodi.wiki is to set up the player limited, the gpu full and the projector limited again in order to achieve best results. -> From the summary under 2.2 of http://kodi.wiki/view/Video_levels_and_color_space

    To my understanding I send the limited content through the gpu (which just passes through the values as they are, 16 as 16, no conversion) and the projector “knows” to display 16 as the darkest possible value, giving me black.

    So is this plain wrong?

    #6580

    Florian Höch
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    I am very confused about this, though, since I investigated this issue, before I set up the measurement and the recoomodation from the kodi.wiki is to set up the player limited, the gpu full and the projector limited again in order to achieve best results. -> From the summary under 2.2 of http://kodi.wiki/view/Video_levels_and_color_space

    This can work, but it needs any application that wants to achieve correct output levels to do the conversion itself, and is just a bit of an awkward way to set things up generally, because the output will then only look correct in those applications, everything else will look incorrect (e.g. the desktop and UI elements). If you want to use this setup with DisplayCAL, you have to specify additional command line arguments to dispcal/dispread, namely the -E argument, which will make the Argyll tools produce limited range output (enable advanced options in the “Options” menu, then under advanced, choose “Set additional commandline arguments…” and enter -E into the text fields for both dispcal and dispread).

    #6582

    ((( atom )))
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    Aaah, thx for the explanation. Since I built a machine to run kodi and nothing else, this should be the way to go for me.

    I will give this a try once it’s dark and will check the results tomorrow night..

    I’ll be back!

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