Mpv: How to play HDR videos on a SDR screen?

[JulianLai]

Do I have to setup something, or just play it?

mpv version and platform

mpv git-aae0833fc6 (C) 2000-2017 mpv/MPlayer/mplayer2 projects
built on Sat Mar 25 13:03:09 CST 2017
ffmpeg library versions:
libavutil 55.34.101
libavcodec 57.64.101
libavformat 57.56.101
libswscale 4.2.100
libavfilter 6.65.100
libswresample 2.3.100
ffmpeg version: 3.2.4

[wiiaboo]

Just play it.

[Hrxn]

Yes, you can just play it, but you won't see "real" HDR. Only with a display capable of HDR.

[haasn]

(What happened to just trying it and seeing if it works?)

[ghost]

With HDR, nobody knows whether the result looks correct. This means an expert has to be consulted.

[JulianLai]

@haasn @wm4 @Hrxn @wiiaboo It looks so dark.

[wiiaboo]

Try different values of --target-brightness and the next two options. There's no correct way of displaying HDR on SDR.
I use

target-brightness=120
hdr-tone-mapping=reinhard

[JulianLai]

@wiiaboo The graphic looks brighter, but the subtitle still looks so dim.

[wiiaboo]

If this is an image-based subtitle format (DVD or BD), there's nothing you can do about it, other than OCR'ing them.

[ghost]

Do you have a sample for HDR + image subtitles?

[JulianLai]

@wiiaboo @wm4 Yes, it is the image-based subtitle, after I change it to the SRT format, the problem is solved. Thanks!

Which target brightness do you guys prefer? 100 looks much better for me.

[wiiaboo]

Apparently if you use blend-subtitles=yes or blend-subtitles=video it'll use the same hdr-tone-mapping as the video, so that could make them brighter too.

[kkkrackpot]

JulianLai

Which target brightness do you guys prefer? 100 looks much better for me.

AFAIK, it's not a question of _prefer_. Every TV has its own peak brightness that can be measured with special tools (a colorimeter or something). That is if you want a "correct" tone-mapping.
Also it's possible to find some "average" brightness for some models in reviews, etc.
Otherwise you can set any target brightness you feel better with.
PS. You might want to read this thread too https://github.com/mpv-player/mpv/issues/2572

[haasn]

I guess image-based subtitles should probably be treated the same way as the OSD, and not like part of the video (unlike e.g. ASS subtitles)

[JulianLai]

@haasn @wiiaboo @wm4 By the way, can't I adjust the target-brightness with vaapi on AMD RX460?