U4: Subtitles out of sync with video

[Andrew-L]

I have found what appears to be a serious failure of the U4 to correctly display subtitles. The problem occurs when replaying a recorded program. When the recorded program starts playing the subtitles are displayed in sync with the video for about 15 seconds and then they get completely out of sync to the point where it is completely unusable. If you skip forwards or backwards 10 seconds the captions will again display correctly for about 15 seconds before going out of sync again. This issue has been observed on all recordings and on multiple channels ABC, Seven, Nine and Ten.

The problem also occurs if you pause live TV. If you pause live TV for 60 seconds and then start playing it again the subtitles are displayed in sync with the video for between 15 and 30 seconds before becoming unsynchronised.

Also if you start replaying a recording while it is still being recorded, the subtitles start out synchronised before becoming unsynchronised.

I have loaded the latest firmware to the U4. I have tried changing the two subtitle delays from No delay to 0.5 sec and 3 sec but this does not fix the problem. I have now set them for No delay which is the factory setting.

Please test the issues I have described before offering advice.

[prl]

How much is the subtitle timing out by?

I can't reproduce this problem on a T4 (firmware 20171230) on timeshifted 9Gem or SBS ONE.

[Andrew-L]

How much is the subtitle timing out by?

I can't reproduce this problem on a T4 (firmware 20171230) on timeshifted 9Gem or SBS ONE.

When replaying last night's channel 7 news the captions were so far out of sync they were displaying captions for the next news segment while the current news segment played. It is difficult to measure the exact time difference but it could easily be 30 seconds to a minute. So it is totally unusable at the moment.

[prl]

How much is the subtitle timing out by?

I can't reproduce this problem on a T4 (firmware 20171230) on timeshifted 9Gem or SBS ONE.

When replaying last night's channel 7 news the captions were so far out of sync they were displaying captions for the next news segment while the current news segment played. It is difficult to measure the exact time difference but it could easily be 30 seconds to a minute. So it is totally unusable at the moment.

Captions on live broadcasts are typed in on the fly. They're often way out of sync (and often have unintentionally amusing errors). The sync isn't changed by recording and playback (which is also what timeshift does). The time codes for the subtitles aren't changed by recording and playback. This is a feature, not a bug.

What about on pre-recorded sources like TV series or movies?

[Andrew-L]

How much is the subtitle timing out by?

I can't reproduce this problem on a T4 (firmware 20171230) on timeshifted 9Gem or SBS ONE.

When replaying last night's channel 7 news the captions were so far out of sync they were displaying captions for the next news segment while the current news segment played. It is difficult to measure the exact time difference but it could easily be 30 seconds to a minute. So it is totally unusable at the moment.

Captions on live broadcasts are typed in on the fly. They're often way out of sync (and often have unintentionally amusing errors). The sync isn't changed by recording and playback (which is also what timeshift does). The time codes for the subtitles aren't changed by recording and playback. This is a feature, not a bug.

What about on pre-recorded sources like TV series or movies?

As I watch captions 100% of the time while watching TV I am familiar with the difference between live captions (with their typos) and pre-captioned programs. I just tested it on a recording of Dr Who from yesterday afternoon, same fault, subtitles ok for 15 seconds then they get out of sync. I have also done a full shutdown, then power off, wait and restart - no change to the symptoms.

Jai has just told me that the issue wasn't there with previous models so it has been referred to the software guys. Thanks Jai, much appreciated.

[peteru]

Is the sync error always in the same direction? Are subtitles always drifting ahead / behind? Are they drifting by a constant ratio or is it a big discontinuous jump? For example, subtitles slowly drift ahead at a rate of 10 seconds for every minute of playback?

[Andrew-L]

Is the sync error always in the same direction? Are subtitles always drifting ahead / behind? Are they drifting by a constant ratio or is it a big discontinuous jump? For example, subtitles slowly drift ahead at a rate of 10 seconds for every minute of playback?

After the initial 15 seconds of synchronised subtitles, sometimes I have noticed a break in the subtitles before they start displaying subtitles that are ahead of the video. It is a hard thing to measure what it's doing over time but at times the subtitles look like they are going at double speed or more. It is unwatchable by then so I usually give up. The subtitles always end up ahead of the video as far as I can tell.

This bug has been referred to the Software experts.

[Grumpy_Geoff]

...
This bug has been referred to the Software experts.

You were just replying to one of the software experts

[MrQuade]

I just tested this in timeshift mode.

If timeshifting only 5-10 seconds behind live TV, then there is no problem at all as far as I saw.

When I skipped back further into the file, that is when the problems started.
The subs are in sync for about 10-15 seconds or so, and then the subs jumped ahead of the video by about a minute or so (sorry for being imprecise, if you wan't better info I am going to have to break out a stopwatch ). The subs that were being displayed were definitely not from live TV, but from a point somewhere short of the end of the timeshift file.

[prl]

...
If timeshifting only 5-10 seconds behind live TV, then there is no problem at all as far as I saw.
...

Then that's probably why I didn't see the problem when I tried to replicate it.

[Andrew-L]

... The problem occurs when replaying a recorded program. When the recorded program starts playing the subtitles are displayed in sync with the video for about 15 seconds and then they get completely out of sync to the point where it is completely unusable. If you skip forwards or backwards 10 seconds the captions will again display correctly for about 15 seconds before going out of sync again. This issue has been observed on all recordings and on multiple channels ABC, Seven, Nine and Ten.

The problem also occurs if you pause live TV. If you pause live TV for 60 seconds and then start playing it again the subtitles are displayed in sync with the video for between 15 and 30 seconds before becoming unsynchronised.

Also if you start replaying a recording while it is still being recorded, the subtitles start out synchronised before becoming unsynchronised....

The original bug report describes the three scenarios (one per paragraph - quote above) where there are problems with out of sync subtitles. If you try them as described you should see the bug. Just to clarify one issue, when I say jump forwards or backwards 10 seconds I am pressing the left or right navigation buttons.

[Coalminer]

Yes, my U4 does the same
plays in sync on pre-recorded files for about 10-15 secs then jumps forward roughly about 1 min. All channels
If I jump forward or back it stays in sync for another 10 secs then jumps forward.
Totally useless at present

[Andrew-L]

Has there been any progress on fixing this bug? Once the subtitles go out of sync they end up about 30 seconds ahead of the video for the duration of the program. This makes it impossible to use the PVR to replay recordings with subtitles. I live in a household that relies on subtitles so if this bug isn't fixed the PVR is useless.

[Coalminer]

Has there been any progress on fixing this bug? Once the subtitles go out of sync they end up about 30 seconds ahead of the video for the duration of the program. This makes it impossible to use the PVR to replay recordings with subtitles. I live in a household that relies on subtitles so if this bug isn't fixed the PVR is useless.

I agree

[MrQuade]

The latest beta online update looks like it has fixed this subtitle sync problem.

I gave it a quick test in timeshift and on a recording and it works for me.

[Andrew-L]

The latest beta online update looks like it has fixed this subtitle sync problem.

I gave it a quick test in timeshift and on a recording and it works for me.

That's good to hear and thanks for the instructions in the Public Beta forum about how to obtain a copy of the latest beta version. If the subtitle fix is going to be released for general download soon I will wait for that. Does anyone know when that will be?

[peteru]

Generally I will release a fix once it has been verified to work well enough and there is no evidence of other regressions. It would be handy if the people who were affected by the issue would actually test the fix. The less feedback on testing I receive, the longer it will be before I am confident to make a general public release. Could be days, could be weeks.

[Andrew-L]

With the latest software released today, the subtitle bugs I first reported on 16 Jan 2018 appear to be fixed. I have retested all items listed in the initial bug report and the subtitles on the U4 are now working as expected. Thank you to all involved in fixing this issue. Now I can use the U4 as a PVR not just a set top box and I can go back and watch some of the recordings I have done in the last two weeks.

As our household use subtitles on the PVR all the time, when they fail we notice it immediately as we can't follow or enjoy the program. I will provide further feedback or bug reports if I notice any other issues. There may be other little issues but so far it's looking very good!

[peteru]

Thanks for the feedback. Glad my efforts were worth it and fixed the issue for you.

[hypoxia88]

The beta-upgrade fix worked! Previously my two U4s had subtitles accelerating to 40 seconds to soon. Applied beta update fix to one. It appears to work as it should, with subtitles roughly in sync with speech. Fix works with recordings made before fix was applied. Will apply fix to the other, and not post further about this issue if the fix works on that also.
Thank you.

[Coalminer]

Hi
I have been away from home since this was fixed and as such have not yet attempted the upgrade
Just went to the software manager and searched for latest update and it states the update is 146 files and should consider a usb update instead but gives the online update option
Will it be OK to do an online update?

[prl]

Hi
I have been away from home since this was fixed and as such have not yet attempted the upgrade
Just went to the software manager and searched for latest update and it states the update is 146 files and should consider a usb update instead but gives the online update option
Will it be OK to do an online update?

Yes, but you may want to do a USB install of firmware 20180216 instead. I think that should have the subtitle synch fixes.

If it doesn't, you could switch to the beta update feed and see if more recent betas fix the problem, but I don't think they contain anything relevant to the subtitle synch problem.

[Grumpy_Geoff]

Hi
I have been away from home since this was fixed and as such have not yet attempted the upgrade
Just went to the software manager and searched for latest update and it states the update is 146 files and should consider a usb update instead but gives the online update option
Will it be OK to do an online update?

If it was me, I'd take a backup first, then do the online update. If that update fails, then I'd be loading the 20180216 image.
I'm pretty sure the subtitle fix was released to the general feed in early Feb., so this online update should include it.

[Coalminer]

Thanks folks
I will give it a go and see what happens

[Coalminer]

OK done the online update and the only change is that after about 60 secs the subtitles disappear altogether
Now to try the USB update and hope it also allows the U4 and T4 to see each other over the network

[Coalminer]

Happy to report 20180216 image has fixed the subtitle problem and also the network problem as well
Good work guys