Server Version#: 1.27.1.5916 on Linux (Debian 11)
Player Version#: Plex for iPadOS v8.5, iPadOS 15.5
Starting relatively recently, HDR content played back from mkv files on my iPad 6 (model A1893) shows up as very washed out, to the point where there’s a visible difference between the letterboxing and the rest of the screen. Non-HDR content plays back just fine.
I have transcoding completely turned off on the server (since it’s low-powered and everything that I use Plex on is relatively capable and can use direct playback), so that shouldn’t have any effect. Other applications like VLC over SMB play back the same files without this problem, which I assume is something to do with the tone mapping on a non-HDR display like this one? I also have an iPhone XS with an HDR display and everything looks fine, but I don’t want to watch movies on it.
Here’s a couple of screenshots that show the problem, including one with the playback info overlay.
If your display has no support for HDR, and you also have disabled transcoding on the server, then what you see is exactly what is expected.
The Plex player cannot perform the “tone mapping” to convert the HDR data of the video stream into SDR for the screen on its own.
I don’t think that’s completely correct, for two reasons.
First, it used to work fine. I watched some of these same videos on this same iPad via Plex, from the same media server, and they didn’t have this problem. This was maybe two years ago? Something has changed in the iOS/iPadOS player since then, I think.
Second, other apps can do this without an issue. As I said in the original post, VLC for iOS is able to play these videos correctly on the same device through a Samba share. Tone mapping doesn’t inherently require transcoding, it just requires support in the player for conversion of the colorspace. mpv and the Plex desktop clients can both do this as well, so I’m surprised that the iOS/iPadOS client can’t.
If the Plex client for iOS/iPadOS can no longer do tone mapping while other applications on the same device can do so, then that’s an answer, I guess. For these files, I’ll just use the software that works but is less convenient.
Interestingly enough, for me, using the iPad app on my M1 MacBook Air plays HDR content washed out, but when using the web app, it plays great. Something going on between the Plex server and iPad app that is not right…
Since the thread is still open, I can definitely say that the problem is not the lack of transcoding support on the server. I’ve upgraded my Plex server to do hardware transcoding and the washed-out color problem still happens on the iPad when using the Plex app if Direct Stream is on. If I force the Plex app to ask the server to transcode the stream (by setting the home stream quality level to 1080p/10mbit or something along those lines) then it plays back correctly.
What’s also odd is that if I use the Plex web app in Safari on the iPad, and choose “Original” for the quality level, the colors are correct. It appears that the HEVC decoder in Safari is able to do on-the-fly tone mapping (from the HDR stream to the SDR display) in the same way VLC can, but the Plex app can’t unless the server transcodes the original stream to SDR.
Direct Playing my 4K UHD HDR remuxes on my new 10th gen iPad are completely washed out. Works perfectly fine on my iPhone 13 pro. Same maximum quality settings on both. Something is just wrong with the iPad app.
I have since upgraded to a 4th-gen iPad Pro with an HDR10/DV-compatible display, and Plex now plays back HDR content just fine on it. So for me, the problem is solved? This should probably still be addressed, though.
