conf for bt.1886, gamma2.2 and hdr because of recent changes

[Obegg]

With recent changes to mpv and specifically this PR
I'm very confused and I lack some key knowledge in order to solve the issue I face.

I'm trying to create a mpv.conf without profiles, that would fit for TVs that for SDR use gamma of bt.1886 and HDR10+, with additional lines of settings for SDR with gamma of 2.2 (that are commented out)
I even tried multiple times to use AI since I can't get my head around it.

What I have now is not perfect but it's something.

target-colorspace-hint-mode=source-dynamic
target-trc=gamma2.2
treat-srgb-as-power22=auto

target-colorspace-hint-mode=source-dynamic = Because I use HDR10+ TV
target-trc=gamma2.2 and treat-srgb-as-power22=auto = Because my TV gamma for SDR is 2.2

Honestly, I don't understand what sRGB is, which is a bit frustrating, considering my TV only has 2 options for gamma (2.2 and bt.1886).
Back to the topic, I would like a mpv.conf that fit both gamma setting (with commented out lines for the other gamma) and HDR10+, without using profiles.
So it would look some thing like:

# HDR10+
target-colorspace-hint-mode=source-dynamic

# If your TV is gamma 2.2 use these:
target-trc=gamma2.2
treat-srgb-as-power22=auto

# if your TV is gamma bt.1886 use these:
# setting 1
# setting 2

So that even if I would like to change between gamma 2.2 and bt.1886 I would just change a setting on the TV and comment out some lines on mpv.conf.

But the current issue I face is in order to use target-trc=bt.1886 I have to use target-colorspace-hint-strict=no which I found to work for SDR, but broken for HDR, when opening a HDR file and viewing stats we see that the transfer for the display is bt.1886, this requires me to create a profile for each, SDR and HDR, which I don't want.

Some more info for those wondering:

NVIDIA Control Panel
Output color format: YcbCr444
Output color depth: 8 bpc
Output dynamic range: Limited

TV Picture Settings
Gamma: 2.2 / bt.1886

[kasper93]

target-colorspace-hint-mode=target
treat-srgb-as-power22=auto

optionally add

target-contrast=

[Obegg]

Thank you for the quick and helpful response.
A few questions if you have the time.

By using target-colorspace-hint-mode=target now when I open stats I see the transfer for the display is bt.1886, not gamma 2.2 even though my TV is set to gamma 2.2.

1. Wouldn't that cause inaccuracies?
2. From that inaccurate stats reading I assume mpv can't know if the TV is using gamma 2.2 or bt.1886, so this means the user has to manually specify using target-trc, right?
3. I just used cycle-values target-trc bt.1886 and auto, while my TV gamma was set to bt.1886 and they all made a change, so doesn't that mean that we have to set target-trc to show best results, because auto is not bt.1886, which is what the transfer for the video and the display is, so what is going on here?
4. How can target-colorspace-hint-mode=target tell that my TV is HDR10+? I assume it can't tell, it will only send HDR10, right? Considering the inaccuracy with the gamma I mentioned I wouldn't be surprised that it will only send HDR10 and not HDR10+.
5. Since mpv shows display transfer as bt.1886 this means I should change the TV gamma to bt.1886, so the content would be accurate, right?
6. target-contrast requires me to know the value, how can I know that without a colorimeter?
7. When setting target-contrast globally on mpv.conf wouldn't that affect SDR and HDR? Inaccuracies with HDR content?

[kasper93]

By using target-colorspace-hint-mode=target now when I open stats I see the transfer for the display is bt.1886, not gamma 2.2 even though my TV is set to gamma 2.2.

For this you can add sdr-adjust-gamma option

From that inaccurate stats reading I assume mpv can't know if the TV is using gamma 2.2 or bt.1886, so this means the user has to manually specify using target-trc, right?

Yes, but at the same time, you can just enable HDR and use =target mode for all content. Then there is no 2.2 or bt.1886. There is only PQ.

How can target-colorspace-hint-mode=target tell that my TV is HDR10+? I assume it can't tell, it will only send HDR10, right? Considering the inaccuracy with the gamma I mentioned I wouldn't be surprised that it will only send HDR10 and not HDR10+.

mpv can only send HDR10. source-dynamic mode sends HDR10 based on HDR10+/DV metadata, but for stability I would just use =target and let mpv handle the tonamapping. But this is personal preference, both modes are valid and depending on hardware will produce different results.

Since mpv shows display transfer as bt.1886 this means I should change the TV gamma to bt.1886, so the content would be accurate, right?

Yes, most likely this is the best bet. Note that you likely see bt.1886, because there you don't use sdr-adjust-gamma, so it gets the source values.

target-contrast requires me to know the value, how can I know that without a colorimeter?

You can check your display review / datasheet, but adjusting contrast value is easy if you look at dark scene and adjust it down to your liking, such as there is not much clipping or lifted blacks.

When setting target-contrast globally on mpv.conf wouldn't that affect SDR and HDR? Inaccuracies with HDR content?

Yes, target contrast affects both, but it affects the target and unless you change the HDR / SDR mode for content, you will have the same target params. If you want to change per content, you can use autoprofile.

[Obegg]

Once again thank you for the quick, detailed and helpful response.

1. Sorry if I repeat myself, I couldn't understand - to simplify my question: TV is now bt.1886, using target-colorspace-hint-mode=target, stats show bt.1886 for display and video, shouldn't I use target-trc=bt.1886? Asking this because it does seem to make a difference when I do cycle-values target-trc bt.1886.
2. While mpv is playing HDR content while windows has not enabled HDR - mpv stats show the display transfer is gamma 2.2, is that intentional? Shouldn't that be bt.1886? Where did gamma 2.2 come from?

[kasper93]

Without sdr-adjust-gamma the target will follow SDR input format, so in your cases bt.1886, while in HDR mode it will do sRGB output which with treat-srgb-as-power22 become gamma 2.2.

If you don't use HDR, you can use target-trc=bt.1886 sdr-adjust-gamma

[Obegg]

The only thing I had to change is treat-srgb-as-power22=no because if you remember the file blacktest.png from the previous issue, some black squares were too dark, so this fixes that for that particular test file, but I think I'll keep the default you mentioned (target-colorspace-hint-mode=target) + treat-srgb-as-power22=no

Thank you.

[Raza-0007]

@kasper93, from reading your responses, I gather that even with the new updates to mpv, using advanced options like target-colorspace-hint-mode, target-trc etc are still optional, and mpv will still determine the best rendering logic for a given display by itself?

I have never used any of these options and mpv has always worked flawlessly with the default rendering settings for all my three displays; laptop's built-in, external monitor and TV.

[kasper93]

In HDR output mode, it should work best without changing any options. In SDR mode the situation is more complex and while we try to make it work best, we don't have information about your display parameters.

[Raza-0007]

Thank you. Since mpv with default settings has been working fine with my SDR displays for many years, so I assume it will continue to work fine. I will of course let you guys know if I encounter any issues. Thank you for the quick response.

[Obegg]

@kasper93

When I apply the following profile:

[BT.1886]
profile-cond = get("video-params/colormatrix") == "bt.709"
treat-srgb-as-power22=no
target-trc=bt.1886
target-contrast=3500

And I view stats, I see that on Display the Transfer is srgb and not bt.1886.
How can I make sure it will show bt.1886 with the settings I provided?

[kasper93]

--target-colorspace-hint-strict=no probably. But with default sdr-adjust-gamma it should follow input transfer. Also it's weird that you are basing transfer setting on colormatrix.

[Obegg]

Thank you!
I'm using video-params/primaries now, thank you.

[Obegg]

treat-srgb-as-power22=no
target-trc=bt.1886
target-contrast=inf
target-colorspace-hint-strict=no

When using cycle-values target-contrast auto inf 3500 multiple times I see no difference at all.
Is it a bug or is it intentional?
@kasper93

[atrxia1]

If you are watching bt.1886 content and you're telling mpv that your display is bt.1886, then changing target-contrast will not have any effect because no gamma adjustment is being performed. Your autoprofile is functionally identical to --sdr-adjust-gamma=auto/no.

[Raza-0007]

I have a question. I have two SDR displays. mpv is mostly on default settings with the following relevant additions:
vo=gpu-next, hwdec=auto, profile-high-quality, dither-depth=auto and video-sync=display-resample

The latest mpv always picks bt.1886 as transfer for almost all the content I throw at it. I am assuming it does this because mpv has determined that this is the best transfer mode for my displays. The only difference is when I play HDR encoded content on my SDR displays, in which case mpv transfers from pq to gamma2.2.

My question is: does the latest mpv do this because it has determined that gamma2.2 is the best option for playing HDR encoded content on my SDR displays or is it being forced to pick gamma2.2?

I ask because I am still using the August 18th version of mpv as my main player, and that version on same settings always picks bt.1886 for all content including HDR encoded content on SDR displays, and though both gamma2.2 and bt.1886 look good, bt.1886 looks more pleasing to the eyes on my SDR displays.

[kasper93]

The latest mpv always picks bt.1886 as transfer for almost all the content I throw at it. I am assuming it does this because mpv has determined that this is the best transfer mode for my displays.

That's because sdr-adjust-gamma is off by default. And it uses source as output.

The only difference is when I play HDR encoded content on my SDR displays, in which case mpv transfers from pq to gamma2.2.

That's because mpv thinks that gamma2.2 is the most correct output for your display.

[Raza-0007]

That's because sdr-adjust-gamma is off by default. And it uses source as output.

After testing on latest mpv, sdr-adjust-gamma on default i.e. "off" gives the best output on my displays (except for that one situation), so I will leave it as is.

.

The only difference is when I play HDR encoded content on my SDR displays, in which case mpv transfers from pq to gamma2.2.

That's because mpv thinks that gamma2.2 is the most correct output for your display.

So the earlier mpv logic where mpv automatically picked bt.1886 was incorrect? Though both bt.1886 and gamma2.2 look good, bt.1886 looks better on my displays. Is there a setting that would force mpv to pick bt.1886 only in this particular situation (HDR content on SDR display), without affecting other situations?