AFAIK it only happens when transcoding to H264. It’s most noticeable on anime for me because that’s typically the only thing that ever needs transcoding on my setup when it needs to burn subtitles, and I have HEVC disabled because it doesn’t play nice with Kindle Fire tablets.
I transcoded to H,264. Again, could no repro from this sample.
PS: I will move the bulk of this group of threads to the Discussion thread later today.
When we find a producible issue for Chris, we’ll post it here.
Like @Atomatth said here, you should get in contact with @chrisallen. He managed to reproduce and somewhat categorize the issue back in 2023.
@chris_decker08 saw some other subtitles mentioned here so I thought I would mention. DVB_Teletext subtitles on Australian Live TV completely crashes the whole server when enabled. Unsure if this is player related, transcoder related or both.
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@tree2369 can you easily reproduce? If so, can you please enable debug logging, reproduce the issue, then grab your PMS logs and share them here?
Also, can you confirm that this is only happening on the Forum Preview build and not the current production/beta channels?
4 posts were merged into an existing topic: Transcoder Upgrade Preview - Discussion
@Atomatth Can definitely get some logs.
Though yes this is also a issue that affected the production/beta channels, though only very recently.
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@chris_decker08 I’m seeing some issues with media that is UHD DoVI Profile 8 with HDR10 fallback and transcoding down to 720p for remote viewing.
Colors are acting weird, almost like it’s not falling back to HDR10 when transcoding. Occurs on iOS and tvOS with both the New and Old Experience apps. I’m getting bursts of green and magenta randomly.
Swapping out the Transcoder Preview for server Version 1.41.8.9834 corrects the issue. Logs attached.
Plex Media Server Logs_2025-07-12_16-57-51.zip (5.2 MB)
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This is great news, and I’ll give it a whirl after I return from a business trip. Right now, I’m “downloading” movies to be able to watch them on the plane, and I am using the new Plex app on iOS 18.5. The server is only transcoding one movie at a time, and only using a single thread/core. I have “maximum simultaneous video transcodes” set to 4.
If I were playing the same titles on my Apple TV or iPhone with transcoding, the CPU / GPU usage would be a lot higher. I expected that the download function would use the same transcoding functions as live playback and be much more performant. Plex is running on a Mac mini M1 with 16 GB of RAM.
Is this a known issue specific to Downloads? Will this new ffmpeg library improve this behavior, or is that a separate issue?
@djfriday13 I am classifying this under the category of follow on work as the upgrade is a pre-perquisite but requires additional work on both PMS and the client.
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@tree2369 like @Atomatth said, logs will defiantly be helpful here. Its possible that my work on A53 CC subtitles will fix this for you, however since I cannot repo we won’t know until you try 
@dklein is this only for dovi profile 8 or all HDR10 content? can you provide a sample?
@theirongiant there are some new settings in 1.42.0 which will help with this! This should be released to the beta channel as soon as later today.
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Awesome to hear, Chris!! Any chance your next build will be rebased (or whatever the technical term is) to pull these settings in / make them available, as well?
I haven’t decided yet, but the next build will be at a minimum based on the public build. I will make the decision at the time on whether or not it will be based on the beta build depending on known issues/how long the build has been in beta in order to maximize stability.
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Hi Chris,
I’ll PM you a sample shortly. When playing back this content, it looks flat (ie LOG) instead of HDR/DoVI. Primarily seems to affect the legacy players, as I don’t see the same issue on the tvOS New Experience Beta or on my iOS device running 2025.21. However, I do see the issue on tvOS and iOS running 8.45 with the Transcoder Preview server version. Swaping over to the current non-transcoder preview beta of the server corrects the issue in all clients.
@dklein are these files profile 8 or profile 8.1?
Hi Chris,
Both my test files are profile 8.1:
Video
ID : 1
Format : HEVC
Format/Info : High Efficiency Video Coding
Format profile : Main 10@L5@High
HDR format : Dolby Vision, Version 1.0, Profile 8.1, dvhe.08.06, BL+RPU, no metadata compression, HDR10 compatible / SMPTE ST 2094 App 4, Version HDR10+ Profile B, HDR10+ Profile B compatible
Codec ID : V_MPEGH/ISO/HEVC
Duration : 29 min 27 s
Bit rate : 24.1 Mb/s
Width : 3 840 pixels
Height : 1 606 pixels
Display aspect ratio : 2.39:1
Frame rate mode : Constant
Frame rate : 23.976 (24000/1001) FPS
Color space : YUV
Chroma subsampling : 4:2:0 (Type 2)
Bit depth : 10 bits
Bits/(Pixel*Frame) : 0.163
Stream size : 4.95 GiB (97%)
Language : English
Default : Yes
Forced : No
Color range : Limited
Color primaries : BT.2020
Transfer characteristics : PQ
Matrix coefficients : BT.2020 non-constant
Mastering display color primaries : Display P3
Mastering display luminance : min: 0.0050 cd/m2, max: 1000 cd/m2
Maximum Content Light Level : 275 cd/m2
Maximum Frame-Average Light Level : 57 cd/m2
Video
ID : 1
Format : HEVC
Format/Info : High Efficiency Video Coding
Format profile : Main 10@L5@Main
HDR format : Dolby Vision, Version 1.0, Profile 8.1, dvhe.08.06, BL+RPU, no metadata compression, HDR10 compatible / SMPTE ST 2094 App 4, Version HDR10+ Profile B, HDR10+ Profile B compatible
Codec ID : V_MPEGH/ISO/HEVC
Duration : 6 min 0 s
Bit rate : 5 875 kb/s
Width : 3 840 pixels
Height : 2 160 pixels
Display aspect ratio : 16:9
Frame rate mode : Constant
Frame rate : 23.976 (24000/1001) FPS
Color space : YUV
Chroma subsampling : 4:2:0 (Type 2)
Bit depth : 10 bits
Bits/(Pixel*Frame) : 0.030
Stream size : 252 MiB (88%)
Language : English
Default : Yes
Forced : No
Color range : Limited
Color primaries : BT.2020
Transfer characteristics : PQ
Matrix coefficients : BT.2020 non-constant
Mastering display color primaries : Display P3
Mastering display luminance : min: 0.0001 cd/m2, max: 1000 cd/m2
Maximum Content Light Level : 883 cd/m2
Maximum Frame-Average Light Level : 349 cd/m2
Also looks like you’re not accepting PM’s right now
I’m curious about this question. There’s no “plain” profile 8, the base/compat is always either HDR10 (8.1) or HLG (8.4). I’m just curious, wondering if I’ve missed something in the DV world.
