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So I understand that Plex HW transcoding is not related to ability to burn PGS/VOBSUB.
It will required pure CPU power to burn image subtitles onto transcoded media.
The question is what’s the recommanded CPU/Passmark for this task?
Is the Intel NUC with Intel Core i3-8109U (Passmark 6184) will be able to do it smoothly ?
Let’s say the MKV 1080p with PGS subtitles.
It depends also on the used video codec and the bitrate of you video files.
This CPU has a relatively high “single-thread rating”, which is good for this type of task.
It could work with Bluray remuxes which use H.264 and a bitrate of up to ~35 mbps.
Maybe even with VC-1 (although it is advisable to pre-transcode these to H.264 before putting them into Plex.)
If your files use HEVC (H.265) it will probably not work - unless you also activate hardware transcoding.
OK. Thanks for the answer.
One more thing, it’s very strange that if I turned off the HW transcoding.
I’ll be able to watch these movies (MKV + PGS, 1080P) without any buffering. … at CPU 100%.
But once I turn HW transcoding on, the movie will started to buffering every 10 seconds. … at CPU 25-30%.
If my CPU (J3455) can do software transcoding, why can’t they also do with HW transcoding ?
Good question!
Please share the contents of the Plex XML info of this movie.
839.rar (7.1 KB)
here you are
I can’t see any apparent obstacles in the XML which could cause this issue.
The burning-in of subtitles can only use a single CPU core and can also not use the hardware accelerator.
https://www.cpubenchmark.net/cpu.php?cpu=Intel+Celeron+J3455+%40+1.50GHz
There might be other constraints in this extremely weak cpu which only manifest themselves when trying to use hardware transcoding in conjunction with subtitle burning.
I can’t say for sure though.
Which Plex client is used? Is the behaviour identical, no matter which client type is used?
They are difference, as following
Chrome (1080P): Buffering every minute or two (Dell XPS15 ,i7-6700HQ)
iPad 3rd Gen (Direct Play) : Video and Audio out of sync // some other time it’s all good … not sure why
iPad 3rd Gen (720P) : Buffering every 5 minutes
Samsung 4K TV (1080P): Buffereing every minute
Samsung Galaxy S8 (Direct Play) : All good
How do you get the iPad to direct play?
Are you running a beta version of the iOS Plex app?
I recommend you to use PMP on a PC or Mac, instead of the web app in Chrome. It can direct play all kinds of subtitles.
I assume that playback is fluid, as soon as you disable all subtitles, right?
For iPad, I download Plex App from App Store. Nothing special. It says version 5.8.
Without PGS/VOBSUB or with SRT sub. Playback never has any issue. Even 4K H.265 is silky smooth.
Trying the Plex Media Player for Windows now… let’s see
Update : Plex Media Player resolve the buffering issue on PC because it’s Direct Play.
But there still no answer to why SW transcoding is working better than HW transcoding while using the same CPU. If overlay task of image subtitle is limited to one CPU, why the SW transcoding is not struggle at all ?
Sorry, I don’t know. I can only take a guess, like above
There might be other constraints in this extremely weak cpu which only manifest themselves when trying to use hardware transcoding in conjunction with subtitle burning.
If you have the chance to test this with a different (stronger) cpu, like the one you mentioned in your first post above, I’d be very interested in the outcome.
I tried install PMS to my Dell XPS15 and transcoding the same file.
The Intel Core i7-6700HQ (Passmark 8133) can handle the transcoding quite OK. Got the speed around 1.X - 2.X in verbose log. No buffering with CPU around 10-25%.
I also add more challenge by play 2 movie at the same time (both with PGS/VOBSUB and HW Transcoding) also no buffering with CPU around 50%
Finally, added another movie and play 3 of them simultaneously. Same PGS/VOBSUB transcoding. CPU peak at 100% and the 3rd client is buffering every few minutes.
So my guess is Intel NUC with Intel Core i3-8109U (Passmark 6184) ~ 75% of 6700HQ CPU score might barely make it for a single 1080P and PGS/VOBSUB transcoding. I’m not sure if the transcoding speed and Passmark score relation is linear or not. If any Plex Staff can provide the answer it would be appreciated.
Conclusion : If money is not an issue, one should better get the bigger NUC model with Intel Core i5-8259U ( Passmark 10954) for PGS/VOBSUB transcoding.
You might be right. After all the Core i5-8259U has double # of cores and also a higher clock rate.
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