- Cin - Cinelerra-GG Mailing Lists

Tonemapper algorithms (EXR input, require OpenGL)
by Andrew Randrianasulu 22 Apr '25

22 Apr '25

https://github.com/tizian/tonemapper found while looking at why F_tonemap visibly misbehaves for me ...

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Even more on HDR in video
by Andrew Randrianasulu 22 Apr '25

22 Apr '25

https://lightillusion.com/what_is_hdr.html This page points out something interesting: you can have only *some* components of "HDR" in any particular display, so for example display can be Wide Gamut bt2020 BUT SDR! And/or smaller than 4k ;) === Additionally, the individual aspects of the HDR specifications can, and often are, used in isolation. For example, there is nothing to stop a standard gamut display (Rec709), with standard HD or even SD resolution, working with an HDR EOTF with high contrast range. ====== It also points out that viewing environment even more important for both HDR schemas - PQ and HLG. Interestingly it includes table where specific (integer!) signal levels correspond to specific luminance in nits. I still can't fully wrap my mind around what exactly "nit" represent, but apparently in HDR you really grade relative to specific max/min luminance of your mastering display AND suitable HDR display/TV must do some tone mapping magic if your defined luminance (?) goes above level that monitor/tv can show. There was equation on page about tonemapping https://64.github.io/tonemapping/ === Converting a linear RGB triple to a luminance value is easy: L=0.2126R+0.7152G+0.0722B ==== but I am not sure if it works for *any* useful RGB values? Also, issue with viewing distance wil play differently for those VR setups?

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HDR -> sdr tonemap on cpu only
by Andrew Randrianasulu 22 Apr '25

22 Apr '25

Many (if not all) ffmpeg guides insist on using either libplacebo (vulkan API on GPU) or zscale (not available in some ffmpeg builds). Here I found collection of .cube files for doing REC2020 TO rec709. https://www.reddit.com/r/premiere/comments/12t9mh8/convert_hdr_to_sdr/ https://drive.google.com/file/d/1HQGKE5Fzg_W5vsP8wJcmzRIAtCRKevsV/view I extracted one .cube file and run this ffmpeg command (at 1.4 fps on Termux) ffmpeg -i storage/downloads/iPhone11_4K-recorder_59.940HDR10.mov -vf lut3d=file=REC2020PQto709v1.cube:interp=tetrahedral,scale=1280:-2 ~/1.mp4 and it sort of worked, while I think mpv/libplacebo did better job on my desktop. But even just in mpv I had tons of dropped frames, and decoding in cingg without any tonemapping was at may be 9 fps max, out of 60. Ow :( For some reason just throwing F_tonemap to timeline resulted in extremely dark image no matter the settings. I pushed it up by brightness/contrast native plugin but I do not think you supposed to do that? sw tonemapper was added to ffmpeg in 2017 https://github.com/FFmpeg/FFmpeg/blob/master/libavfilter/vf_tonemap.c

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EOTF, PQ, HLG ....
by Andrew Randrianasulu 22 Apr '25

22 Apr '25

It seems that at least for "PQ" HDR systems their EOTF can be used to give some reading into waveform scopes etc? As they set to "Nits" and not -10-110% as usual for SDR (and may be Hybrid Log Gamma?) systems. https://github.com/colour-science/colour/discussions/712 ===== A true PQ curve is an absolute cv-nit scale. The normalized CVs of a few different nit levels are: 100 nit = 0.5081 600 nit = 0.6963 1000 nit = 0.7518 4000 = 0.9026 Here's Steve Shaw's write-up on the matter which further backs up my concerns: https://www.lightillusion.com/uhdtv.html [image: hdr_luminance_levels] <https://user-images.githubusercontent.com/30381480/38954716-4812c0ba-4307-1…> This behavior is how reference displays should work (notwithstanding HDR metadata and consumer-grade secret-sauce), and I can confirm is the way the Dolby Pulsar, Sony x300, and x550 all work. When fed RGB(.5081, .5081, .5081) on all three displays set to D65 ST2084, you should measure 100 nits. If you feed a linear ramp to all the displays, you will see a hard clip of all values above the associated code value for that display's peak luminance. ===== quote end ==== Apple's document HDR and Wide Color Gamut in Final Cut Pro White Paper November 2020 says: ==== Wide Color Gamut Displays that support wider color gamuts with a traditional luminance range are sometimes referred to as wide-gamut, standard-dynamicrange (SDR) displays. Current models of Mac, iPhone, and iPad support a wider-gamut SDR color space called Display P3. Display P3 uses the same color gamut as DCI P3, the standard for movie theater digital projectors, combined with a white point and gamma appropriate for typical viewing environments. The figure below shows that the P3 color gamut contains more colors than the Rec. 709 gamut, with notable improvements in the range of red and green areas of the color spectrum. [..] High Dynamic Range Displays that support both wider color gamuts and higher luminance ranges are referred to as high-dynamic-range (HDR) displays. HDR displays can produce not only high peak luminance values but also very low black levels, revealing more detail in both shadows and highlights. HDR displays typically reach peak brightness levels above 1000 nits while maintaining very high contrast ratios, much higher than the brightness levels and contrast ratios of SDR displays. These levels of brightness mean that images appear more true to life, with a dynamic range that more closely reflects what the eye sees in the real world. The figure below shows how increased brightness levels (measured in nits) combined with a wider color gamut greatly expand the range of reproducible color. HDR displays typically process video at 10 bits per color component rather than 8 bits. The additional color data lets HDR displays render more discrete steps from the minimum to maximum brightness value in each color. In order to encode and transmit HDR images more efficiently, new mathematical transfer functions are used instead of gamma. Two popular standards are the Perceptual Quantizer (PQ) function, defined in both SMPTE ST 2084 and ITU-R Recommendation BT.2100, and Hybrid Log-Gamma (HLG), also defined in Rec. 2100. About Changing a Project’s Color Space After you set a library to wide-gamut HDR, any project with HD resolution or higher created in that library can be set to one of the following color spaces using the Modify command in the Project Properties inspector (described in step 3 above): • Standard - Rec. 709 • Wide Gamut - Rec. 2020 • Wide Gamut HDR - Rec. 2020 PQ • Wide Gamut HDR - Rec. 2020 HLG [..] When performing these adjustments, it may be helpful to show the Waveform video scope and set it to either RGB Parade or RGB Overlay view. In these views, the vertical axis of the waveform is labeled in units of cd/m2 (nits), which is a measure of the display’s output brightness level corresponding to the PQ signal level. Note that for the Luma and Chroma views, and for any non-PQ content, the vertical axis reverts to IRE (where 100 IRE represents 100% signal level). This is because the waveform signal in these cases does not correspond directly to absolute cd/m2 values. === quote ends here finally ===== So, it seems that we currently lack easy user choice between PQ/HLG variants of Wide Gamut bt 2020 color space, I think in ffmpeg/swscale they hide as "trc" (transfer curve) ... but I can be wrong. Also tonemapper on cpu, at least on my potato, tend to be slow, unless you downscale to like 1/4 out of 4k source? So it will be helpful to look into vf_libplacebo, opencl_tonemap etc on machines where they work. Sorry if it feels like too much of confusing info, I think while technically cingg currently capable of *encoding* at least some variants of HDR - more accurate displaying, easy user settings, waveform scope display "morphing" to HDR mode, HDR10+ dynamic metadata calculations all missed, relative to FCP/Resolve.

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Optics! Offtop but may be interesting
by Andrew Randrianasulu 22 Apr '25

22 Apr '25

https://opg.optica.org/oe/fulltext.cfm?uri=oe-30-2-1036&id=466401 "Optics Express Vol. 30, Issue 2, pp. 1036-1055 (2022) • https://doi.org/10.1364/OE.447375 General solution to the calculation of peak luminance of primaries in multi-primary display systems Binghui Yao, Liquan Zhu, Yuhua Yang, Guan Wang, Chun Gu, and Lixin Xu" According to this modern displays (tm) can use more than 3 primary colors ... We must be happy that all this encapsulated by some black box monitor firmware ;)

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HDR *camera* monitor
by Andrew Randrianasulu 20 Apr '25

20 Apr '25

just 10 inch, but it said to support HDR (via presets and user LUTs) so I wonder if it can be used for technical development of hdmi hdr output? https://www.feelworld.cn/ShowInfo.aspx?id=743&py=FEELWORLD-LUT11S-10-1-Inch… wow, this is URL ..... pros: cheap, compared to real HDR professional big monitors. cons: physically small.

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libtiff 4.7.0 and libtheora 1.2.0?
by Andrew Randrianasulu 17 Apr '25

17 Apr '25

noted that termux moved to it ... https://libtiff.gitlab.io/libtiff/ I have local patch for building 4.7.0 instead of 4.6.0t but I rarely use tiff output ..... Another possible library update is libtheora 1.2.0 https://www.theora.org/downloads/ http://downloads.xiph.org/releases/theora/libtheora-1.2.0.tar.gz https://www.phoronix.com/news/Theora-1.2-Released

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Final Cut Pro goes to 120-125% in its scope tools
by Andrew Randrianasulu 17 Apr '25

17 Apr '25

https://i.ibb.co/whgznbHg/Screen-Shot-2025-04-17-at-17-37-47.png So *I think* internally it allows some under/overshots, and their visual monitoring. see for example also this vid (seems that back in 2011 shape for secondary CC was limited TO round corner rectangle/ellipse) https://m.youtube.com/watch?v=Fx-frNPALk0 Here it differs from DaVinci Resolve scopes ....

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Adobe Premiere (2021) and HDR
by Andrew Randrianasulu 17 Apr '25

17 Apr '25

was looking at how exactly HDR info travels in production environment. https://community.adobe.com/t5/premiere-pro-beta-discussions/discuss-color-… ===== Francis-Crossman Adobe Employee Sep 17, 2021 This expands the list of color managed codecs. H264/HEVC represents the majority of DSLR and mirrorless prosumer cameras on the market, and XAVC-L / XAVC Slog are heavily used in broadcast HDR workflows. “Color managed” means that Premiere Pro read the color tags in the file metadata and accurately converts the file to the sequence color space. If the color spaces of the file and sequence are the same, the Premiere Pro passes the colors through to the sequence without conversion. Color management is necessary for HDR production. Codecs that are not color managed will always be interpreted as Rec709, which worked just fine for a long time. But with HDR becoming more and more mainstream, proper color management is necessary. Full list of color managed codecs Codec Wrapper Color Space New? Apple ProRes · 422 HQ · 4444 · 4444 XQ .MOV Rec. 709 Rec. 2100 HLG Rec. 2100 PQ Previously supported Sony XAVC-I (all intra) .MXF Rec. 709 Rec. 2100 HLG Previously supported Sony XAVC-L (long GOP) .MXF Rec. 709 Rec. 2100 HLG NEW H.264 / HEVC (H.264) .MP4, .MOV Rec. 709 Rec. 2100 HLG Rec. 2100 PQ NEW ===== so in this case he talked about importing colorspace-tagged material, not embedded icc or display side. x264 support for XVAC-intra + HDR metadata was merged few years ago: https://forum.doom9.org/showthread.php?p=1950549 https://forum.doom9.org/showthread.php?p=1940382 https://code.videolan.org/videolan/x264/-/merge_requests/5 I still wonder how you get those values for mastering display? G(x,y)B(x,y)R(x,y)WP(x,y)L(max,min) hm may be like here, vua libdisplayinfo/EDID https://github.com/doitsujin/dxvk/blob/master/src/wsi/wsi_edid.cpp#L14 from https://github.com/libsdl-org/SDL/issues/6587 but ofc there us dev blog saying edid can be incomplete/inaccurate: https://planet.kde.org/xavers-blog-2024-05-10-hdr-and-color-management-in-k… ==== There is a fourth option though: Use the color information from the display’s EDID. In Plasma 6.1, you can simply select this in the display settings. color profile settings Note that it comes with some caveats too: the EDID only describes colors with the default display settings, so if you change the “picture mode” or similar things in the display settings, the values may not be correct anymore the manufacturer may not measure every panel and just put generic values for the display model into the EDID the manufacturer may put completely wrong values in there (which is why this is disabled by default) even when correct values are provided, ICC profiles have much more detailed information on the display’s behavior than the EDID can contain ==== but at least this round of search shows that SDL(2.x, 3?) does have some support for HDR now, so may be it also an option!

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Avid secondary color correction.
by Andrew Randrianasulu 17 Apr '25

17 Apr '25

https://m.youtube.com/watch?v=ANYSVEh2QOE "Avid Online Learning — Media Composer: Secondary Color Grading" around 30 min. You can see more specialized tools, but also basic shapes used.

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