I used a GMIC filter to create a LUT file by comparing an HDR image (in avif) to my desired SDR tonemap, as demonstrated in this video https://www.youtube.com/watch?v=y8gDBT8_ALI
I saved to .cube directly from the plugin and then tried applying it with another filter. The result was pretty close to the original. But then I tried embedding this LUT to the HDR video where that image comes from and uploading, - the LUT is being recognized and acted upon by YouTube, but the output is very washed out in both colors and contrast.
Does anyone have experience with this workflow? Could you help me understand why the results don’t carry over to video, and if it can’t be fixed, what other alternative there is to making a LUT specifically with a before & after?
Attached are the following SDR images: 1) source, 2) the output when applying the LUT to the HDR image in G’MIC, 3) the output from YouTube (which I’ve confirmed, does respect embedded LUTs).
If YouTube ‘respects’ embedded LUTs, then perhaps the issue is partly due to the compression YouTube uses to present your video onto their platform, and if you rendered your original HDR video with a compressed and/or lossy codec etc then that could further degrade the original look.
I don’t know what steps you took, but what I would do is use a video editor, for instance, one I often used to use - Shotcut, put the original video without the LUT applied then open up the filters panel and add your LUT via the ‘LUT (3D)’ filter menu, there is not much else you can do with this filter apart from applying it, and hoping it looks right enough ( there are ways to control the intensity of a LUT in Shotcut, but it requires a workaround, pretty straightforward one though…)
Render and export with h264 or vp9 codec, but rather than go with the default settings, click the Advanced box in the Export panel… Enable two-pass encoding (should be a checkbox for this), then, under ‘Codec > Rate Control’ choose Average Bitrate, and for 1080p, something like 10-15 Mbps average can be good enough, for 4k perhaps 35-45 Mbps or thereabouts, then go ahead and render/export it.
Although this might produce a larger sized video and take longer to upload to YouTube, it could soften the impact of their aggressive compression.
