Monster Guide: HDR10 in Resolve Studio 18 (Part IV)

Part I: Project settings

Part II: BT.2020 or P3-D65 Limited?

Part III: HDR Palette, project render settings, generate MaxCLL and MaxFall HDR10 metadata

Part IV: HDR to SDR Conversion LUT for YouTube

Part V: RAW

Part VI: The Grade

Part VII: The State of HDR Film Emulation LUTs & Plugins

Part VIII: Why HDR Production Monitors Matter

YouTube’s own HDR to SDR conversion is seldom satisfactory, which is why, for best results, we strongly recommend creating your own Look-Up Table for greater control. From YouTube’s Help page:

YouTube’s automated SDR downconversion is a convenient choice that can deliver good results with no effort. However, on challenging clips, it might not deliver the perfect result. We’re working on improving automated SDR downconversion so that it works great for all material.It’s possible to give a hint to YouTube’s SDR downconversion in the form of a 3D Look-Up Table, or LUT. To produce this LUT:

  1. Load your HDR video into a color grading app without applying any color management.
  2. Set your mastering display to Rec. 709 color and Gamma 2.4 transfer function.
  3. Apply an existing LUT that converts from Rec. 2020 + ST. 2084 to Rec. 709, and then in subsequent nodes, change primary correctors, curves, and keys to get the look you want.
  4. Export the LUT in the .cube format to the same folder as the HDR video.
  5. Select both the LUT and the HDR video, and drag and drop them on the metadata tool.

The tool will apply metadata for the BVM-X300, and also pack in the LUT to give hints to the SDR downconversion. 

Here’s our guide to bypassing YouTube’s own conversion:

1. Go to the GitHub page to download the HDR metadata tool. Click the Code button and download the metadata tool as a zip file.

2. Extract the zip file and place the extracted folder inside your Mac’s user folder.

3. Go to Google Drive and download the two free HDR to SDR conversion LUTs and the rtf text document.

4. Grab one of the LUTs and place it inside your Mac user folder.

5.  Place the rtf text document inside the user folder as well.

6. Copy your HDR movie over to the same folder.

7. Rename the HDR movie to or HDR_To_SDR_LUT.mp4. The file can be renamed back to its original name once we’re finished.

8. Open Terminal then navigate to the HDR metadata master folder you just placed inside your user folder then go to macOS and double click.

9. Right click on mkvmerge and select Show Package Contents.

10. Open Contents.

11. Open macOS.

12. Drag the mkvmerge file onto the Terminal window. This initiates YouTube’s HDR metadata tool. 

13. Open the rtf file and copy and paste the text into Terminal. Because the video was rendered in ProRes, we’re going to change it from mp4 to mov prior to copying and pasting into Terminal.

A pop-up may appear saying the app cannot be opened because the developer cannot be identified.

In which case, go to System Preferences > Security & Privacy and click on Open Anyway.

14. Once completed, you’ll see a brand new mkv file inside your user folder. This is a duplicate of your HDR video rewrapped inside of an mkv container only now it’s got the custom LUT embedded inside the file.

15. When you upload the file to YouTube, it will use our custom LUT rather that its default one.

Once the video has finished processing, the SDR version will have our LUT applied and the HDR version will remain the same.

To Make Your Own Color Space Conversion LUT:

1. Open Resolve and create a new project.

2. Leave all color management settings at their default configurations.

3. Import your final exported HDR video that you want to upload to YouTube, place it on the timeline, then navigate to the color page.

4. Add a second serial node then on the second node apply the color space transform OFX plugin.

5. Set the Input Color Space to Rec.2020, Input Gamma to ST2084 1,000 nits, Output Color Space to Rec.709 and Output Gamma to Gamma 2.4. If the video was mastered at other than 1,000 nits, change the Input Gamma to reflect that (e.g. ST2084 800 nits).

6. Now you’re ready to make your adjustments in node #1. You can adjust the curves to your liking. You may use the YRGB curves and Lift, Gamma and Gain color wheels. Most primary, non-secondary controls in Resolve are LUT-compliant, so you can dial in the highlights and shadows with the Log wheels, modify the custom tone mapping by dialing in custom Low and High Range settings, adjust saturation using the curves and use the temperature and tint sliders. Do not use any power windows, qualifiers or sharpening. All adjustments need to apply globally to the entire video. Do not use the highlight and shadow sliders either, as they do not work with the LUT.

7. When you’re done, right click on the thumbnail and select Generate LUT 33 Point Cube.

8. Export the LUT to your user folder, making sure it is named HDR_To_SDR_LUT exactly.

The LUT we generated sitting inside the user folder.

9. Remove the added underscore, the 1, the period and the project name (in this case, _1.Criteria).

Now, the Terminal code in the rtf document will link right up to it.

Huge thanks to Aaron Hinton for sharing the workflow!

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