[mythtv-users] Mythfrontend failing to display subtitles for some type of file

[Paul Gardiner]

On 04/09/2022 15:28, Paul Gardiner wrote:
> On 04/09/2022 14:34, John Pilkington wrote:
>> On 04/09/2022 13:36, Paul Gardiner wrote:
>>> One further discovery: if I demux the orifinal file to produce two 
>>> files, one containing combined video and audio, the other (a .srt 
>>> file) containing just the subtitles, mythfrontent displays the 
>>> subtitles without problem. The logs suggest this mode uses a very 
>>> different code path, so the experiment didn't help track down the cause.
>>>
>>> I wonder if, in the failing case - without demuxing, the subtitles 
>>> are being displayed off screen or with opacity 0. Perhaps it's 
>>> silently failing to load a font. The logs show events as each 
>>> subtitle should be displayed.
>>>
>>> At the moment I can't think of a way to track this down further.
>>
>> I habitually drop subtitles, so don't have much practical experience; 
>> but your posted log included
>>
>> AFD: ScanATSCCaptionStreams() called with no PMT
> 
> Yes, I did notice that eventually, after having wrongly posted that 
> there were no errors. The strange thing is that mythfrontend still 
> offers the option to enable/disable these subtitles during playback and 
> some sort of libass event occurs as the time of each phrase is reached. 
> I suppose it's a possibility that - due to that error above - 
> mythfrontend is setting itself up unable to respond to those events.
> 
>> which doesn't look good.
>>
>> I posted my 'typical' remux command line on the dev list on Tuesday.  
>> It migh be worth adding an 'scodec copy' phrase to that;  and use 
>> mythffmpeg...
> 
> Thanks. That's a possibility I guess. My current work around is to use 
> leanfront instead for this type of file, but then it's a pain not to 
> have a simple toggle button for subtitle on/off.

It turns out that, installed on another machine, mythfrontend shows the 
subtitles. For my "production" frontend, I build the disc image using a 
program called kiwi-ng. That builds a minimal system, so if my 
mythfrontend package has missing dependencies they wont be installed. 
Also I build my own packages, so missing dependencies are not unlikely. 
It may just be a commonly used package of fonts I need, or something 
like that.