Jellyfin is unable to play back Advanced Substation Alpha Subtitles on Chromecast

[justjanne]

Describe the bug
Jellyfin-Chromecast does not display Advanced SSA subtitles on Chromecast

To Reproduce

1. Select a movie with external Advanced SSA subtitles for playback on Chromecast

Expected behavior
The movie plays back with subtitles, as it does on Firefox, Chrome, and Android

Actual behavior
On Chromecast, no subtitles are shown

System (please complete the following information):

• OS: Docker
• Browser: Chromecast Gen. 1
• Jellyfin Version: 10.4.0
• Reverse proxy: kubernetes nginx-ingress

Additional context
The problem might be related to jellyfin/jellyfin#1896

[justjanne]

If preferred, I can privately share links to the files used, or can provide an account on the instance, to assist with bug reproduction and fixing.

[JustAMan]

This is most likely the issue with Chromecast app, so transferring.

[hawken93]

Hi,

I think this currently is working. At least with internal subs. Haven't tried external subs per your other ticket.

Could you check if it is still an issue?

Otherwise, maybe we can make this into a feature request for client side rendering?

[hawken93]

In favor if closing this, at this point chromecast cannot natively show ass subs but relies on server burn-in. As part of developing on the receiver I have seen that this works fine.

I'm assuming that this issue is with remux/transcode enabled because otherwise burnin cannot work. I think this is fixed.

If this issue is with remux/transcode disabled then chromecast will have no way of showing the subtitles currently. In that case it would be a feature request for native ass decoding on chromecast, although I doubt we'll be able to implement that seeing how for instance CCGTV uses a completely different media player from gen1-3, largely making the media player a black box that we cannot hack features into.
Assuming we were able to, the cpu on gen1-3 is already pretty congested so I'm not sure it packs the punch to actually do it.

It would probably work to reencode the subs to vtt and lose all the style information but it's been argued that we would rather burn them in than show them incorrectly.

[justjanne]

In favor if closing this, at this point chromecast cannot natively show ass subs but relies on server burn-in. As part of developing on the receiver I have seen that this works fine.

If this issue is with remux/transcode disabled then chromecast will have no way of showing the subtitles currently

I doubt we'll be able to implement that

I can understand why, but this is still quite annoying, considering just how much content tends to use Advanced SSA subtitles (even in situations where TTML would have been more than enough, with far more widespread industry support). I used to use this functionality pretty much all the time in the past, but I can understand why you wouldn’t want to support this in the future.

[hawken93]

That's okay, there are a few different approaches one could look at:

• If vtt subs can embed pictures, then the server could potentially rasterize subtitles and even convert raster subtitles to vtt subs based on images. Hopefully this would use native support in the chromecast
• Skip the style information and just convert to vtt.

I don't think we can get libass to do the same on chromecast that it does on web, due to the CAF black box. I should probably link this: https://developers.google.com/cast/docs/media and add that anything not on that list is not to be taken for granted.

As for this issue it should probably get a feature request label rather than bug label :)

[justjanne]

@hawken93 actually, vtt subtitles can’t contain images, but TTML subtitles can (that’s actually how Netflix does japanese subtitles), and creating those can be probably automated.