10 replies to this topic

[Marko1305]

Some 4K HDR channels (like Travelxp 4K) use fully white subtitles, which can cause significant blooming on Full Array Local Dimming/Mini LED LCD TVs and potentially lead to burn-in on OLED TVs. A possible solution would be to add an option to change the subtitle color (grey or dark grey would mitigate the issue) on HDR channels or to allow users to adjust the brightness of the white color. If adjusting isn't possible, preconfiguring subtitles to about 50% white, which aligns with HDR standards, could be effective. I understand that this might not be possible for teletext subtitles, but it should be doable for DVB subtitles, especially since yellow is already an available color option, though it doesn't address the issue and doesn't look great.

[DimitarCC]

Its not so easy since dvb subs are graphics. Yellow color is on dvb specs but nothing else....

[Marko1305]

Its not so easy since dvb subs are graphics. Yellow color is on dvb specs but nothing else....

Well if you can change dvb subtitles color from white to yellow why is grey not a possibility?

[DimitarCC]

technically is possible but not so easy like the yellow which is possible by simple changing of the amount of the blue in color palette.

palette[i].r = MAX(MIN(((298 * y            + 460 * cr) / 256), 255), 0);
palette[i].g = MAX(MIN(((298 * y -  55 * cb - 137 * cr) / 256), 255), 0);
palette[i].b = yellow?0:MAX(MIN(((298 * y + 543 * cb  ) / 256), 255), 0);

As you can see making it yellow is simply setting the blue to 0. But making any kind of shades for the colors is not so easy task.

[littlesat]

Usually subtitles are shown relatively short and they change... Why do you have concerns regards to burning in?

 

The 'blooming' is something we cannot do anything about... We do not have a user interface on 4K... + when they send DVB subs in low resolution, we cannot pump it up... Therefore we love more text subtitles we can render ourselves.... To get them sharper we need an algorithm that can make text of the graphics... I know that exists... but it is never 100%.

Edited by littlesat, 18 August 2024 - 16:27.

[Marko1305]

Usually subtitles are shown relatively short and they change... Why do you have concerns regards to burning in?

The 'blooming' is something we cannot do anything about... We do not have a user interface on 4K... + when they send DVB subs in low resolution, we cannot pump it up... Therefore we love more text subtitles we can render ourselves.... To get them sharper we need an algorithm that can make text of the graphics... I know that exists... but it is never 100%.

First of all, I didn't suggest upscaling the subtitles to 4K, as that would be pointless and wouldn't address the issue. Instead, changing the color of DVB subtitles to something like grey or dark grey, or making them more transparent (or dimmer, whichever is easiest), could solve the problem. Since there's already an option for "Use yellow DVB subtitles," I don't see why it wouldn't be possible to offer more color choices, like grey. Edit: I didn't see the reply of Dimitar but I listed other possible solutions.

 

The second part of the suggestion is more challenging to implement: having two different subtitle color options for SDR and HDR content. If it's not possible to have separate options, users would need to manually switch to grey when watching HDR channels and revert to white or yellow for SDR channels. A potential workaround could be selecting a light grey color that slightly reduces blooming on HDR channels while remaining visible on SDR channels, though this is far from ideal.

 

When watching HDR channels, TV channels intentionally use dimmer or grey logos for the exact reason I'm describing. If the logos were fully white, they would pop and shine excessively in the corner. (Unfortunately, Travelxp seems unaware of this common practice, as they have a fully white logo, which is quite glaring. However, reputable TV channels like BBC, Sky Sports, and Eurosport are aware of this and use dimmer logos to prevent this problem.)

Personally, I have a Full Array Local Dimming (FALD) TV, so blooming is a significant issue. I believe most people have FALDs or Mini LEDs because of the disadvantages of OLEDs—namely, their sensitivity, higher cost, and the fact that they're better suited for dark rooms. However, the problem likely still exists on OLEDs as well, since only highlights should use 100% white in HDR mode. Fully white subtitles are too bright and strain the eyes, especially in dark viewing conditions.

What I'm suggesting here could also greatly benefit those who use their Enigma2 for watching HDR movies and TV shows in the local video player, as they face the same issue. (I could be wrong if there is already an option to change the color of SRT subtitles.)

Edited by Marko1305, 18 August 2024 - 21:24.

[Marko1305]

What I mean by blooming:
Full Array Local Dimming (FALD) TVs and Mini LEDs don't have pixel-based control like OLEDs. Instead, they rely on dimming zones. When something is 100% white—in this case, the subtitles—in HDR mode, local dimming aggressively brightens the area because it considers it a highlight on the screen. As a result, the part of the screen around the subtitles also becomes very bright. This spilling of backlight around a bright object is known as blooming.

If the subtitles were grey( or dimmer/ more transparent), they would appear white or slightly grayish (in the hdr mode) with an acceptable brightness level, reducing the blooming effect.

Edited by Marko1305, 18 August 2024 - 21:40.

[DimitarCC]

I am wondering why you not switch to yellow subtitles? They are darker than full white.
Also the risk of burn in is less with qled tvs which are significantly cheaper than oled.
But the point is that subtitles are usually shown for short time and then replaced by another subtitles in opposite to logos. So they should not cause burn in issues. That is what @littlesat said...

[Marko1305]

I am wondering why you not switch to yellow subtitles? They are darker than full white.
Also the risk of burn in is less with qled tvs which are significantly cheaper than oled.
But the point is that subtitles are usually shown for short time and then replaced by another subtitles in opposite to logos. So they should not cause burn in issues. That is what @littlesat said...

Why don't I switch to yellow subtitles? :

First of all they don't fix the issue it just makes a minimal difference and secondly they look very ugly.

The risk of the burn on qleds (Full Array Local dimming / Mini leds) ? :

If you read my text you should have noticed
that I am not afraid of burn ins on my TV. I just mentioned that it could be a problem on the OLEDs and that fully white subtitles are very bad on HDR content regardless of the TV technology.

The problem on my tv as well as every other FALD/ MiniLed TV is forementioned blooming and very over brightened subtitles.

Edited by Marko1305, 18 August 2024 - 21:52.

[Marko1305]

I gave the analogy regarding logos of HDR TV channels, something that all of you could've noticed during these Olympics for example on Eurosport 4k. The logos are grayish/dimmer to address the issue.

The second analogy would be 4K HDR Blu-rays. The subtitles on these Blu-rays must meet specific standards, and one of the criteria is that the white in the subtitles is 50% dimmer for this exact reason.

Edited by Marko1305, 18 August 2024 - 22:03.

[DimitarCC]

i understood all that....But blooming is the same for all HDR sat channels mostly...Just most of them currently have no subtitles.

You can a bit fix the blooming by playing with brightness and contrast of the TV but that is very inconvenient since returning to not HDR channel will produce very ugly picture.

As for subtitles in HDR mode...Well not all boxes have implemented detection of HDR in drivers. So detection of HDR picture in enigma2 will be very unreliable since drivers have to support it (which is not like that always as i mentioned).

So only option is user manually to switch the mode of subtitles. That is also inconvenient if you often switch between HDR and non HDR channels.

As for dimming mode well it can be made by playing with R G B values of the color palette. If you have a algorithm for that its not difficult to implement. But i doubt a developers will start to think for algorithm on their own.

If you propose an algorithm then there is a chance to be implemented....