Playback fails for anime with ASS subtitles unless "Disable Subtitle Filtering" is turned off.

[solidsnakex37 55]

I'm running Emby inside Docker on Unraid, and I'm having a recurring playback issue related to ASS subtitle rendering, especially with anime content.

Here's what's happening:

• When "Disable Subtitle Filtering" is ON (toggle is green), playback fails or stalls on files that use detailed ASS subtitles.

• When "Disable Subtitle Filtering" is OFF (toggle is gray), playback works perfectly.

This feels backward. Based on the label, I expected the green toggle (enabled) to help playback by disabling some kind of subtitle filtering. But it turns out the filtering is actually needed to get playback working. So I think the labeling or behavior of this setting may be confusing or reversed.

• The setting resets every time the container restarts.
  I run weekly backups that restart all containers, and the Diagnostic Options (including subtitle filtering) always revert to default. This means I have to manually disable this setting every week or playback will break again.

• Fonts for ASS subs are not reliably available.
  Even if I map a custom fonts directory into Docker, Emby’s ffmpeg build doesn't seem to support using mounted fonts. This makes subtitle rendering unreliable unless it’s done on the client. But some clients, like browsers or apps on other platforms, can't render ASS properly without server help.

• Burning in subtitles is not a good workaround.
  Anime files often have multiple subtitle tracks: Forced, Full English, and Full Translated. Burning in the wrong one removes user choice and breaks accessibility for multi-language households.

• Please add a way to persist Diagnostic Options across Docker restarts.

• Please consider allowing Emby to load custom fonts from a volume like /config/fonts so ASS rendering works properly without having to rebuild ffmpeg.

If you have any suggestions on how I might be able to fix this, I am open to any suggestions. Thank you!

From: ffmpeg-transcode-be131e36-d487-4e80-bacc-65f43a255fa4_1.txt
 

Subtitle stream filtering disabled
...
[Parsed_ass_0 @ 0x7f86a2800980] fontselect: (default, 400, 0) -> /usr/share/fonts/truetype/dejavu/DejaVuSans.ttf, 0, DejaVuSans
...
[Parsed_ass_0 @ 0x7f86a2800980] Glyph 0x4e00 not found, selecting one more time
[Parsed_ass_0 @ 0x7f86a2800980] Glyph 0x500b not found, selecting one more time
...
Exiting normally, received signal 15

 

From: ffmpeg-transcode-0f0cb2a6-ba80-4bfe-abec-9b354b216827_1.txt

Subtitle stream filtering enabled
...
[Parsed_ass_0 @ 0x5588932e1a40] fontselect: (default, 400, 0) -> /usr/share/fonts/truetype/dejavu/DejaVuSans.ttf, 0, DejaVuSans
...
frame= 1895 fps= 59 q=28.0 size=    4096kB time=00:01:16.65 bitrate= 437.7kbits/s speed=2.37x
...
frame= 2844 fps= 61 q=28.0 size=    6144kB time=00:01:54.89 bitrate= 439.6kbits/s speed=2.36x
...
video:8416kB audio:1236kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.569141%

 

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ffmpeg-transcode-be131e36-d487-4e80-bacc-65f43a255fa4_1.txt ffmpeg-transcode-0f0cb2a6-ba80-4bfe-abec-9b354b216827_1.txt

[Luke 42077]

Hi, can you please attach the main emby server log as well?

Also, how does playing in Chrome compare? And as a test, if you disable hardware transcoding in server transcoding settings, how does that compare?

[Luke 42077]

Quote

Please consider allowing Emby to load custom fonts from a volume like /config/fonts so ASS rendering works properly without having to rebuild ffmpeg.

Good news. In the upcoming 4.9 server release, you should be seeing the embedded fonts within the file.

[Luke 42077]

But also, normally these subtitles are extracted on the fly. Did you also disable that in server transcoding settings?

[solidsnakex37 55]

10 minutes ago, Luke said:

Hi, can you please attach the main emby server log as well?

Also, how does playing in Chrome compare? And as a test, if you disable hardware transcoding in server transcoding settings, how does that compare?

Hey Luke! Sure thing, I attached a shortened version of the log, and the full log. 

This issue was experienced on a Samsung Smart TV, and I went to test it on my browser and ran into the same problem (FireFox). I just tested in Chrome, same issue happens. I attached that log as well. With hardware transcoding disabled the issue still occurs. 

When I turn off (enable) subtitle filtering, it works. 

 

23 minutes ago, Luke said:

But also, normally these subtitles are extracted on the fly. Did you also disable that in server transcoding settings?

I tested enabling this option as it was disabled, and this seems to work as well. I have had issues with this setting in the past in that subtitles won't ever appear for some media, but when I disable it the subtitles display just fine. This happens across a few devices, such as Chrome, Emby for Windows App, and my Samsung Tablet. So I just left it off. 

 

embyserver_shortened.txt embyserver_full.txt Hardware Transcode Disabled - Chrome.txt Chrome Test.txt

[Luke 42077]

OK personally I would leave that on, especially with the 4.9 release about to hit, when you use the extraction the web app will use the embedded fonts now.

Quote

subtitles won't ever appear for some media

generally this just means the extraction took too long. if that happens in your environment, then that would be the main reason to disable it.