Author Topic: Heads up - dimming issue for HDR videos  (Read 3434 times)

Offline sevenz

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Heads up - dimming issue for HDR videos
« on: April 18, 2019, 21:00 »
*updated with more findings

Fellow OLED/HDR capable display users, heads up. I just discovered this annoying issue when playing some HDR movies on my LG OLED TV. Just wondering if u saw any similar issue too.


Problem statement
I noticed sudden significant dimming of my OLED display in many typical "averagely lighted" scenes. E.g. when the actor is talking in a dim/ averagely lighted up room without much movement. I was shocked as the scenes weren't bright and it didn't have much speculiar highlights. In this case, I noticed it more prominently on these recent movies i watched:
1) Avengers Infinity War (by Tekno) - scene where Vision was talking to Wanda in a room, preventing her to go out.
2) Captain America Civil War (by Tekno) - many scenes, esp when there are lots of subtitles.

After some troubleshoot, the observation of the symptom is - whenever subtitles appeared, it caused the image to dim automatically. When the subtitles disappear (no speech), the exact same image/scene brightens back. But, when the subtitles are switched off, the picture doesn't suffer from this at all.

But it's not all movies. The issue seems to be more significant on certain HDR movies. Current observation is it's more prominent on those that are tone-remapped by tekno, mastered at 4000 nits.

On the normal HDR movies that were not from Tekno, I remember it was less obvious. I will continue to observe further on the other HDR movies.   

Possible cause:
After some research online, I was brought to attention LG has this in-built auto dimming on their OLEDs where international consumers have reported similar issues in certain conditions. 2 types:

1) Auto Brightness Limiter (ABL) -The online findings suggests that this could be causing it as the display tries to limit its brightness in certain conditions. It affects SDR picture too if the luminance exceeds certain nits. This seems like can't be turned off on the LG OLEDs :(

2) ASBL dimming - When display detects a still image played for a certain time, the picture will auto dim too. This potentially affects display calibration and must be careful during calibration to prevent display going into dimming. Luckily, this can be turned off via the service menu :)

More details here from avs forum:
https://www.avsforum.com/forum/40-oled-technology-flat-panels-general/2440714-how-turn-off-asbl-lg-oled-tv-5.html#/topics/2440714?page=1

Owners of HDR-capable displays or OLEDs, do u all see similar dimming issue on your display on some HDR-mastered videos? And what display are u using?

How to test - just play a relatively static scene in a HDR-mastered movie where the person is talking and pausing his speech in a room and the camera focuses on the portrait of the person. Switch on subtitles. Observe what happens when the subtitles appear and disappear.
« Last Edit: April 18, 2019, 22:58 by sevenz »

Offline YANG

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Re: Heads up - dimming issue for HDR videos
« Reply #1 on: April 18, 2019, 21:16 »
without engaging HDR,when watching non-HDR content like movies from DVD,I'll hv to brighten up to get some details from dark scenes。
however,some movies can benefit from HDR & some don't。that may dependent on the age of the movie when it was made。taking Last of the Mohicans vs Revenant vs the Patriot,the last 2 on non-HDR mastered DVD can benefit from post HDR process,but LotM cant。

Offline desray

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Re: Heads up - dimming issue for HDR videos
« Reply #2 on: April 18, 2019, 22:32 »
Fellow OLED/HDR capable display users, heads up. I just discovered this annoying issue when playing HDR movies.

I recently started playing HDR movies (remapped by tekno) on my LG oled TV, and evaluating the HDR PQ.

I noticed sudden significant dimming of my OLED display in many typical "averagely lighted" scenes. E.g. when the actor is talking in a room without much movement. I was shocked as the scene wasn't bright and it didn't have much speculiar highlights

Did some investigation. I discovered that whenever the subtitles appeared, it caused the image to dim automatically. When the subtitles disappear (no speech), the exact same image/scene brightens back.

When subtitles are switched off, the picture doesn't suffer from this at all.

After some research, I was brought to attention LG has this in-built auto dimming on their OLEDs. 2 types.

1) Auto Brightness Limiter (ABL) -The online findings suggests that this could be causing it as display tries to limit its brightness in certain conditions. It affects SDR picture too if the luminance exceeds certain nits. This seems like cant be turned off on LG OLEDs :(

2) ASBL dimming - When display detects a still image played for a certain time, the picture will auto dim too. This potentially affects display calibration and must be careful during calibration to prevent display going into dimming. Luckily, this can be turned off via the service menu :)

More details here from avs forum:
https://www.avsforum.com/forum/40-oled-technology-flat-panels-general/2440714-how-turn-off-asbl-lg-oled-tv-5.html#/topics/2440714?page=1

Owners of a HDR capable TVs or OLEDs, do u all see similar dimming issue on your display on HDR-mastered videos? And what display are u using?

How to test - just play a relatively static scene in a HDR-mastered movie where the person is talking in a room and the camera focuses on the portrait of the person. Switch on subtitles. Observe what happens when the subtitles appear and disappear.

Good sharing of your experience with bros here. :)

Offline rockzilla

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Re: Heads up - dimming issue for HDR videos
« Reply #3 on: April 18, 2019, 22:51 »
*updated with more findings

Fellow OLED/HDR capable display users, heads up. I just discovered this annoying issue when playing some HDR movies on my LG OLED TV. Just wondering if u saw any similar issue too.

But it's not all movies. The issue seems to be more significant on certain HDR movies. Current observation is it's more prominent on those that are tone-remapped by tekno, mastered at 4000 nits.

Problem statement is - I noticed sudden significant dimming of my OLED display in many typical "averagely lighted" scenes. E.g. when the actor is talking in a dim/ averagely lighted up room without much movement. I was shocked as the scenes weren't bright and it didn't have much speculiar highlights. In this case, I noticed it more prominently on:
1) Avengers Infinity War (by Tekno) - scene where Vision was talking to Wanda in a room, preventing her to go out.
2) Captain America Civil War (by Tekno)

Did some investigation. I discovered that whenever the subtitles appeared, it caused the image to dim automatically. When the subtitles disappear (no speech), the exact same image/scene brightens back. But, when subtitles are switched off, the picture doesn't suffer from this at all.

It was less obvious on the normal HDR movies that were not re-tone-mapped.

After some research, I was brought to attention LG has this in-built auto dimming on their OLEDs. 2 types:

1) Auto Brightness Limiter (ABL) -The online findings suggests that this could be causing it as the display tries to limit its brightness in certain conditions. It affects SDR picture too if the luminance exceeds certain nits. This seems like can't be turned off on the LG OLEDs :(

2) ASBL dimming - When display detects a still image played for a certain time, the picture will auto dim too. This potentially affects display calibration and must be careful during calibration to prevent display going into dimming. Luckily, this can be turned off via the service menu :)

More details here from avs forum:
https://www.avsforum.com/forum/40-oled-technology-flat-panels-general/2440714-how-turn-off-asbl-lg-oled-tv-5.html#/topics/2440714?page=1

Owners of a HDR capable TVs or OLEDs, do u all see similar dimming issue on your display on some HDR-mastered videos? And what display are u using?

How to test - just play a relatively static scene in a HDR-mastered movie where the person is talking and pausing his speech in a room and the camera focuses on the portrait of the person. Switch on subtitles. Observe what happens when the subtitles appear and disappear.

Had this issue as well, so far i had to turn off the subtitle to overcome it.

Offline sevenz

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Re: Heads up - dimming issue for HDR videos
« Reply #4 on: April 18, 2019, 22:55 »
Had this issue as well, so far i had to turn off the subtitle to overcome it.

Thanks for the inputs rockzilla! Possible to share which display u are using?

Offline ronildoq

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Re: Heads up - dimming issue for HDR videos
« Reply #5 on: April 19, 2019, 09:42 »
Oh so it’s thesubtitles ! I have a similar issue when watching YouTube, it sorts of auto DIM, so now I know it’s due to the subtitles / caption setting on YouTube

Great info

Offline desray

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Re: Heads up - dimming issue for HDR videos
« Reply #6 on: April 19, 2019, 10:38 »
Oh so it’s thesubtitles ! I have a similar issue when watching YouTube, it sorts of auto DIM, so now I know it’s due to the subtitles / caption setting on YouTube

Great info

Local dimming in TV is akin to the Dynamic IRIS (DI) implementation in a Projector. Projector owners tends to see this fluctuation between "dimming and illuminating" more noticeably due to the enlarged screen size, hence more pronounced in a way but it will never quite get to the extent of being too "distracting" since Projector does not employ local dimming as it is projected as one single image on to the screen. The anomaly as a result of DI is fleeting "flickering" in light modulation for some projectors with too "aggressive" DI just like the older JVC generation projectors.

But I didn't actually expect OLED TV with smaller screen size with local dimming been plagued by it. The only benefit of DI in projector or local dimming in TV is to get the best "dynamic" Contrast and black levels out of the picture.
« Last Edit: April 19, 2019, 10:42 by desray »

Offline ronildoq

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Re: Heads up - dimming issue for HDR videos
« Reply #7 on: April 19, 2019, 11:50 »
Local dimming in TV is akin to the Dynamic IRIS (DI) implementation in a Projector. Projector owners tends to see this fluctuation between "dimming and illuminating" more noticeably due to the enlarged screen size, hence more pronounced in a way but it will never quite get to the extent of being too "distracting" since Projector does not employ local dimming as it is projected as one single image on to the screen. The anomaly as a result of DI is fleeting "flickering" in light modulation for some projectors with too "aggressive" DI just like the older JVC generation projectors.

But I didn't actually expect OLED TV with smaller screen size with local dimming been plagued by it. The only benefit of DI in projector or local dimming in TV is to get the best "dynamic" Contrast and black levels out of the picture.

Oh thanks for the info, that explains. wasnt aware of all these . But I noticed the dimming on you tube cos I use subtitles on for YouTube . But no such issues for movies and Tekno3d file playbacks . Sevenz is right, now that he mentions it, I can recall having seen this dimming effect

But I don’t such bright subtitles issues after calibration on HDR, I use a warmer setting on the OLED plus I have biased lights, maybe that’s why it helped with the overall experience

Offline desray

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Re: Heads up - dimming issue for HDR videos
« Reply #8 on: April 19, 2019, 11:52 »
Oh thanks for the info, that explains. wasnt aware of all these . But I noticed the dimming on you tube cos I use subtitles on for YouTube . But no such issues for movies and Tekno3d file playbacks . Sevenz is right, now that he mentions it, I can recall having seen this dimming effect

But I don’t such bright subtitles issues after calibration on HDR, I use a warmer setting on the OLED plus I have biased lights, maybe that’s why it helped with the overall experience

Yes, that does help.



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Offline sevenz

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Re: Heads up - dimming issue for HDR videos
« Reply #9 on: April 19, 2019, 12:56 »
I briefly ran thru a few "normal" HDR movies, with average lighted similar scenes, e.g. like in a room, actors having convo. The dimming issue, wasn't 100%.

Some movies ok. Some had dimming on certain scenes with subtitles on, although much less pronounced. I noticed that those that didn't have issues, the subtitles were less bright/ illuminated.

But the 2 Tekno-mastered movies i watched, somehow the subtitles were SUPER BRIGHT. So that made the dimming super obvious.

HDR seems like treating the white subtitles like any other small white speculiar highlight in the picture. So, I wonder, if the movie is mastered at 10,000/ 4000 nits, does it mean the white in the white subtitles will also be brighter compared to one that is mastered at lower light output target like 1,000 nits? If yes, it could explain why this symptom is much more prominent on the Tekno files that are mastered at 4000 nits.

As for ABSL, I disabled the ASBL on my display via service menu and it made calibration process better. Cos previously sometimes, during calibration, the gamma would suddenly drop/change. Now more stable.

« Last Edit: April 19, 2019, 13:39 by sevenz »

Offline rockzilla

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Re: Heads up - dimming issue for HDR videos
« Reply #10 on: April 19, 2019, 16:34 »
When i encounter the issue, i did some searching. It appear that it affected both qled and oled and various brands, no fix at the moment.

Some mentioned go into admin mode to disable local dimming, some disable subtitle, and some change the subtitle color. I personnel choice is still disable subtitle as the result is more constant.

Offline ronildoq

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Re: Heads up - dimming issue for HDR videos
« Reply #11 on: April 20, 2019, 10:03 »
I briefly ran thru a few "normal" HDR movies, with average lighted similar scenes, e.g. like in a room, actors having convo. The dimming issue, wasn't 100%.

Some movies ok. Some had dimming on certain scenes with subtitles on, although much less pronounced. I noticed that those that didn't have issues, the subtitles were less bright/ illuminated.

But the 2 Tekno-mastered movies i watched, somehow the subtitles were SUPER BRIGHT. So that made the dimming super obvious.

HDR seems like treating the white subtitles like any other small white speculiar highlight in the picture. So, I wonder, if the movie is mastered at 10,000/ 4000 nits, does it mean the white in the white subtitles will also be brighter compared to one that is mastered at lower light output target like 1,000 nits? If yes, it could explain why this symptom is much more prominent on the Tekno files that are mastered at 4000 nits.

As for ABSL, I disabled the ASBL on my display via service menu and it made calibration process better. Cos previously sometimes, during calibration, the gamma would suddenly drop/change. Now more stable.

Though mastered in 4K or 10k nits, it will still be down to hardware specs to produce the peak luminance, in the case of the C7 the peak luminance is about 700nits only. It will not possibly hit 4000 nits. So far only the new Sony display is capable of 10,000 nits

Install the bias lights, that will help. There is remote where u can adjust the dim settings of the bias lights, that will help your eyes fatigue

Another option is to use grey subtitles , that should avert the problems as highlighted above

Finally, go with the OLED light that suits your taste. Don’t have to follow what the experts advice, follow what u think is right for your eyes, that is the most important thing. The reading is for your knowledge.

You calibrate to reference, then tweak to preference , that’s how u should approach every calibration, be it video or audio. Otherwise your journey never ends and u end up busy calibrating but not enjoying the moment. Time to pop in those HDR tekno movies and start enjoying ! It’s been almost a year now since u have owned the OLED , really should be enjoying the full benefits of HDR on the OLED

Offline desray

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Re: Heads up - dimming issue for HDR videos
« Reply #12 on: April 20, 2019, 10:25 »
Though mastered in 4K or 10k nits, it will still be down to hardware specs to produce the peak luminance, in the case of the C7 the peak luminance is about 700nits only. It will not possibly hit 4000 nits. So far only the new Sony display is capable of 10,000 nits

Install the bias lights, that will help. There is remote where u can adjust the dim settings of the bias lights, that will help your eyes fatigue

Another option is to use grey subtitles , that should avert the problems as highlighted above

Finally, go with the OLED light that suits your taste. Don’t have to follow what the experts advice, follow what u think is right for your eyes, that is the most important thing. The reading is for your knowledge.

You calibrate to reference, then tweak to "preference", that’s how u should approach every calibration, be it video or audio. Otherwise your journey never ends and u end up busy calibrating but not enjoying the moment. Time to pop in those HDR tekno movies and start enjoying ! It’s been almost a year now since u have owned the OLED , really should be enjoying the full benefits of HDR on the OLED

Bro, sorry I have to disagree with you on the part of the video calibration (too generalized). While I wholeheartedly agreed on the audio part (sound is subjective) but the basis of video calibration is to get to the reference levels cannot be downplayed...what else is the primary purpose if not to get as close to the reference as possible? YOne should refrain from increasing the colors, tint, saturation or even the gamma settings AFTER you already got the reference levels right. Video unlike Audio, it is well documented and can be followed as far as REC709 is concerned. The recent issue is the introduction of HDR content and the ability of the display to output HDR content at it optimum setting (nits vs nits). No matter how we are going to view this HDR thing, some form of tone-mapping (which is also a form of compression) will have to be performed either at the source (4K UHD bluray player) or at the display end (TV or Projector). For HDR purist, Projector is and will NEVER be the way to go (at least for now) if you want that glorious bright picture image simply because the current light engine is unable to reproduce that amount of light source to bring out the best in HDR imagery. So the only way is still TV be it OLED or any equivalent form of technology. HDR calibration is a bit problematic as we delve further into the WCG and the use of ST2084 (different variant of measuring gamma)...this is where the problem comes in, some of the COTS colorimeter is either good at picking up colors or light but never good at both. Unlike REC 709, this is alot easier when we only use BT.709 colors and a constant gamma (2.0, 2.2, 2.3, 2.4 etc). For HDR, we can only opt for color accuracy or gamma accuracy...and I'll choose the latter any time for the simple reason - we need both low and high end of the IRE measures to be "clean" as possible. Colors will always be at least a DCI-P3 which almost guarantee a wide color gamut spectrum compared to BT.709.

In summary, we should as far as possible, try to get to the reference levels for video calibration...it is not a matter of preference but how far can we get to the reference.
« Last Edit: April 20, 2019, 10:29 by desray »

Offline ronildoq

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Re: Heads up - dimming issue for HDR videos
« Reply #13 on: April 20, 2019, 10:44 »
Yes desray, I think you r right. Otherwise everyone will have their version of blue. This I agree, all has to be calibrated to reference. No doubt

But it seems that with the current HDR standard, even measuring the gamma is not really reference stuff. The correct method would be to use the EOTF target curve, as the reference. When software like chromapure don’t provide such a workflow, how do one go ahead and calibrate HDR to gamma targets and called it reference ?

Yea you can get close to reference, but that’s still not reference. It’s still preference, which is as close to reference.

And for the C7, there is definitely no way to calibrate to reference for HDR, it’s more to LG’s reference

Offline sevenz

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Re: Heads up - dimming issue for HDR videos
« Reply #14 on: April 20, 2019, 14:36 »
Though mastered in 4K or 10k nits, it will still be down to hardware specs to produce the peak luminance, in the case of the C7 the peak luminance is about 700nits only. It will not possibly hit 4000 nits. So far only the new Sony display is capable of 10,000 nits

Install the bias lights, that will help. There is remote where u can adjust the dim settings of the bias lights, that will help your eyes fatigue

Another option is to use grey subtitles , that should avert the problems as highlighted above

Finally, go with the OLED light that suits your taste. Don’t have to follow what the experts advice, follow what u think is right for your eyes, that is the most important thing. The reading is for your knowledge.

You calibrate to reference, then tweak to preference , that’s how u should approach every calibration, be it video or audio. Otherwise your journey never ends and u end up busy calibrating but not enjoying the moment. Time to pop in those HDR tekno movies and start enjoying ! It’s been almost a year now since u have owned the OLED , really should be enjoying the full benefits of HDR on the OLED

Thanks bro! Haha, already enjoying keke. Slowly. Cos only can watch when baby is out of house. The colors, details & tone mapping from tekno files is syok. Love it.

But I'm still playing around to see what's best and won't affect the intended HDR PQ, esp the tone mapping and minimise errors in colour/gamma. Cos i want the pq to be as near to the intended standards as possible

This HDR thing is a pain, cos the more I read about it, the standards are not very standardised lol. I wonder what do calibration developers or calibrators feel about it. Will it be a pain and headache to them? Haha

I did try diff colour subtitles. It helped a bit but still affects dimming. So the best workaround for me is to - disable subtitles :)

I don't think bias lights will work for my eyes as i find it makes my viewing unnatural ie. have lights surrounding my display when watching. So still trying to read up more to see what can be done.

I did try adjusting OLED light B4, which did help reduce glare to my eyes. But the problem is - after some research online, the expert video calibrators who had calibrated OLEDs advise to leave oled light and contrast at 100. If we touch it, their inputs was that it affects the intended HDR tone mapping logic and screw up the colors. Ya, great right ....? I was like "then how?" 

Sigh. I wonder if enough thought had gone thru the whole HDR development

 
« Last Edit: April 20, 2019, 14:37 by sevenz »

 

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