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Post #1416839

Author
44rh1n
Parent topic
Info: Guide for Working with 4K HDR Blu-ray Rips in SDR
Link to post in topic
https://originaltrilogy.com/post/id/1416839/action/topic#1416839
Date created
12-Mar-2021, 12:50 AM
Last modified
25-Mar-2021, 2:10 PM
Edited by
44rh1n
Reason for edit
None provided

winoni71 said:
My head hurts, this is very confusing.
If there’s no metadata, then how can each scene be graded differently and why is it so difficult to make a conversion to SDR?

Metadata, or the lack thereof, has nothing to do with one’s ability to grade each shot of a film differently from the next.

The reason you’ll likely need to make adjustments on a shot-by-shot basis is because HDR (Rec.2020/ST.2084) has a completely different color space and gamma than SDR (Rec.709/Gamma 2.4). There’s no one-size-fits-all approach to a downconversion. They’re entirely different formats, with entirely different ranges of color and luminance. So you’re likely never going to find a one-click solution that’s perfect.

winoni71 said:
I’m not looking to make a restoration, but to have an “all-purpose” method to convert HDR to SDR while preserving (as much as possible, without grading scene by scene) the visual characteristics, I’m not looking for perfection.

If you’re looking for an easy solution that doesn’t involve performing shot-by-shot corrections, then you can use a Color Space Transform effect (as illustrated in this tutorial above), a LUT, or you can do the method that another user above suggested in Premiere. Just know that it’s a technical conversion, not a creative one. So while it’s an accurate HDR-To-SDR conversion, it might not always look how you want it to look.

If you’re not doing fan restorations / preservations, then might I ask why you’re interested in doing this in the first place? Wouldn’t it just make more sense to buy the 1080p SDR versions of the movies you want to watch? Or better, get a 4K Blu-ray player? (If you have the funds, that is.)

winoni71 said:
Knowing this, having at my disposal both Abode Premier PRO and Resolve Studio, what would you recommend to achieve what I’m looking for?

Thank you.

If you have Resolve Studio (the PAID version of Resolve), then I would recommend trying out the automatic Dolby Vision trim analysis. This will do an automatic per-shot conversion from HDR to SDR. So rather than a single one-size-fits-all approach, it will treat each shot individually.

1). Bring the film into the Media Pool (you’ll get much faster performance if you convert to ProRes first, as illustrated in the tutorial at the beginning of this thread. But if you have a fast computer then the original HEVC should work).

2). Go to your Project Settings and change the Color Management timeline color space to Rec.2100 ST.2084. Then check the “Enable Dolby Vision” checkbox.

**Important: Ensure “Mastering Display” is set to “1000-nit, BT.2020, D65, ST.2084, Full.” That is the correct option for most 4K Blu-rays. However, for some 4K Blu-rays that are mastered at 4000-nits, you’ll want to select the “4000-nit, BT.2020” option. ALSO: make sure the resolution and framerate are correct in the the Master Settings.

3). Add the film to a new timeline (make sure the timeline has the same framerate and resolution as your movie). The image should look flat and ugly on an SDR GUI display.

4). On the Edit page, select the movie in the timeline and then go to menu item “Timeline > Detect Scene Cuts.” This will take a while, but it will analyze the movie and make physical cuts to every cut in the film. Once it’s done, scrub through to make sure it didn’t add cuts where it shouldn’t have.

5). Navigate to the Color page and click on the Dolby Vision button on the bottom left region of the screen (the button won’t be there unless you enable Dolby Vision, as mentioned in step 2).

6). Ensure the Target Display Output is set to “100-nit, BT.709, BT.1886, Full.”

7). Click Analyze All. (And leave Enable Tone Mapping Preview selected). Once it’s done, you’ll notice that the image no longer looks flat and ugly because you’re now seeing the SDR version created by the Dolby Vision analysis.

**Important: If the movie is wider than 16x9 (includes black bars), then the black will need to be excluded from the output, otherwise the black in every scene will skew the analysis. This can be done by selecting Timeline > Output Blanking. There are some great presets for different aspect ratios. If none of those presets are correct for your film, you can create custom Output Blanking by navigating to the “Sizing” button in the middle-right of the GUI, changing the dropdown menu to “Output Sizing,” and then you can adjust the “Blanking” sliders. Or you can physically crop the top and bottom of the video by changing the timeline resolution and image scaling settings in the Project Settings.

8). Lastly, go to the delivery page and set whatever export settings you desire (again, I always recommend ProRes, but the settings you would pick depend on your needs). ***Then go to Advanced Settings, and change the Tone Mapping to Dolby Vision. Ensure the selected option under Dolby Vision is “100-nit, BT.709, BT.1886, Full.” Once you’ve got all your export settings enabled and you’ve selected the Dolby Vision tonemapping, you can add the export to your Render Queue and export it out.

Now you’ll have a beautiful SDR version of the film derived from brand new Dolby Vision metadata that you created yourself. 😃

Hope that helps.