Subtitles desync after every pause/resume on transcoded playback

[tirdg 1]

• Server: 4.9.5.0 (Linux)
• Client: Emby for Roku 4.1.65, Roku OS 15.2.4 (Roku Streaming Stick 4K)
• Playback: audio transcoded to AAC, video stream-copied (video reports as Direct Play), subtitles delivered as HLS

On transcoded playback, pausing and resuming causes the video to "jump back" and replay a few seconds, after which the subtitles are permanently out of sync for the rest of playback. It recurs on every pause/resume cycle and the jump back usually occurs within 30 seconds of resuming (Running out a client-side cache?). Selecting a different subtitle track during playback re-aligns everything until the next pause/resume cycle, at which point it happens again. If only one subtitle track exists, the video must be stopped and restarted to re-sync everything. 

The logs suggest that upon resume, emby relaunches the transcode process with a seek offset which is probably causing the noticeable jump back, but the subtitle stream doesn't get the memo. You also can't turn the current subtitle track "off and back on" as a solution. You have to do something that causes the server to re-issue the subtitle stream for the current position. So I guess turning off a subtitle track just disables the visual display but the stream stays alive somewhere and never gets corrected. Re-displaying it just shows the same stream with the same problem.

I'd prefer to send log files via PM. I have the server log for the time in question as well as four ffmpeg jobs. All available upon request.

[visproduction 367]

Known issue with media playback for audio.  Does this issue also cause subtitles to go out of sync?  Subs also rely on timecode to stay in sync. I think it could be the reason for getting out of sync after pausing.  Transcoding resetting the sync makes more sense because that would reset the timecode sync.
 https://watchtogether.watch/blog/why-video-is-out-of-sync

Is this sync issue inherent to the playback limitations for media files with pauses?  I am unsure anything can be done.

Edited 43 minutes ago by visproduction

[Luke 42870]

 

Hi there, let's look at an example. Please attach the information requested in how to report a media playback issue. Thanks!