Today I thought I would start to experiment with subtitles using PMS.
Sooo.
I ripped a couple Blu-Ray disks with both external subtitle files and re-muxed subtitles.
With re-Muxed subtitles, they show on the Plex Clients selection but do not show on the movie display, Transcoding goes thru the roof but still no subtitles.
With external subtitles, The subtitles do display.
Why is that??
The BIG problem is, in either case, when subtitles are used transcoding consumes 80% of CPU resources and I gat an error on screen from the client that says my processor or bandwidth is not hi enough for the media to play.
The movie does play but sucks up enormous CPS cycles.
I run an i7 with and SSD for temp transcoding…
I normally can run about 5-7 concurrent transcodes that consume 90% CPU, without subtitles.
With subtitles only one stream cam be rendered using subtitles at 80% CPU load.
This makes, for me, implementing subtitles VERY restrictive.
short version: get SRT subtitles and tell Plex Web to render them directly, instead of asking the transcoder to “burn them in”.
Choose your Plex clients carefully if they are able at all to display subtitles.
Many can only do text-based (SRT, TX3G) ones.
Very few are able to handle bitmap-based (PGS, VOBSUB).
That article you sent me the link to is irrelevant to my question.
Why do subtitle transcoding bring my server to its knees when normally I can run 5-7 transcodes concurrently?:?
This is happening to me on every Plex Client I use… PlexWeb, Roku, IOS, PS4, Xbox
In fact on the Roku 4 It causes 100% peak CPU usage then randomly stops displaying subtitles all together!!!
Not only brings my server to it’s knees, on plex web it complains I do not have enough processor power (i7 / w 256gig SSD) or bandwidth (300meg down / 20meg up)
I feel it is very relevant to your problem: displaying subtitles.
I can only assume that “burning in” subtitles is poorly optimized or not ‘multi-threaded’ in ffmpeg (from which the Plex trancoder is derived).
So performance suffers greatly if the transcoder must not only transcode video but also superimpose the subtitle text on top of it.
Well yes but when no subtitles are in use… The video direct plays at 2% CPU Usage, making this not an additive thing… IE. Transcoding then adding text over the image…
I have tried both burned in subtitles and external. Both methods exhibit the same problem… (Except Burned In Subtitles do not display in burned in mode)
I edited my post above with a little more info as well.
Could it be that my subtitle rips are IDX/SUB format not SRT???
Plex does recognize the external IDX/SUB files
One thing Plex seems to do with the IDX/SUB files is… in the subtitle dropdown on Plex Web there are 2 instances of each subtitle language both indicating type IDX
@jjrjr1 said:
I read the article that VOBSUB will always transcode.
Is that the difference between IDX/SUB and SRT??
Whether it transcodes depends entirely on which type of client is used.
But only PMP and OpenPHT can display bitmap-subtitles.
(Actuall the Shield can do it too, but only if the file is Direct-Played)
Can IDX/SUB be converted to SRT and will SRT subtitle files stop this behavior??
Yes, by a process called Optical Character Recognition (OCR). It is prone to errors, so manual correction and review is almost always necessary.
If you have a Windows computer, you can give it a try with Subtitle Edit
Why does transcoding with subtitles use soooo much more CPU than just normal transcoding??
I already attempted to explain that above.
Cripes I am running an i7 and it cannot keep up with just one movie using subtitles??
i7 is not i7. What exact type do you use?
Look it up here http://www.cpubenchmark.net
look in particular at the “single-thread rating”
Plex has always handled .srt (internal and external) subtitles better in my experience. You will see no transcoding with SRT
I’m not technical minded enough to know why that so sadly have no answer for you. Some clients handle non SRT better than others.
Do you need subtitles all the time or is it just for English movies with foreign parts audio?
So how powerful of a box do I need for Plex to be able to play just 1 movie transcoding with subtitles?? (Without subtitles I can transcode 5 concurrently)
The passmark of my CPU is around 9000.
So you are saying this is expected behavior for Plex using subtitles???
Geeess…
Useless
So how powerful of a box do I need for Plex to be able to play just 1 movie transcoding??
The passmark of my CPU is around 9000.
So you are saying this is expected behavior for Plex using subtitles???
Geeess…
Useless
Honestly I have an i7 (passmark around 1000) that I share I hit 4 simultaneous 1080p transcodes without issue. If the VOBSUB causes more stress than a simple video transcode I don’t know… But I’m sure Otto will.
@jjrjr1 said:
So how powerful of a box do I need for Plex to be able to play just 1 movie transcoding??
The passmark of my CPU is around 9000.
The overall passmark score only tells one half of the story. Please see above. You need the “single-thread rating” too.
I am using an i7-4770 CPU @3.4GHz in my server.
It has a passmark score of 9811 points and a ‘single thread rating’ of 2229
With this, when I watch one movie with PGS subtitles in 1080p in Plex web, overall cpu load stays under 50%.
This is only valid for a movie file which is encoded with H.264.
If I use a VC-1 video with ~14mbps, I get juddering.
If I use a H.265 video I get serious buffering.
@jjrjr1 said:
Yup without subtitles I get about the same performance…
LOL
Otto is to smart for me.
I cannot understand most of the tech stuff.
None of this behavior with subtitles make any sense to me…
LOL
By same performance without subs you mean same as me? Or just still the same 1 transcode hammering the server to death? If you mean the former then yeah obviously there is something excessive with VOBSUB beyond a normal transcode.
Again its not much help to you but as mentioned some clients cope better than others with non SRT. I was a long time user of Orca’s Samsung app. If I recall one of his updates allowed for direct play or many more formats than SRT. Sadly I upgraded my TV to one that cannot run Orca’s app so I cant even test it.
Totally the same with the tech stuff… Much of it is beyond me…(key mapping springs to mind)
Anyway Hopefully @OttoKerner can confirm if certain sub transcoding is more stressful than a video transcode.
Hope you get it sorted.
@HitsVille said:
Anyway Hopefully @OttoKerner can confirm if certain sub transcoding is more stressful than a video transcode.
Yes, it is more stressful.
Additionally to decoding and encoding a video, it also has to superimpose a text on top of the video.
Due to technical reasons in the Plex trancoder this process sometimes cannot use all cores in a cpu.
The best solution is to use SRT subtitles.
The second-best solution is to make the user comfortable with using either PMP or OpenPHT.
@HitsVille
Yup without transcodes. I can stream 5-7 transcodes (1080p) concurrently.
Certainly does mean subtitles need a ridiculous amount of CPU to perform the transcode needed. (Not Ready for Practical Use)
And if I have to go thru gyrations to make an SRT file from my DVD/Blu-Ray Rips, It will never happen.
Thanks @OttoKerner
As suspected. Plex with subtitles not quite ready for prime time.
Use OpenPHT or PMP on a Roku4?? How??
@HitsVille said:
Anyway Hopefully @OttoKerner can confirm if certain sub transcoding is more stressful than a video transcode.
Yes, it is more stressful.
Additionally to decoding and encoding a video, it also has to superimpose a text on top of the video.
Due to technical reasons in the Plex trancoder this process sometimes cannot use all cores in a cpu.
The best solution is to use SRT subtitles.
The second-best solution is to make the user comfortable with using either PMP or OpenPHT.
Yeah personally I’m on PMP only use SRT and only need for foreign audio parts.
And yeah sorry I must have totally missed your earlier post about the single thread rating… Apologies for making you repeat yourself .
Anyway at least @jjrjr1 is aware of his options. Thanks Otto
@jjrjr1 said: @HitsVille
Yup without transcodes. I can stream 5-7 transcodes (1080p) concurrently.
Certainly does mean subtitles need a ridiculous amount of CPU to perform the transcode needed. (Not Ready for Practical Use)
And if I have to go thru gyrations to make an SRT file from my DVD/Blu-Ray Rips, It will never happen.
Thanks @OttoKerner
As suspected. Plex with subtitles not quite ready for prime time.
Use OpenPHT or PMP on a Roku4?? How??
Yeah think Otto meant as an alternative…
You could have a look at subscene opensubtitles etc, for you subs but certainly not ideal if its a massive amount of movies.
