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Old 20th November 2017, 08:25   #1  |  Link
mmace
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HEVC HDR to x264 8 bit non-hdr

Hi guys, apologies if this is the wrong sub-forum but I'm hoping for some help...
I have some UHD HDR movies (seem to be the only ones available in UHD) that are in x265/HEVC. I need to transcode to x264 (hardware not fast enough for HEVC) and I also need to make them non-HDR as my UHD TV isn't HDR and my players (PC, Android and the TV itself) show the videos as very washed out with barely any colour.

I've been using handbrake to transcode HEVC to x264 but I'm not sure of the best way to do this, can anyone advise?

Thank you
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Old 20th November 2017, 16:58   #2  |  Link
kamivh1
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this is my problem too
can anyone help??
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Old 20th November 2017, 19:20   #3  |  Link
x265_Project
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HDR content has a different color space (ITU-R Recommendation 2020) than SDR (ITU-R Recommendation BT.709). Encoders (x264 or x265, for example) don't do any color space conversion.
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Old 20th November 2017, 19:43   #4  |  Link
Selur
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iirc MPC-HC has an option to playback HDR on non-HDR displays, may be someone can create a Vapoursynth/Avisynth filter that does the same,... but I agree this is not something that should be part of the encoder itself
HDR10 -> SDR: https://forum.doom9.org/showthread.php?p=1800675
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Old 20th November 2017, 21:32   #5  |  Link
excellentswordfight
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The biggest problem is not the color space but the transfer curve. HDR10 (e.g) is graded way differently than SDR-material so you need apply something like a LUT to convert it for it to look OK with a normal transfer curve. I have tried a few, with acceptable results, but never got the tonal curve/contrast before and after to be simulair enough for my taste.

It would be very nice to get the conversion method from madVR as a standalone filter (for avisynth or similar), the method used there is way better then anything I have tried at least.

Last edited by excellentswordfight; 20th November 2017 at 21:40.
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Old 20th November 2017, 22:52   #6  |  Link
nevcairiel
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Quote:
Originally Posted by x265_Project View Post
HDR content has a different color space (ITU-R Recommendation 2020) than SDR (ITU-R Recommendation BT.709). Encoders (x264 or x265, for example) don't do any color space conversion.
Thats quite the generalization. BT.2020 is not exclusive to HDR, any UHD content can/should use it, although some UHD stuff is still encoded in "legacy" 709.

There is still quite the conversion to be done from HDR to SDR, but you don't necessarily have to convert away from BT.2020.
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Old 21st November 2017, 02:49   #7  |  Link
Asmodian
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Is there anything in avisynth or vaporsynth that can do an HDR to SDR conversion? I have HD versions of everything I have UHD HDR copies of (HD+UHD combo editions) but I wouldn't know where to start if I wanted to even directly transcode a UHD HDR blu-ray without any conversions, let alone convert HDR to SDR.

BT.2020 to BT.709 is easy, it is preserving the metadata or doing the HDR or SDR tone mapping using it that I have no idea how to do.
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Old 10th December 2017, 16:39   #8  |  Link
Yoshi
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What would already help would be a possibility to feed some H.264 encoder with madVR's output as its results in terms of HDR->SDR conversion including dithering should be more than decent to start any encoding process with.

Hence the question to everyone: any tool around which is able to capture a player's output in conjunction with madVR and feeding that to let's say x264?
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Old 13th December 2017, 16:37   #9  |  Link
zub35
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You can try using software for screen capture the stream issued by madVR in lossless compress, and then compress it into x264.
While this is the only quality way ... alas.

HDR - madVR - screen_capture (lossless or crf<10) - x264 (SDR)

Last edited by zub35; 13th December 2017 at 22:10.
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