[mythtv-users] Subtitle sync

[Ben Healy]

----- Original Message -----

> From: Ben Healy <melben1001 at yahoo.com.au>
> To: Discussion about MythTV <mythtv-users at mythtv.org>
> Sent: Saturday, 12 March 2016, 10:00
> Subject: Re: [mythtv-users] Subtitle sync
> 
> 
> 
> ----- Original Message -----
> 
>>  From: Michael T. Dean <mtdean at thirdcontact.com>
>>  To: Discussion about MythTV <mythtv-users at mythtv.org>
>>  Sent: Friday, 11 March 2016, 22:51
>>  Subject: Re: [mythtv-users] Subtitle sync
>> 
>>  On 03/11/2016 01:09 AM, Ben Healy wrote:
>>>   From: Jean-Yves Avenard
>>> 
>>>>   On 10 March 2016 at 13:39, Ben Healy wrote:
>>>> 
>>>>>     Hi All
>>>>> 
>>>>>     I posted something in the forum but had no luck so trying on 
> the 
>>  mailing
>>>>>   list.
>>>>>     I was using myth 0.27.6, now upgraded to 0.28 from mythbuntu 
> ppa 
>>  on an ASUS
>>>>>   celeron chromebox with intel graphics.
>>>>>     I'm in Australia recording DVB which uses Teletext 
> subtitles.
>>>>> 
>>>>> 
>>>>>     The issue I'm facing is the Teletext subtitles are 
> appearing 
>>  slightly
>>>>>   ahead of the video/audio, so on a scene with a lot of quick 
>>  dialogue the
>>>>>   subtitles have been and gone before the person speaks.
>>>>> 
>>>>>     I am seeing this issue with 0.27 and 0.28. I setup another 
>>  frontend on a PC
>>>>>   with better specs and an nvidia card and saw the same issue.
>>>>>     I see reference to a TOGGLESUBDELAY action in the wiki and 
>>  it's
>>>>>   referenced in the menu_playback.xml file, but when subtitles 
> are 
>>  enabled that
>>>>>   menu item doesn't appear. I also can't find it in the 
>>  frontend playback
>>>>>   keybindings. I presume I could fix my issue with this if I 
> could 
>>  find this
>>>>>   setting.
>>>>   Press Menu , select Subtitles. From there's there's an 
> Adjust 
>>  entry.
>>>>   You can set the delay +/- 5s
>>>   When I press Menu, select Subtitles, I don't have an entry to 
> adjust 
>>  the delay. There is an entry to adjust zoom, but not delay.
>>> 
>>>   I'm using the Blue Abstract Theme, but I've switched to a few 
> other 
>>  themes and the behaviour is the same for me.
>> 
>>  The option to adjust subtitle delay is only shown (meaning only usable) 
>>  for text subtitles and raw text subtitles, not for teletext 
>>  captions/menus nor NTSC/ATSC captions nor DVD subtitles/menus nor AV 
>>  subtitles.  This is why it's there for external subtitles (srt).
>> 
>>  This is also why it's not a key binding--because it only applies for a 
>>  limited subset of subtitle types, so allowing the user to display it 
>>  whenever would imply it would work whenever (and ignoring their request 
>>  to do something wouldn't be user friendly).  Therefore, it's only 
>>  accessible via the menu, which is dynamically generated to only show the 
>>  option when it can be applied.
>> 
>>  Mike
>> 
> 
> 
> Thanks Mike for the explanation of why I can't see the subtitle delay menu 
> option and keybinding.
> 
> Thanks JYA for confirming that Teletext subtitles are in sync for you.
> 
> It must be something to do with the configuration of my system, so I'll look 
> into it further but if anyone has any suggestions as to what logging options 
> might help I would appreciate it.
> 
> Thanks
> 

> Ben

I did a bit more testing with 3 different frontends:
1. Chromebox - subtitle ahead of video with VAAPI and OpenGL Normal, OpenGL Normal is slightly worse
2. Desktop with Nvidia 8600GT - subtitles ahead of video with OpenGL normal, but with VDPAU HQ, the subtitles are almost in sync.
3. Raspberry Pi 2 - subtitles in perfect sync with OpenMAX normal. I tried other profiles and it looks like the subtitles are ahead with Slim, but it's hard to tell as playback is quite choppy.

So I would appreciate if someone could try playback with DVB Teletext Subtitles on the OpenGL Normal profile and see if they also see the sync issue.


I realise I must be in a small minority - users of subtitles would be fairly low, countries that use teletext subtitles even lower and then users who are not using nvidia are probably lower again.

Ben