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User profile for user: Olivier VM
Olivier VM Author
User level: Level 1
19 points

Black levels / contrast change with subtitles

Hello everybody,

since the last updates of iTunes (11.1.5) + OS X (10.9.2), watching a movie with subtitles is no more comfortable. I see that other people on the forum also encountered the problem.


I'll try to be clear and detailed:

Each time a subtitle is displayed, the black level (or the contrast if you prefer) on the full screen slightly becomes brighter. The result is a flashing movie each time someone is speaking (subtitles). This was not present before the very last updates. This is especially very annoying when watching a movie with top/down black bars (cinema 2:1 image ratio), as there is a big area of black pixels. Or watching a story in space (try Gravity...). I would say: it is not watchable...


This happens (in my case) when using full screen mode, HD movie, and HDTV connected via HDMI. Maybe in other situation also, I don't know.


But for instance, wathching the HD version using a window (not clicking on fullscreen double arrow) on the TV, or SD version in full screen on an external monitor (which is not HDCP compatible), or SD version of the movie in full screen to the TV via HDMI, the issue is not visible. In fact the problem is not present in these situations because the contrast levels on the full screen remains brighter always, even when there is no subtitle. So there is no flashing behaviour. But the black is "not black" anymore. It is dark grey.


Do you know whether this is already reported to Apple dev team? Is it a known issue?

Should I report?


Thanks.

Mac mini (Late 2012), OS X Mavericks (10.9.2)

Posted on Mar 24, 2014 2:24 AM

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User profile for user: gagarski
gagarski
User level: Level 1
13 points

Posted on Mar 11, 2018 4:33 PM

Okay, I'am suffering from this problem for about two or three weeks on my MacBook Air Late 2014 (MD761RU/B). But for me it happens only in Chrome. It does not happen in Firefox, Safari or even other Chromium-based browsers (like Yandex). I even ended up reinstalling macOS but it didn't help.


I could not get consistent brightness changes on Netflix but today I found a video on Amazon Prime Video where I can clearly and often see this flickering that causing me eye-cancer. By evening I nearly memorised these 2 minutes of video by heart.


After reading halo_bone's post I've tried to play with some settings (contrast especially) in System Preferences / Accessibility / Display section.


First of all, increasing contrast here makes these bursts more noticeable and now you can definitely see them (TBH, I initially thought that it was some kind of optical illusion).


Then I enabled inverted colors and now I could clearly see what @halo_bone says: macOS treats screen differently when there is full screen video without subtitles and when there are subtitles. Here is how I could see it. Most movies have wider aspect-ratio than MacBook display so I had black stripes on the top and on the bottom of the screen. The thing is they were black when there is no subtitles (so these parts of screen are not inverted) and white where there are subtitles. Now I can clearly see that it DOES happen in Chrome and DOES NOT happen in Safari or Firefox (they always have white stripes).


The last part is most mysterious. Previous steps helped me to see the problem more clearly but did not fix it. Then I accidentally (or just for fun) increased the cursor size (WHAAAT?) with slider and then turned it back to its normal size. You won't believe it but after that this annoying flickering just disappeared! I can clearly see in inverted colors mode that flickering is no longer happening. After rebooting the computer it starts to happen again, but it works fine after closing and opening the laptop lit. Turns out that changing cursor size somehow disables special treatment for full-screen video (top and bottom stripes becomes always white).

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User profile for user: Nathan Alderman
Nathan Alderman
User level: Level 1
14 points

Oct 17, 2014 6:23 AM in response to radio662

I'm now beginning to suspect an error with the Intel HD4000 graphics chip in my late 2012 Mac mini. As noted in hartze11's post above, it's had problems with handling HDMI and HDCP in the past. And the problem doesn't just lie with iTunes; I also get an HDCP error when trying to stream Flixster movies in high-def, even though the conditions that should trigger that error -- a dual-monitor setup or a DVI connection -- aren't present. I've also noticed a less severe version of the problem in iTunes when using a miniDisplayPort-to-HDMI adapter to connect my MacBook, which also has Intel HD4000 graphics, to an external HDMI monitor.


Other video sources -- Netflix and Hulu Plus via Safari, video from my EyeTV -- play just fine, with consistent black levels.


I have a Toshiba 46xv545u from 2009 and an HDMI 1.3-compliant cable. The TV's set to PC input. In System Preferences > Displays, Overscan is off. I've tried turning on the TV first, then the Mac mini, to achieve a proper "handshake." I've also tried turning the TV off, leaving the Mac mini on, and then unplugging and replugging the cable from the mini. Nothing thus far has worked.


This is incredibly aggravating, and I really hope there's a fix for it. I never had this kind of problem with my previous, 2006- or 2007-era Mac mini, which connected to my TV via a DVI-to-HDMI cable. I, too, would love to know how to best report this issue to Apple.

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User profile for user: aycwong2
aycwong2
User level: Level 1
0 points

Oct 21, 2014 9:28 PM in response to poitvd

Yes.. out of all the "fix".. this is the only one that works..


I've tried re-adjusting my screen gamma setting and all that..


but it looks like "English CC" as a subtitle OR no subtitle are the only ones that won't cause the flicker when you go into full-screen mode. I've tried all the other subtitle choices and they all go nutty.


I guess spending 2 nights playing around with this is enough time wasted until they come up with permanent fix.


Now if I can get continuity working on my Mac and iPhone 5.. sigh..

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User profile for user: njdoyle
njdoyle
User level: Level 1
10 points

Nov 1, 2014 11:20 AM in response to Olivier VM

I've found a workaround!


It seems that this started going wrong when Apple started outputting YCbCr over HDMI instead of RGB. Here's a link that describes how to force OS X to send RGB signal to your display which seems to solve the problem.


I used the patch-edid.rb script found here: http://embdev.net/topic/284710#3027030

It makes some files that you just need to put in /System/Library/Displays/Overrides/. Reboot.


After the reboot, your display will probably be dark universally, not just for full screen videos. Use the color calibration options in System Preferences -> Displays -> Color to calibrate your display back to normal. Full screen videos in iTunes and elsewhere should now stop 'darkening' on full screen.

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User profile for user: Nathan Alderman
Nathan Alderman
User level: Level 1
14 points

Nov 2, 2014 4:35 PM in response to njdoyle

I ran the script, but while it seemed to run correctly, I didn't see any new files created. Is this something that'll appear on the desktop via the Mac's GUI, or will I have to use Terminal commands to copy them to the proper directory? (I know just enough about Terminal to be dangerous. How to copy files is, alas, not within the scope of my knowledge.)


A step-by-step walkthrough for those of us sadly lacking command line skills would be most appreciated. And thanks much for finding this!

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User profile for user: mjs1234
mjs1234
User level: Level 1
8 points

Nov 13, 2014 8:13 AM in response to Nathan Alderman

Has anyone tried this?


Mac mini EFI Firmware Update 1.7


I too am disappointed that when I tried to watch an HD movie, if it had subtitles, the screen's black level/contrast changed every time a subtitle came on and off.


Also, anyone tried a thunderbolt to HDMI cable to see if that would help?


I'm going to try both of the above solutions and I'll get back to you if I have any success.

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User profile for user: ScutterOz
ScutterOz
User level: Level 1
0 points

Dec 11, 2014 10:11 PM in response to mjs1234

+1 from me too.


Same setup, Macmini6,2 with no display just a direct HDMI connection from MacMini to an external HDTV.


I must say i first only noticed the contrast change when the onscreen controls vanishes. As soon as they disappear the display goes darker making dark scenes loose so much detail and hard to see. However, i can confirm i also have the issue of the contrast flicking between light and dark when subtitles are turned on too.


One thing i have noticed though. I have content sourced from various sources shall we say, and it only seems to do this on movies and TV shows purchased from itunes. Full HD bluray rips i also have don't have the same problem. I'm not familiar with the technicalities of the media formats but it seems to be more down to the encoding than the hardware.... but like i say i'm no expert on the matter just putting the info on the table as i see it.


The mac is currently on Mavericks, but had the same issue with Yosemite before i uninstalled it (i won't go there). I didn't have this problem prior to iTunes 12, or at least i never noticed it.


mjs1234, an interesting idea about the thunderbolt to HDMI - i'll give that a whirl over the weekend and see if it makes a difference.


BTW the only worthwhile solution i have had so far has been to use my appleTV to watch movies i've purchased from iTunes. Streaming them directly from itunes on the MacMini... not ideal and defeats the purpose of having the mac connected to the TV, but it does work and its not a major PITA either. If it is a real nightmare getting this working for you it might be worth the purchase of an ATV.

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User profile for user: dropbars
dropbars
User level: Level 1
0 points

Jan 13, 2015 8:41 PM in response to Olivier VM

HEY!!!!!!!!!! MAC TECH GUYS!!!!!!!!

Answer this posting please.

Wether it's the player overlay or subtitles the problem happens when they disappear from the screen the image gets noticeably darker, if it's a scene that already dark you can't see much at all.


The only work around I have found is to put the player overlay in the corner with the mouse icon hovering over it, but this is still noticeable while watching the movie and becomes very distracting.


2012 Mac Mini

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User profile for user: Kasper_dk
Kasper_dk
User level: Level 1
0 points

Jan 22, 2015 5:23 AM in response to Olivier VM

Macbook Pro Retina 15", Yosemite. Fully updated.

Same thing... Actually started for me on my old computer running Mavericks. Started using VLC as default player for everything as I couldn't find any workaround - or even discussions about it a the time.

Last night I rented a movie through iTunes (having happily forgotten about the issue) and it's still doesn't work:

- Gamma changes with subtitles visible

- Gamma changes when player controls visible

- Highlights are broken and full of purple noise

- and there's absolutely nothing I can do about it.....

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Black levels / contrast change with subtitles

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