Kodi 20: DVB subtitles position

[Dis90]

Bug report

Describe the bug

Here is a clear and concise description of what the problem is:
Sometimes DVB subtitles aren't displayed correctly.

Both lines in example picture should be leveled to left. Instead second lines starts different position than first line. Kodi 19 and VLC displays subtitles correctly.

Expected Behavior

Here is a clear and concise description of what was expected to happen:

Actual Behavior

Possible Fix

To Reproduce

Steps to reproduce the behavior:

Debuglog

The debuglog can be found here:
kodi.log

Screenshots

Here are some links or screenshots to help explain the problem:

Kodi 19:

Kodi 20:

Additional context or screenshots (if appropriate)

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Your Environment

Used Operating system:

• Android

• iOS

• tvOS

• Linux

• OSX

• Windows

• Windows UWP

• Operating system version/name:

• Kodi version: 20

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[enen92]

@Dis90 any chance you can provide a short video sample that illustrates the issue?

[Dis90]

Sure. Here's 5 min clip of same video used in screenshots. https://drive.google.com/file/d/1iK5SSIcwrE9AIbkZoRHoLrcOSr-MDNzM/view?usp=sharing

[enen92]

@CastagnaIT maybe you can take a look at this? Should be an easy fix

[CastagnaIT]

i have lost 3 hours without find nothing useful/wrong in code i have no idea

[enen92]

I think I've come across a similar issue in the past when fixing/looking into Ass subtitles (old implementation). IIRC the source of the problem was that we were creating 2 different overlays (one per line).
I'll take a look when possible to check if I can find the root cause.

[CastagnaIT]

i have noticed that if put video in pause and you resize the window to the source res sub size (576x720 if i remember correctly) the text become correct
so i suspected something in the scale calculation i have tried change in different ways without success

[CastagnaIT]

I have done other tests, i think to be close to the solution so the problem seem around the scale,
the text now seem aligned correctly also after resizing kodi window:

but now is not centred correctly and i do not understand where is the mistake

if you want try it this is my changes: CastagnaIT@80dd84f
maybe you see where i am wrong

in addition to the test file provided above suggest to test also with the PGS sample that you can find in the FTP directory:
/Samples_new/Subtitles/PGS/PGS_StretchingTest.mkv
this is good to verify that the subs are displayed centred correctly

[Dis90]

Looking your screenshot I think subtitles are in correct place. It is very common at least here in Finland that DVB subtitles are aligned to left instead of center.

Edit. in fact, I'm not sure about the subtitles for this channel...
Let me know if you need sample video of recording from different channel which I know for sure to have subtitles aligned to left.

[CastagnaIT]

i think to have found the solution
i will try to prepare a PR

[enen92]

Fixed by #20794

[Dis90]

@CastagnaIT I updated to latest Kodi 20 and this issue is happening again.

[Dis90]

@enen92 Sorry for bumping this but should I open new issue?

[enen92]

@Dis90 is this a fallback from a recent subtitles PR (#21162) or is it still broken right after #20794 has been merged?
Maybe you can manage to check a previous build or move back before #21162 went in?

[Dis90]

@enen92 I tested with builds from here http://mirrors.kodi.tv/nightlies/osx/x86_64/master/
Subtitles are working correctly in kodi-20220325-4734091c-master-25035-x86_64.dmg but not in kodi-20220327-f0125d68-master-25058-x86_64.dmg So I'm pretty sure that PR #21162 is causing this problem.

[CastagnaIT]

sorry i lost the message notification tag on hundreds of emails
your sample have 4/3 subtitles resolution on a 16/9 video resolution, that's why now doesn't work
maybe we should allow this "mix" use case to use ALIGN_VIDEO in some way

PS. reading DVB spec its a regular use case have a SD 4/3 sub on fullhd video