Display issue with 4K SDR videos and iPad Pro with Mini LED

Sprites · September 4, 2023, 2:45pm

Infuse (7.5.9) with a Plex server.
iPad Pro M2 12.9 Mini LED display (iPadOS 16.6).

For context, a nice characteristic of the Mini LED display on the iPad Pro 12.9 is how the areas that are pure black (like the top and bottom black bars of a movie, for example) are completely pitch black because the LED screen won’t be lighted up at all in those areas.

And it generally works great when using Infuse… Except when playing 4K SDR videos.

For some reason, the combination of this specific resolution with this specific color space makes the Mini LED screen to completely light up, like if the dimming zones weren’t working. Basically, when playing 4K SDR videos in Infuse the Mini LED acts like a regular LED display would.

And it’s only with 4K SDR videos. 4K HDR and regular 1080p (SDR) work perfectly, the top and bottom bars are pitch black. But with 4K SDR they’re gray (because the whole LED screen is lighted up).
I also tried playing the same 4K SDR videos in the Plex player app and also in their web app (using Safari), and the Mini LED display is behaving correctly, so it seems to be an issue specific to Infuse.

It’s not particularly noticeable in a well-lit room but in a dark room it can be seen right away, that’s how I first noticed the issue (I love watching movies on my iPad in bed at night)

Is it possible that for 4K SDR files there’s some kind of problem in the way Infuse communicates with some APIs?

Please let me know if I can help in any way to troubleshoot and fix the issue.

munpip214 · September 4, 2023, 3:10pm

Can you post a MediaInfo (on App Store or MediaInfo) details of a 4K SDR video?

Sprites · September 4, 2023, 4:17pm

Sure. Here it is:

General
Format                                   : Matroska
Format version                           : Version 4
File size                                : 36.5 GiB
Duration                                 : 1 h 57 min
Overall bit rate mode                    : Variable
Overall bit rate                         : 44.6 Mb/s
Frame rate                               : 24.000 FPS

Video
ID                                       : 1
Format                                   : HEVC
Format/Info                              : High Efficiency Video Coding
Format profile                           : Main 10@L5.1@High
Codec ID                                 : V_MPEGH/ISO/HEVC
Duration                                 : 1 h 57 min
Bit rate                                 : 41.5 Mb/s
Width                                    : 3 840 pixels
Height                                   : 2 160 pixels
Display aspect ratio                     : 16:9
Frame rate mode                          : Constant
Frame rate                               : 24.000 FPS
Color space                              : YUV
Chroma subsampling                       : 4:2:0
Bit depth                                : 10 bits
Bits/(Pixel*Frame)                       : 0.208
Default                                  : Yes
Forced                                   : No
Color range                              : Limited
Color primaries                          : BT.709
Transfer characteristics                 : BT.709
Matrix coefficients                      : BT.709

Audio #1
ID                                       : 2
Format                                   : DTS XLL
Format/Info                              : Digital Theater Systems
Commercial name                          : DTS-HD Master Audio
Codec ID                                 : A_DTS
Duration                                 : 1 h 57 min
Bit rate mode                            : Variable
Bit rate                                 : 1 769 kb/s
Channel(s)                               : 6 channels
Channel layout                           : C L R Ls Rs LFE
Sampling rate                            : 48.0 kHz
Frame rate                               : 93.750 FPS (512 SPF)
Bit depth                                : 16 bits
Compression mode                         : Lossless
Title                                    : DTS-HD MA 5.1
Language                                 : English
Default                                  : Yes
Forced                                   : No

Audio #2
ID                                       : 3
Format                                   : AC-3
Format/Info                              : Audio Coding 3
Commercial name                          : Dolby Digital
Codec ID                                 : A_AC3
Duration                                 : 1 h 57 min
Bit rate mode                            : Constant
Bit rate                                 : 224 kb/s
Channel(s)                               : 2 channels
Channel layout                           : L R
Sampling rate                            : 48.0 kHz
Frame rate                               : 31.250 FPS (1536 SPF)
Compression mode                         : Lossy
Title                                    : Commentary Track
Language                                 : English
Service kind                             : Complete Main
Default                                  : No
Forced                                   : No

munpip214 · September 4, 2023, 4:23pm

Are all your 4K SDR movies 10 bit and 24.000fps? Those are two things that stand out to me. Also are the black bars integrated into the video file itself?

Sprites · September 4, 2023, 4:30pm

Some are 23.976 fps, but they are all 10 bit, yeah.

As for the black bars, I have a both cropped and uncropped files. They both have the same issue described in the first post. The MediaInfo output above is from an uncropped file.

Hmm… Yeah, it might be an issue with 4K SDR 10 bit files

Sprites · September 4, 2023, 5:05pm

So I made a quick and dirty 8 bit reencode of a few minutes of the above video, and can’t seem to reproduce the problem. The black bars are pitch black with this reencode.

Thanks @munpip214 for helping to identify the issue!

So right now it does seem the issue is with 4K SDR 10 bit videos.

munpip214 · September 4, 2023, 5:25pm

And maybe not all 10-bits are the same. Best for @james to take a look at one of the files. You can upload at Dropbox

Sprites · September 4, 2023, 5:27pm

Sure, if @james needs a sample I’ll happily provide one! Just let me know and I’ll make one from the same file listed in the MediaInfo output above.

But right now it does seem to happen with everything that is 4K SDR 10 bit.

Sprites · September 7, 2023, 8:04pm

If it can help, I could try on a Macbook Pro M2 16-inch with a Mini LED display.

I couldn’t reproduce the issue with any of my 4K SDR videos.

So the issue seems specific to the iPadOS app.

Sprites · September 27, 2023, 5:31pm

Any news about this issue?
Please let me know if I can help in any way.

james · September 27, 2023, 6:02pm

If you’re able to send in one of the problematic files we can take a look.

https://firecore.com/upload

Sprites · September 28, 2023, 2:00am

So I prepared a sample I was about to send, and when I tested it to make sure everything was alright I realized I wasn’t able to reproduce the issue at all.

Which is weird since all 10 bit 4K SDR videos definitely used to trigger the issue for me. But right now, nothing.

The only variables that changed since the last time I played such a video in Infuse are:

My iPad was updated to iPadOS 17.0.2
Infuse was updated to version 7.6.1

I suspect one of these two things fixed the problem…
Let’s be happy some issues are magically fixing themselves I guess?

I’ll mark the whole thing as fixed for now, let’s hope it stays fixed!