Server Version#:Synology Server Version 1.32.8.7639
Player Version#:Plex Web Version 4.119.2 && iOS Version 8.28
When I perform hardware transcoding streaming media playback on the plex web web page, when playing a movie with PSG format subtitles, I found that the CPU usage reached nearly 100%. I used intel_gpu_top to check and found that the Render/ 3D occupancy is 0, and only the Video and VideoEnhance modules are called to a small extent, but they are much smaller than the values during normal hardware transcoding. The GPU is the Integrated GPU of the Intel N5105 processor. I searched on the Internet and found a post that also stated that plex does not support the transcoding of some subtitles (pgs, ass, etc.). After the suggestions given in those posts, I found that when I select the fixed subtitle option to “Image format only” on the mobile iOS client, the client can trigger relatively normal nuclear display hardware decoding (even so, the plex transcoder process The CPU usage is still as high as 40%-50%, and the movie is 4K HDR HEVC encoded with a bit rate of 25Mbps), but on the web side, no matter how I adjust the subtitle options, the graphics card always does not work normally, just as mentioned above. It seems that the CPU is completely soft decoding . For other subtitle formats or files without subtitles, hardware transcoding can work normally. I saw some videos on the Internet testing hardware decoding, and found that jellyfin, an open source software, can use the N5105 processor to smoothly transcode on Synology. The bit rate is higher than the movie files with the same encoding and subtitle format that I tested the movie, and the transcoding The CPU usage of the process ffmpeg is only 10%-20%.
Can plex be optimized for this issue and solve this bug?
Feedback on the problem that PGS format subtitles do not work properly during hardware transcoding o
We are aware of the PGS, VOBSUB, and DVDRIP subtitle burning problem.
There was a staffing change.
With our new team, we’re fixing these long standing problems as quickly as we can.
Hardware subtitle transcoding is either the next or second thing for us to do (there was quite a list but we are getting there)
Hey Chuck, wanted to check in on this to see if there has been any movement.
I just got an Arc GPU (I know it’s not supported) and transcoding is great but the single thread performance of PGS transcoding is still killing my server. It’s a limited case issue (only 1 of my family members has some hearing impairment) but it’s still a real quality of life issue.
I’ve bought a shield for myself but my family members aren’t as willing to drop that much money on a client device.
There is movement… quite a bit to be precise.
Nothing will happen until after all are back.
It looks really good. Lots in the works but not for me to disclose.
There will be final testing for us to do as well before we unveil.
Not to become “that guy” but wanted to check in on the status of this fix.
If you don’t want to be “that guy” – then don’t be! 
Technically…
They’ve always worked as they currently do.
Is it ideal? No.
Current status is:
-
We are working on the new development pieces for subtitles.
(converting text → image and then burning in HW) -
PGS, VOBSUB, and DVDRIP are the easy part.
The more important info here is the updating of the Transcoder itself and fixing the bugs which we discovered during our full regression testing suite.
The transcoder’s not been updated in quite some time so it’s important to get it updated as we move forward with the new work. While we’re doing this, we’re also correcting the known issues we have with it.
I will report when I can report. For now, all I can ask is hanging in.
I’m glad to see someone following up on this feedback. After using it for the past two months, I want to add some more content about the subtitle transcoding issue.
The picture shows the working status of the graphics card that I checked with the intel_gpu_top tool. I’m not a technical person, so I don’t understand very well what these four items do in the actual transcoding process. But under normal circumstances, when hardware decoding works normally (CPU runs at low level), the first item Render/3D and the third item Video are working.
My previous feedback was limited to psg subtitles, but I found that it seems that in some specific situations, the hardware decoding of SRT or ASS subtitles is also not working properly, which usually occurs in specific client/web scenarios.
Hardware decoding does not work means: the server shows hardware decoding, but plex transcoder still occupies a high CPU, the render/3D module in the above intel_gpu_top tool does not work, and only the Video module is working.
The problem I found recently about SRT subtitles is on the Android 6.4.1 client (because the TV box only has Android 4.4.4 version, this is the highest client version I can install and can display the poster normally), the server has been updated to the latest beta version 1.40, when loading high-bitrate videos that require srt subtitles on the TV, the above “hardware decoding does not work” situation occurs. I wonder if it can be alleviated by supporting srt or ass subtitles burning and solving the hardware decoding problem of burning. I want to know if this problem can be solved only by updating the server transcoder or if it is a problem that also occurs on old client versions and cannot be resolved without updating the client.
Another thing is that when I trigger transcoding on the TV due to the source video (4K H264->1080P H264) resolution exceeding the limit (mounting srt subtitles), the CPU occupancy caused by the above is only 25%, and there are a lot of CPU resources in idle state. I set the working mode of the transcoder on the server to automatic. In this case, even if it is software decoding, considering that the CPU is not fully loaded and the source video is H264 encoded, I think it should be able to play smoothly. Is it not aggressive enough in scheduling the CPU to ensure smooth playback?
I got a load of movies & tv shows that have PSG subs, Too many to find & convert to SRT, So this news sounds wonderful to me. Im may also be downgrading my Plex server from a gaming PC in awhile (i5 13th, 16GB, RTX 4060), to a much lower power Beelink s12 Pro (Intel 12th gen Alder Lake N100, 16GB, Intel UHD Graphics), So converting in HW on a little box like this would help a lot.
Great news 
EDIT: If I’m reading your post right, The CPU would still be used to convert the PSG sub text to image, But instead of using the CPU to burn/trancode it in to the video, HW will be used to do the rest of the heavy lifting burning in/Transcoding? Thanks again 
Not quite correct.
- Video image transcode will continue to be done in hardware
- PGS, VOBSUB, or DVDRIP (image based subtitles) will be overlayed into the video image WITH HARDWARE.
- The CPUs only task is to coordinate when to and when not to inject the subtitle frame (a picture) into the image stream. The hardware will now do the actual merging.
I follow the topic of PGS and 4K HDR and transcoding on here from time to time. It has bedeviled me for years. I have a Linux box, speedy AMD processor, and high end QUADRO card. It is my policy now to convert all subs to ASS for 4K HDR titles… else, Plex is not usable. (SRT works too, but not near as pretty or customizable as ASS.) This is kind of labor intensive but I have grown to like ASS and its flexibilities. Only with ASS will the transcoder stay “above 1.0”… with PGS, the transcoder dips below 1.0 every half minute or so, the video pauses/stutters a few seconds, but resumes. My CPU utilization hits about 25% with ASS, but 50-75% with PGS.
Plex has made me something I never thought I’d want to be: an ASS man.
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