Subtitles going out of sync when transcoding sound

[Luke 40065]

14 hours ago, psxlover said:

ssa subtitles issue introduced in .79, so I guess I'll open another thread for it when I get the chance to gather logs (unless if someone else reproduces it/posts logs).

Regarding that, can you try this version? Thanks.

tizen.zip

[psxlover 31]

Hallo Luke. That didn't fix the ssa subtitle issue

[Luke 40065]

Ok thanks for the info.

[psxlover 31]

As I posted in the other thread as well, the .ssa issue is fixed with the latest version.

Srt subtitles going out of sync when transcoding audio is still an issue though.

[Luke 40065]

Thanks for the feedback. Still trying to chase down the subtitle sync.

[psxlover 31]

Just tried the video in a Mi Box (Android TV).

It also reports that it is a direct stream, with the transcode reason being "Unsupported audio" in stats for nerds, but there there is no desyncing.

What I noticed though, was that when I seek backwards, sometimes the picture stays frozen for a couple of seconds while the audio is playing, and the picture starts playing when the audio and subtitles reach the point where the picture is frozen. I'm guessing the video player used is freezing the video until the audio catches up, and in the mean time the subtitles are also synced. But the player of the TV doesn't do anything like that, it start playing from the point that the video is when seeking back (with the audio being in sync with the video), but the subtitles at where the video would have been if seeking was exactly 10s.

Comparing the timestamps in the .srt with what I see, the subtitles seem to show up on the correct time reported by the application.
So it seems it is indeed the application that is out of sync with the video.

[psxlover 31]

Another issue I noticed, is that if I cast the video from my phone to the TV using DLNA, the audio is not transcoded, resulting in the TV showing a message that the audio is not supported and that it will play without audio.

Also Android TV's stats for nerds contains more information about the transcode, showing information about both the original and the transcoded stream, along with the reason for the transcode, something that is missing from Samsung TV application's stats for nerds.

[Carlo 4552]

30 minutes ago, psxlover said:

Just tried the video in a Mi Box (Android TV).

It also reports that it is a direct stream, with the transcode reason being "Unsupported audio" in stats for nerds, but there there is no desyncing.

What I noticed though, was that when I seek backwards, sometimes the picture stays frozen for a couple of seconds while the audio is playing, and the picture starts playing when the audio and subtitles reach the point where the picture is frozen. I'm guessing the video player used is freezing the video until the audio catches up, and in the mean time the subtitles are also synced. But the player of the TV doesn't do anything like that, it start playing from the point that the video is when seeking back (with the audio being in sync with the video), but the subtitles at where the video would have been if seeking was exactly 10s.

Comparing the timestamps in the .srt with what I see, the subtitles seem to show up on the correct time reported by the application.
So it seems it is indeed the application that is out of sync with the video.

What happens if you turn off subs, then turn back on again midway through the movie?  Out of sync or in sync?

[psxlover 31]

Yes.

Even with the subtitles off, I can see that the same scene/line appears in different time between seeks.

[Carlo 4552]

Not sure what that means.  In sync or out of sync?

[psxlover 31]

Out of sync. As I said above (and also mentioned in the first post), it's the timestamp the application has that is out of sync, the subtitles just appear based on that timestamp.

And the same scene is displayed with different timestamp if I seek back and forth a few times.

[psxlover 31]

@Luke it's not the correct forum, but since the issue is the same I'll write here.

The same issue exists on the LG application. If audio is being transcoded and you move the video, there is a high chance that the subtitles will go out of sync (haven't checked if the timestamp the application shows is also out of sync with the audio/video and in sync with the subtitles). There is also a small chance that when moving the video the subtitles will get back in sync.

[SamES 1004]

15 minutes ago, psxlover said:

@Luke it's not the correct forum, but since the issue is the same I'll write here.

The same issue exists on the LG application. If audio is being transcoded and you move the video, there is a high chance that the subtitles will go out of sync (haven't checked if the timestamp the application shows is also out of sync with the audio/video and in sync with the subtitles). There is also a small chance that when moving the video the subtitles will get back in sync.

Is it the same specific titles on both TV's?  It could be an issue with the actual files.  I can't recall if anyone else has reported this same issue

[psxlover 31]

It's not an issue with the subtitles, as I said they work perfectly fine if I see the videos from start to finish without moving forward/backwards. Furthermore I was able to reproduce it with a file that had both an audio track that needed transcoding (TrueHD) and an audio track that played as is, and while subtitles would get out of sync when moving forward/backwards while transcoding, they would always stay in sync when using the audio track that didn't require transcoding.

I did find though another file with TrueHD that did not get out of sync no matter how much I moved around the video.

[SamES 1004]

11 hours ago, psxlover said:

I did find though another file with TrueHD that did not get out of sync no matter how much I moved around the video.

So this gives some confidence that it can work correctly

11 hours ago, psxlover said:

It's not an issue with the subtitles, as I said they work perfectly fine if I see the videos from start to finish without moving forward/backwards. Furthermore I was able to reproduce it with a file that had both an audio track that needed transcoding (TrueHD) and an audio track that played as is, and while subtitles would get out of sync when moving forward/backwards while transcoding, they would always stay in sync when using the audio track that didn't require transcoding.

It may be that there is some issues with timing in the file, so it works fine when played consecutively, but jumping around causes issues.

Can you confirm when you say Transcoding, is it transcoding, or is it really DirectStream (ie: only the audio is being converted)?

I couldn't confirm from your response, is it only the one file, or many files that have this issue?

Can you post the media info from the details screen on the server for the file that has an issue and the one with TrueHD that works correctly?

[psxlover 31]

1 hour ago, SamES said:

Can you confirm when you say Transcoding, is it transcoding, or is it really DirectStream (ie: only the audio is being converted)?

Sorry for confusing you. Only the audio is being transcoded (so DirectStream), the video is transferred as is so it is not that the subtitles are burned in the video. I'm pretty sure that the video is not being transcoded because my server can't even handle playback of the files, let alone transcode the video.

I attached the media info from three files, one where the subtitles never go out of sync (The Martian) and two where the issue is observed. As you can see "The Martian" and "Blade Runner 2049" are pretty much the same apart from the software versions that were used for creating them. On Blade Runner when using the TrueHD audio track the subtitles go out of sync, while using the second audio track (AC3 5.1 English) the subtitle stay in sync with the audio&video.

"The Expanse" is the one where I first noticed this (not just that episode but all DTS episodes I had), and it is the one where I confirmed that not just the subtitles but also the timestamp reported by the application was wrong/out of sync with the video.

Blade Runner 2049 (2017) Bluray-2160p.mkv.MediaInfo.txt The Martian (2015) Bluray-2160p.mkv.MediaInfo.txt the.expanse.s02e13.1080p.bluray.x264-rovers.mkv.MediaInfo.txt

Edited December 17, 2021 by psxlover

[SamES 1004]

One of the issues with the Martian might be the number of subtitle tracks.  The Samsung internal player has issues with too many tracks.  You can use MkvToolNix to copy the video, audio and just some of the required sub tracks to a new file (it will be quick, it's just a direct stream copy, no conversion) and see if it is any better.

You could also try this with the Expanse (in this case, just copy all tracks) to a new container, and see if this makes a difference.  It will force the container headers to be rewritten which may improve it, and also may not.

[KahanBhalani 0]

On 17/12/2021 at 02:19, psxlover said:

@Luke it's not the correct forum, but since the issue is the same I'll write here.

The same issue exists on the LG application. If audio is being transcoded and you move the video, there is a high chance that the subtitles will go out of sync (haven't checked if the timestamp the application shows is also out of sync with the audio/video and in sync with the subtitles). There is also a small chance that when moving the video the subtitles will get back in sync.

Any updates on this issue? I am also facing this with the LG Emby app.

[Luke 40065]

On 5/7/2024 at 1:51 AM, KahanBhalani said:

Any updates on this issue? I am also facing this with the LG Emby app.

Hi, we are looking into this. Thanks.

[bjerne 15]

On 08/05/2024 at 23:13, Luke said:

Hi, we are looking into this. Thanks.

Any news, @Luke?

Having to exit out of video playback and restart to ensure subtitles being in sync feels clunky to say the least

Maybe there is some work around that we could use until you guys have a fix (which has been in the works for 4 years now?)

[Luke 40065]

On 12/14/2024 at 1:06 PM, bjerne said:

Any news, @Luke?

Having to exit out of video playback and restart to ensure subtitles being in sync feels clunky to say the least

Maybe there is some work around that we could use until you guys have a fix (which has been in the works for 4 years now?)

HI, we are working on this. Thanks.