AndroidTV Jellyfin Ass subtitles artifacts

[krulaks]

As in title. Using newest Jellyfin for android tv with ASS subs results in artifacts every like 10 seconds.

This happens usually with anime, I know that this happens because of transcoding since Jellyfin tv does not support these kind of subtitles. Question is why it produces artifacts? - it looks like sudden bitrate drop on part of image or like a pixel shift for fraction of seconds.

EDIT:
Tested same video on iPhone for via chrome and switched lower mbps to trigger transcoding and there are no artifacts while using same subtitles. So I guess burning subtitles via transcoding produces these issues.
These artifacts are fixed in time - always on 3:25 on said video for example.

ASS transcoding:


Without ASS transcoding:

[Efficient_Good_5784]

Can you share images of both a normal scene and then of a scene with the artifact(s)?

[krulaks]

Can you share images of both a normal scene and then of a scene with the artifact(s)?

Added images to the post. Sorry for photo instead of screenshot (idk how to do them on tv).
You can see some kind of shift/blur effect on hair on the left.
I can add more examples if needed

[TheDreadPirate]

What are the server specs? I'm guessing this has an AMD GPU in it?

[krulaks]

What are the server specs?  I'm guessing this has an AMD GPU in it?

no dedicated gpu, using intel igpu - i5-12600K

This doesn't seem like a gpu issue since transcoding not related to subtitles does not generate such issues.

[TheDreadPirate]

What OS? Can you share the ffmpeg log when the subtitles were burned in? There shouldn't be any noticeable difference with and without subtitle burn in.

[krulaks]

Sorrry for late reply, but now I see that it may be not related to the transcoding. With different anime - without subtitles and Jellyfin reports direct transmission - there are different kind of artifacts - this time it also freezes visuals for a second or two. No error or warnings in Jellyfin logs

Tested same episode on PC, mobile iOS, mobile android and it works fine.

So I guess Android TV version is scuffed and buggy and that’s it

[TheDreadPirate]

Android TV does not support ASS subs, so it is being transcoded with burned in subtitles. PC (both browser and JMP) fully supports ASS subs, mobile Android and mobile iOS have partial ASS support. Android will support unstyled ASS subs with the integrated player and full ASS subs with the web player. I think it is similar with iOS (I don't have any Apple devices).

Does this artifacating happen with all videos or just some? Is your CPU overclocked?

The subtitle burn-in process is a bit different than standard transcoding.

GPU decodes video frame -> CPU composes and burns in subtitles -> GPU encodes frame

And can you share your ffmpeg log via privatebin.net?