Thread: HDR video of Experimental Music performance

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  1. #1 HDR video of Experimental Music performance 
    Little did I know that when I jumped on the opportunity to buy a Flanders Scientific XM-310K monitor at a newly lowered price in January that I would suddenly be granted MONTHS of time to really dive into the ins and outs of HDR video production.

    I hereby present this performance of me "playing" a Buchla Analog synthesizer:

    Some notes:

    1. No porgs were harmed in the production of this video

    2. The musical genre is ambient/experimental/random. But I think that after you train your ears a little, you'll hear the music in the randomness

    3. Shot on 3 RED cameras using Tokina Vista Primes (50mm and 105mm) and Tokina 11-20 Cinema ATX zoom.

    4. Analog audio recorded on SoundDevices 970 multi-track recorder

    5. Graded as REC 2100 / ST 2084 PQ (SDR version derived from DolbyVision trim pass with some hand-applied contrast adjustments)

    6. Graded with Davinci Resolve 16.2.2

    In the process I had a major revelation related to my HDR grading process that will make future HDR grades a lot less difficult:

    [reserving space in 2nd post]
    Michael Tiemann, Chapel Hill NC

    "Dream so big you can share!"
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  2. #2  
    My initial assumption was that grading an HDR project involved opening up a project in Resolve and then doing all the work from assembly to editing to grading to final export in that project. And perhaps it should be that way, but it really doesn't work that way today. All of the pieces that are needed are in Resolve today (well, all but the very last piece, which is to run mkvmerge to marry the H.265 MP4 file with a well-calibrated SDR LUT so that your gorgeous HDR footage doesn't look so horrible on conventional SDR displays that nobody would ever take a second look if first they saw it on a non-HDR screen). But even though the pieces are all there, they don't fit together well, due to the way Resolve factors various parameter settings.

    In Resolve, it is the PROJECT that defines all Timeline resolutions, Video monitoring resolutions, formats, and monitoring LUTs, output sizing, color spaces and gamma, etc. And though our goal may be to cut, grade, and ship UHD HDR masters, there are a number of steps along the way that must be done in different resolutions, different color spaces, or both. And while it may be temping to change the parameters that need to be changed in order to deal with these little excursions, therein lies the path to ruin, at least for me. I cannot say the number of times that I've caught myself out by making incomplete or inconsistent changes as I move from one phase of the HDR production process to another, and find I have wasted time and energy because those changes cause things to not work the way they should in other phases of the production process.

    But there is a nifty way to solve this problem, and it is to subdivide the different phases of the process into wholly separate projects that each have their own self-consistent PROJECT settings, and then to use Dynamic Project Switching and Power Grades to quickly and easily move from one phase to the next in a consistent fashion. To wit:

    Phase 1 is assemply and editing, and what most of us probably think of as THE PROJECT when we are creating our UHD HDR master. In Phase 1 we work with the resolution, color space, gamma, etc., that best serves our needs for editing and grading our material. We are not immediately concerned with the vagaries of solving the SDR problem but only the HDR deliverables.

    Phase 2 is where we turn on DolbyVision and let it analyze the HDR deliverable created in Phase 1 for the creation of an SDR LUT in Phase 3. There's a nifty feature if you are using a high-end Decklink card (I use the Decklink 8K), which is enabled via the "Use dual outputs for SDI" project setting. This allows one to do a side-by-side HDR and SDR grade by connecting the A output of a dual-output device to the HDR monitor and the B output to an SDR monitor (in my case, an FSI DM-240). But as also published in the manual, this is limited to using HD resolution, which is a PROJECT setting that needs to be changed. So we change it for the Phase 2 project. If we need to go back to Phase 1 (which happens ALL THE TIME), our project settings are re-set to correctly produce a new HDR master. Nice! When we think we have a good DolbyVision pass, we save that as a grade to a Power Grade folder.

    Phase 3 is where we actually generate the SDR LUT using the Resolve LUT Analysis pattern. This, too, requires changes to the PROJECT settings: we need to be in an SDR color space, and we need a timeline resolution of HD. We import the phase 1 HDR deliverable and apply the Power Grade from Phase 2 to see how things look in the SDR world on our SDR monitor. It might look great. It might look like a few tweaks will get it there. It might look like one is best off ignoring the DolbyVision pass and grading the SDR look by hand. And it might be that the best solution is to go back to Phase 1 and re-think what the HDR master should really look like. Whatever. When the (possibly null) LUT-compatible operations give us an acceptable SDR grade, we save that grade as a still, apply that still to the LUT Analysis image, then generate a LUT using Resolve's LUT Image analysis procedure.

    In Phase 4 we are back to UHD/HDR resolution and color space and all we need to do is to export our master as an H.265 MP4 asset with a Main 10 profile. Version 16.2.2 has made this a good 10x faster on my machine. Nice! What is not nice is that Resolve doesn't exactly honor the PROJECT settings on the Delivery page. That is, I can say that I want to deliver MP4 H.265, but when I create a fresh project and apply the Phase 4 preset, for some reason it defaults to a QuickTime container, not MP4. No problem: I can create a Delivery Preset that DOES do what I want. And because we are likely using all the same output color space and resolution as Phase 1, it could be that I just go back to Phase 1, create a timeline, import the master intermediate file, go to the Deliver page, click the UHD HDR preset for that page and it will add the correct delivery settings to the already-correct project settings. Or it can be its own itty bitty project.

    Phase 5 happens outside of Resolve. This is where we use mkvmerge to marry the H.265 MP4 file with the SDR LUT created in Phase 3. The resulting mkv file is now ready for YouTube.
    Michael Tiemann, Chapel Hill NC

    "Dream so big you can share!"
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  3. #3  
    The one other thing I discovered is that it really, really helps to use Remote Grades with RED footage. This was, I believe, a default for all media back in the Resolve 9 days, but the new default is that new clips use Local Grades. Here's why that's terrible:

    Let's assume for the moment that most RED clips begin and end in a consistent context (i.e., they don't go through a doorway from indoor lighting to outdoor lighting). We can do our best to get ISO, WB, and Tint correct on set. We can do our best to get those parameters looking good as we assemble our media. But inevitably, during editing and grading, one is bound to discover some clip where it just makes more sense to change some RAW parameters than to keep fighting against whatever those parameters were previously set to.

    If, during the editing process, we created many little clips from that troublesome master clip, if we use local grades, then every one of the resulting clips has its own RAW parameters that need to be changed. What a pain!

    It is also a pain that while Group Pre-Clip grades would be the perfect place to gather together a set of clips that should all follow the same RAW parameters (it is a PRE-CLIP after all!), that's not how Group Pre-clips work.

    But Remote Grades do work this way. When you change the RAW parameters on a Remote Grade, every clip connected to the original media file change in concert, which is exactly what we want! In the rare cases that we really do want to dissociate one clip from all the others, we can make THAT clip use a Local Grade and change RAW parameters without affecting other clips.

    You may wonder "what the heck does this have to do with Dynamic Project Switching and Power Grades?" and the answer is: it's another little thing I discovered as I discovered just how non-linear the HDR production process is. I find myself going backward and forward through decisions much farther and much more frequently than when I was only grading for SDR. And so I thought it helpful to share this other technique for making it easier to maintain consistency as one moves backward and forward through the production process.

    Thanks for reading!
    Michael Tiemann, Chapel Hill NC

    "Dream so big you can share!"
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  4. #4  
    Moderator Phil Holland's Avatar
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    Apr 2007
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    Firstly, now I know who has all the cables. All of them. Every single one :)

    But yes, there is a moderate amount of chaos and frustration still in the world of HDR and SDR grading even once crafting an SDR Trim Pass.

    The core variances between a wider color and gamut space and how those are reflected in essentially two different worlds can lead to some interesting questions along the way. Specifically with HDR being what it is and what you can possibly do with it I find myself asking questions often regarding the color itself. A project I did with Samsung a while back I mentioned with had to decided "what green is" in relationship to a very saturated and bright green.

    I suspect much of this will be easier soon. Or have slightly newer ways to tackle all this.
    Phil Holland - Cinematographer - Los Angeles
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