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

Paul Gardiner lists at glidos.net
Sun Sep 4 14:28:09 UTC 2022

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.


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