Dolby Vision brightness bug when tone mapping

[Mahinepua 81]

Hi on the new windows app I’m experiencing the same issue as hdr which was addressed by…hdr-compute-peak=no

Is there a similar option for Dolby Vision titles? Some have distracting brightness changes every few seconds.

It would also be a good idea to disable dv and fallback to hdr on hybrid movies as Emby prefer dv.

 

Edited January 18, 2025 by Mahinepua

[Mahinepua 81]

As its no longer possible to edit mpv.conf Emby is going to need to add settings regularly to fix these issues or reenable mpv.conf like the jellyfin player has an option for.

[Mahinepua 81]

This could be a gpu-next bug.

https://github.com/mpv-player/mpv/issues/10824

 

[softworkz 5066]

Does this happen as well with the original mpv.dll or only with your custom version?

 

[Mahinepua 81]

With the original, custom and even standalone mpv.

[softworkz 5066]

Can you try with settings like this?

[Mahinepua 81]

Tried that last night with generiq, didn’t fix it.

[Mahinepua 81]

I might try with gpu-next disabled when the wife isn’t watching a movie and see if it makes a difference.

[Mahinepua 81]

Some of these setting might also help…

Those three parameters are what are really doing the trick to the very good SDR representation of MPV:

--hdr-compute-peak=<auto|yes|no>
Compute the HDR peak and frame average brightness per-frame instead of relying on tagged metadata. These values are averaged over local regions as well as over several frames to prevent the value from jittering around too much. This option basically gives you dynamic, per-scene tone mapping.

--hdr-peak-decay-rate=<1.0..1000.0>
The decay rate used for the HDR peak detection algorithm (default: 100.0). This is only relevant when --hdr-compute-peak is enabled. Higher values make the peak decay more slowly, leading to more stable values at the cost of more "eye adaptation"-like effects (although this is mitigated somewhat by --hdr-scene-threshold). A value of 1.0 (the lowest possible) disables all averaging, meaning each frame's value is used directly as measured, but doing this is not recommended for "noisy" sources since it may lead to excessive flicker. (In signal theory terms, this controls the time constant "tau" of an IIR low pass filter)

--hdr-scene-threshold-low=<0.0..100.0>, --hdr-scene-threshold-high=<0.0..100.0>
The lower and upper thresholds (in dB) for a brightness difference to be considered a scene change (default: 5.5 low, 10.0 high). This is only relevant when --hdr-compute-peak is enabled. Normally, small fluctuations in the frame brightness are compensated for by the peak averaging mechanism, but for large jumps in the brightness this can result in the frame remaining too bright or too dark for up to several seconds, depending on the value of --hdr-peak-decay-rate.

Edited January 18, 2025 by softworkz
Fixed appearance on light theme

[Mahinepua 81]

Apologies Softworkz it was bt.2446a I tried last night.

Just tried bt.2390 and the issue is fixed!

Returning the tone mapping mode to auto and the problem is back.

Should I leave the setting on bt.2390 for all media or does the auto setting behaviour need modifying to fix this in the next release?

Thanks for your help, good guess

[Mahinepua 81]

Just checked again and brightness still changes but it’s not as bad as before.

Will test some other tonemapping modes.

Edited January 19, 2025 by Mahinepua

[Mahinepua 81]

I’ve tested hable, gamma, linear, 2446a, 2094-40 with Avengers and Allied both Dolby Vision.

All exhibit noticeable brightness changes on my test scenes.

BT.2390 is by far the best setting, brightness changes are subtle and the average viewer wouldn’t notice. Tone-mapping looks excellent to my untrained eyes for both hdr & dv.

Not all media is affected, both test movies are dv profile 8.1 but other similar profile movies are fine.

I’m going to leave tonemapping set to 2390 and consider the issue resolved in my case.