Trying to understand HDR playback in Emby Theater

[frankmb 27]

I'm trying to understand HDR playback in Emby Theater.

I have a TCL 55S425 Roku TV that is 4K and supports HDR

If I play a 4k HDR episode:

1: in the Emby Roku app everything in fine. I see the HDR logo appear on the top right of my screen that indicates HDR playback.

2: In Windows 10, for some reason I can't output in HDR. This is not a Emby issue, but I'm stuck with SDR color.

2.1: If I play in the web app, it transcodes and I get washed out colors. I know this is what I should expect because Emby doesn't support this well.

2.2: If I play in Emby Theater with transcoding, I get washed out color. This is expected.

2.3: If I play in Emby Theater without transcoding, I actually get good colors! What is happening here? Is mpv doing some sort of magic with the colors? 

[sooty234 266]

Ha! Let me see if I can clarify this, for you.

The magic auto HDR switching from SDR to HDR in Win 10, is all but dead. You need to manually turn on HDR in Windows, then mpv will pass the metadata to your TV. If you don't turn on HDR in Window, mpv will tone-map the metadata, which will also give a good quality output. But most people want to see the automatic HDR popup on their display. You won't get that as HDR will always be enabled. VLC does the same thing. You can blame Microsoft, they've pretty much killed it. But running in HDR is actually really good these days. Mine is configured this way. And depending on what GPU you have, some adjustments can also be made, using an mpv.conf.

I hope this helps  

[frankmb 27]

Thanks yeah this helps. So mpv can do tone-mapping and that is what I'm seeing.

I tried to enable HDR in Windows it doesn't work. Windows says my display doesn't support HDR. This might be because I'm using a Displayport to HDMI adapter (active). The computer doesn't have any HDMI output. I get 4k 60 Hz, just not HDR so I don't mind too much.

[sooty234 266]

If it's a DisplayPort 1.2, Windows won't accept that. It has to be 1.4, and you'll need the correct corresponding adapter (DP 1.4 to HDMI 2.0). Windows is horribly picky about that.

[SLMK 13]

I cant be the only one who finds turning HDR on in windows makes SDR content (particularly youtube videos) look like crap no matter what you do? Its so bad that enabling HDR in windows is simply not an option for me. It looks like Emby will never support auto switching like MadVR for various reasons, which leaves it completely useless for HDR for me.

Its a really shitty situation. I know this is not all Embys fault, Microsoft should be ashamed of the state of their HDR support, but it still leaves me looking at dumping Emby theatre as it cant do the job properly.

Is there some tweak Ive missed that will make SDR content not look like complete shit with the HDR toggle enabled? Because losing the ability to watch video content outside of emby is not a good tradeoff for having HDR on. I can just play HDR videos up in MPC with MadVR and not have any of these problems, but as the amount of HDR content increases this is becoming a more and more annoying workaround.

[sooty234 266]

What GPU do you have? And can you describe what you think is bad with the picture in youtube?

[SLMK 13]

1050ti.

Playing around with the HDR brightness slider I can get the desktop and colours to look ok, still different, but not necessarily worse. The big issue for me is that deep shadows in youtube content get crushed to hell and become very blocky, they look fine with the HDR toggle off. I haven't succeeded in finding a balance of settings where HDR is on, but SDR shadows aren't blocky garbage.

[sooty234 266]

How have you configured your colorspace in the Nvidia control panel? Can you post a screenshot of the blockiness? Are your drivers up to date? If you aren't gaming, I'd suggest using the studio drivers.

[frankmb 27]

@SLMK What is the peak brightness of your display?

 

I've been comparing the same episode in SDR and HDR on my TCL 55S425 Roku TV. This TV is pretty cheap and has low peak brightness. I now think this causes the HDR version to be worse than SDR as low brightness parts of the image are too dark in the HDR version. I am testing on the Emby Roku app, Not on Windows.

I found this article discussing this: https://www.forbes.com/sites/johnarcher/2019/11/27/the-one-killer-reason-why-buying-a-bargain-bucket-tv-on-black-friday-is-a-terrible-idea/?sh=139340937e88

[SLMK 13]

On 11/25/2020 at 3:24 PM, sooty234 said:

How have you configured your colorspace in the Nvidia control panel? Can you post a screenshot of the blockiness? Are your drivers up to date? If you aren't gaming, I'd suggest using the studio drivers.

Ill look into those when I get a chance. Drivers are about 6 months old, not regularly updated as I'm using the transcode limit hack.

[SLMK 13]

4 hours ago, frankmb said:

@SLMK What is the peak brightness of your display?

 

I've been comparing the same episode in SDR and HDR on my TCL 55S425 Roku TV. This TV is pretty cheap and has low peak brightness. I now think this causes the HDR version to be worse than SDR as low brightness parts of the image are too dark in the HDR version. I am testing on the Emby Roku app, Not on Windows.

I found this article discussing this: https://www.forbes.com/sites/johnarcher/2019/11/27/the-one-killer-reason-why-buying-a-bargain-bucket-tv-on-black-friday-is-a-terrible-idea/?sh=139340937e88

Sony X900F
Brightness	482 cd/m2
Peak brightness (HDR)	1020 cd/m2 (10% window)