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more vfx from reddit, exr, linearization
by Andrew Randrianasulu 07 Nov '23

07 Nov '23

https://www.reddit.com/r/vfx/comments/ptk6ej/confusion_about_floating_point… well, I think this answer answers it ... Q first: ===== Confusion about Floating Point in Color Space Transforms/Management from Learning <https://www.reddit.com/r/vfx/?f=flair_name%3A%22Learning%22> Dear VFX Gurus/Professionals, I am not a VFX person at all. My question is more from a Color Management standpoint. And seeing how VFX artists follow the same rules as colorists(I'm not really a colorist either just someone who developed a bit of a hobby recently) in color management and equally have to deal with the confusing physics of light, I was wondering if you fine people could enlighten me. To explain my confusion I'm going to use an example of a hypothetical camera sensor which CLIPS White at a max 1000% scene linear reflectance and crushes blacks at 0% light (I know there is no such thing as 0% light but it just makes the numbers easier to deal with). I've attached below a Hypothetical 10bit Log Transform and a 16bit Linear RAW graph of the Input of Linear Light and Code value output(The so called OETF). The output values are both in Code Value (and Normalized from 0-1) {img omitted} Now, as far as I understood, when the 10bit Log encoded image goes through a Color Space Transform the first thing that happens to it is that it gets "Linearized" to a 32bit Floating Point(This is part of the IDT or Input Transform in Davinci Resolve or in the case of ACES VFX workflow, 16bit half float) before any other thing happens to it. Now, I'm not a software developer or video engineer or anything of that sort but having read about Floating Point(which is much more confusing than integer values) it's been said that Floating Point allows for OUTPUT values greater than 1 and less than 0. The problem I'm having is understanding how does this relate to Scene Linear Reflectance getting matched to the output in Linear Floating Point? For instance is 100% light reflectance giving an output of 1(the highest possible value in integers)? Does a 500% reflectance give an output of 5?What about 1000% reflectance, would that be an output of 10 and would the graph end there?? Or am I completely way off and 1000% reflectance would still be an output of 1, just that between 0 and 1 there'd be approximately 4 billion values worth of data(then what's the point of having values greater than 1 and less than 0?) The thing that's tricking me is that the entire dynamic range of the camera gets squeezed into a 0-1 output range in the integer encoded camera files, but I can't understand what's happening with it when it becomes a Linearized 32bit Floating Point. On the one hand everyone says these (ACES Linear Gamma or Davinci Wide Gamut) are HDR workflows but the problem is everyone just uses 0 and 1's for their light inputs and for their outputs when they're showing the graphs. For all I know an Input of 1 could just mean a Reflectance of 100%(just like in Linear RGB) or it could mean a 1,000,000% reflectance(Which is indeed MEGA-HDR). And what of the outputs potentially being greater than 1 and less than 0(What does that even mean?) I'll admit I haven't really tried to truly understand Float Point Operations, perhaps that's where I am failing. How is this 32bit Floating Point any different than the Linear RAW(Other than it being 32 bit Float rather than 16 bit?). Are they exactly the same with the only difference being there is an infinitely bigger amount of data values between Output 1 and 0(which linearly maps 0 - 1000% light reflectance)? What's the significance of having Output values greater than 1 and less than 0? Just very lost on this. And yes I have read multiple articles on this(Chris Brejons, ACES Manual, etc...) but the lightbulb isn't turning on for some reason. Feel free to correct me since as an amateur I definitely need guidance. Thanks ===== Welcome to the fun of colorspace. The whole thing is a pain. I've set up some facility level color pipelines (camera to broadcast), and even when you have a decent grasp of it, it's still basically a nightmare. A properly linearized image, rendered to EXR, will show values greater than 1, in my example earlier, they'd read 13-16 and everything in between. that's what half float (16) and float (32) allow to happen. But, and this is a big one, most container formats can't support values over 1. So historically LOG images have always been encoded with a LOG curve to jam their data into that 0-1 range. So it's important to note which colorspace transform has been applied to create the output image. Nuke makes it explicit to the format type, Resolve defaults to gamma 2.4 unless otherwise changed at the project level. The note above about reading in RAW, IIRC, is to make sure all the data is pulled in (no clipping) and then the correct colorspace transform is applied in app, pushing the super white values above 1. This was done for a couple reasons, a) to again keep all the data, and b) to allow any legal -> full range expansion before applying the colorspace move. It's less prevalent now, but there used to be a workflow where the camera SDI was outputting a legal feed, and the outboard capture decks were were also applying a full -> legal transform, creating master files that were double legalized. A lot of folks still render EXR with the LOG curve applied, so it's still technically 0-1 range. This is also the safest way for VFX vendors because if we reapply the same log curve on export, when it gets to the color house it will be apples to apples the same regardless of how they linearize (same as source). In theory the best practice would be to linearize the footage and leave it linear, but in reality that's problematic, as each software suite uses slightly different math to linearize. ACES color management is meant to solve this, but again most folks don't actually work in ACES correctly, to be fair most folks don't manage color is Resolve correctly either though. Also, I've seen this a few times, depending on where you start, I've noticed that some people speak in opposite jargon. IE when they say "log" they mean "was log, has been linearized" and when they say "linear" they mean flat raw log. When I refer to footage as log I mean very flat looking camera native, and when I say linearized I'm referring to footage that looks much closer to how we would see it if we were there on the day. ==== quote end ===== So .... it seems to be software-dependent what kind of values it can put in fp32 EXRs ....

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Plugins in integer or in float
by Andrea paz 07 Nov '23

07 Nov '23

>From the source code we can tell if a plugin works in 32 bit float or 8/10 bit integer? I don't know, maybe by searching for the string "float" in the code or something like that? Or the normalized range (0-1.0) instead of the range (0-255), etc. It would be important to put this information in the manual because, for example, I know that Histogram works with integers and this can lead to clipping (with loss of information) in highlights or deep blacks. In contrast, Blue Banana works in floats.

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Blue Banana, again
by Andrea paz 04 Nov '23

04 Nov '23

The revision of the manual on the plugin chapter is not yet finished, and for that I apologize to everyone, especially Phyllis for the extra workload. I have added tips to Blue Banana and made minor corrections. But I have left untouched the parts that I don't understand well and that don't seem clear to me. If anyone can suggest improvements I would be grateful. I also attach the txt that contains the additions, but they do not show where I put them in the manual. Also in these, if you find errors in them, please report it to me.

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No release this month
by Phyllis Smith 01 Nov '23

01 Nov '23

Since the only change is an update of libvpx from 1.13.0 to 1.13.1, there is no new release this month. This library update includes a fix for a vulnerability so users who do their own build may want to consider using the latest GIT for a new build..

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nvenc on latest appimage works!
by Andrew Randrianasulu 30 Oct '23

30 Oct '23

So, I compiled 64-bit proprietary nvidia driver on Salix 15.0 x64 xfce (by downloading and fully compiling kernel from kernel.org, then using NVIDIA-Linux-x86_64-470.199.02.run file from Nvidia website. anf compiled ffmpeg 4.4 against ff-nvidia-headers from salix repo. And fullhd video was going at 65 fps! Cingg was at just 30, but I guess this is expected due to all this redownloading via pci-e. blog where I found info: https://garysparks.info/post/can-a-geforce-gt710-nvenc/ so, I hopefully have customized nvidia binary installer to test on live dvd my gpu's nvenc/nvdec !

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ffmpeg 6.1 probably delayed ?
by Andrew Randrianasulu 29 Oct '23

29 Oct '23

http://ffmpeg.org/pipermail/ffmpeg-devel/2023-October/316264.html

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Blue Banana
by Andrea paz 29 Oct '23

29 Oct '23

I own a book on Color Correction that is outstanding in the quality and clarity of its explanations. The book is "Color Correction Handbook" by Alexis Van Hurkman, which I recommend to those interested in grading. There is a whole sample chapter on the publisher's website about HSL Qualifiers (our Blue Banana); try to read it because it is really extensive and useful to us CinGG users as well: https://www.peachpit.com/articles/article.aspx?p=1681373

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ffmpeg.git.patch10 started to fail ...
by Andrew Randrianasulu 28 Oct '23

28 Oct '23

Because ffmpeg 6.1 still not branched I guess we better to look into relevant changes ... and adapt our patch.

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Histogram plugin
by Andrea paz 23 Oct '23

23 Oct '23

I was rereading the manual about the Histogram plugin and there are things that I don't understand: 1- Is there no longer a frame interval averaging function (Frames button)? When was it taken out? Perhaps on this occasion? https://www.mail-archive.com/[email protected]/msg02691.html (moreover, the images are to be replaced) 2-I don't quite understand the concept of "Sum" instead of "max." The explanations are not clear to me. Can anyone clarify to me the behavior of the plugin with respect to Histogram Bezier, scopes and various color models? The explanation in the manual (section: Theory) is taken from here: https://www.mail-archive.com/[email protected]/msg01834.html

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Varied Standard Shortcuts AppImage version for testing
by Phyllis Smith 14 Oct '23

14 Oct '23

There is a modified Shortcuts AppImage version for testing on 64-bit O/S which is set up to be more in sync with what is considered to be "Standard" shortcuts for NLEs.. IgorB uses these and prepared a listing of the alternatives as shown below. If there are users who test these and prefer the more Standard ones, I can create an AppImage at the same time as what is released. It is currently at: https://cinelerra-gg.org/download/testing/modified_shortcuts.AppImage --------------------- Changed shortcuts to Standard Shortcuts - only English version for the caption/hints. The texts in the menu and the captions of the icons, written with the '-' character between the Special key and the key, for example "Shift-s", have been replaced by the '+' character. And the letters are always in capital letters although Shift is not pressed. Many, if not all the other NLE programs use this notation. Some shortcuts like "BD Render... (Ctrl+Shift+d)" and "DVD Render... (Alt+d) have been deleted because they are not used frequently. These shortcuts are very useful because the keys more frequently used have priority in editing: one hand (left) on the keyboard and the other hand (right) on the mouse. /* ********************************************************************** */ Goal: Changing some shortcuts to a NLE's standard shortcuts. For example: J - K - L (Play Normal reverse - Stop- Play Normal forward) if pressed twice J (or L), its Play Fast or Normal. I - O (InPoint - OutPoint) A - S (Jump backwards next cut - Jump forwards next cut) If an shortcut on After column has a '+' symbol (for example: + 'I'), it means that it is added to the old shortcut/s on Before column and also that that shortcut has been take from an old shortcut (of course), which it has another key. ----------------------------------+-------------------+-------------------+ Description | Shortcut | Before | After ----------------------------------+-------------------+-------------------+ -To clip | 'i' | Ctrl+I -Scroll window timeline... left | LeftArrow, ',' | LeftArrow -Scroll window timeline... right | RightArrow, '. | RightArrow -Label | 'l' | ''' (single quote) -Go to | 'g' | Ctrl+G -Generate keyframes... tweeking | 'j' | 'G' -Jump forward... next Keyframes | 'k' | Shift+Right Arrow -Jump backwards... next Keyframes | Shift+K | Shift+Left Arrow -New Project... | 'n' | Ctrl+N -Load files... | 'o' | Ctrl+O -Save | 's' | Ctrl+S -Save as... | Shift+S | Ctrl+Shift+S -Save Session | Ctrl+S | (null) -Select-> All | 'a' | Ctrl+A -Deselect All | 'a' or null | Ctrl+Shift+A -Select Edits | Ctrl+Alt+' | Ctrl+Alt+A -Undo | 'z', Ctrl+Z | Ctrl+Z -Redo | Shift+Z | Shift+Z -InPoint | '[', '<' | + 'I' -OutPoint | ']', '>' | + 'O' -Play Normal reverse | NumKP 6, Alt+O | + 'J' Normal&Fast -Play Stop | NumKP 0, Alt+M | + 'K' -Play Normal forward | NumKP 3, Alt+L | + 'L' Normal&Fast -Jump backwards to the next cut | Alt+LeftArrow | + 'A' -Jump forwards to the next cut | Alt+RightArrow | + 'S' -One Frame back | NumKP 4, Alt+U | + ',' (comma) -One Frame forward | NumKP 1, Alt+J | + '.' (period) | | -Load window: Select All files | Ctrl+A | Ctrl+A -Load window: Deselect All files | Ctrl+Z | Ctrl+Shift+A -BD Render... | Ctrl+Shift+d | (null) -DVD Render... | Alt+d | (null) -Delete last track | 'd'->Ctrl+D | Ctrl+D -Quit | 'q' | Ctrl+Q -Settings-> Save settings now | Ctrl+Shift+S | Shift+S -Settings-> Align cursor on frames| Ctrl+A | Ctrl+F ----------------------------------+-------------------+-------------------+ To summarize the jumps backwards and forward: ----------------------------------+-------------------+-------------------+ -Jump backwards to the next cut | Alt+LeftArrow, 'A' -Jump forwards to the next cut | Alt+RightArrow, 'S' -Jump backwards to the next label | Ctrl+LeftArrow -Jump selecting forward label | Ctrl+Shift+RightArrow -Jump selecting backwards label | Ctrl+Shift+LeftArrow -Jump forwards to the next label | Ctrl+RightArrow -Jump backwards... next Keyframes | Shift+LeftArrow -Jump forward... next Keyframes | Shift+RightArrow -Jump backwards to the next Autos | Ctrl+Shift+Alt+LeftArrow (only works on UbuntuStudio) -Jump forward to the next Autos | Ctrl+Shift+Alt+RightArrow (only works on UbuntuStudio) ----------------------------------+-------------------+-------------------+ /* ********************************************************************** */

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