Buffering issue on movies with subtitles in Synology DS218+

General Discussions
1

Hello,

I need some help, I have a Synology DS218+ using the latest Plex Pass version, direct play works perfectly (with hardware transcode), but when playing foreign language movies with subtitles it just buffers and CPU usage is at 49% in my DS218+, it kind of seems it is using software to transcode those instead of hardware but it is in fact showing it is using HW for transcoding.

I’ve tried with different movies in two different formats, H264 and HEVC (H265) (mkv files) and movies play fine without subtitles, but unfortunately we need subtitles.

This is happening with all my devices (AppleTV, Chromecast Ultra) in my gigabit wired lan.

Please help.

Thanks.

2

Image based subtitles (PGS, VOBSUB, etc) are a CPU-only operation.
The integrated Intel ASIC which does the transcoding does not support subtitle integration into the image.
PMS must take the output frame and overlay the subtitles on each frame as they come out.
This is what’s consuming the CPU time.

If you have them as SRT, SSA, or ASS (text based), most players can handle these natively and won’t need to be burned into each frame

3

Thank you, I’ve found some .srt files online and it’s now working, any Mac app suggestions to extract PGS subtitles from MKV files into SRT?

4

Quick search of Google came up with Mkvtoolnix. It’s the best remuxing tool going.

https://www.fosshub.com/MKVToolNix.html

I can’t speak to that site / version as I get it directly from the Fedora distribution files

5

Thanks very much.

6

First, this is the biggest problem I have with Plex. Even when the client can manage PGS subs with no issue, Plex will try to do it on the server. ChuckPA is right to recommend MKVToolNix but that will just remux your file. You’ll also need a way to turn your PGS subs into SRT or some other text-based format. A tool I use on OSX is called “subler” and it will OCR your subs and turn them into text. It works ok for most subs but if the subs are in italics or – heaven help you – a crazy font like the ones in Avatar the OCR will have hundreds of errors. You can clean these up manually (it’s time consuming) with good OSX subtitle editor. I use Aegisub for this. So the process is a bit burdensome – you extract the PGS stream using either Subler or MKVToolnix, then you let Subler OCR the resulting file. Then you save the SRT from Subler and open it in Aegisub to edit and correct. When you’re all done you can simply put the SRT in the same folder as the video stream.

7

Hi there,

I realise this is an old threat. I am also looking for a way to convert PGS / vobsub to .ASS / .SRT subtitle formats.

The reason is the manditory transcode wich is CPU / GPU heavy even with a I7-7700K and 1080ti on HEVC content tot 1080p (HEVC -> H264 (hw) ) . I have 10+ simultanious users and would like them to ‘direct stream’ more.

Is there a tool that can batch extract these subs from a MKV container and add them to the folder in .ass or .srt format. (2000+ movies)

8

Wouldn’t it be simpler to just use the “Find subtitle” feature in PMS to download someone else’s subs?

9

Already using auto-sub grabber subzero for srt subs. But my experience is that alot of subs are out of sync. While of a conversion of image based subs have a perfect sync.