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

[Paul Gardiner]

When I playback programs I've recorded from terrestrial channels, 
subtitles work perfectly but for downloaded files, they commonly 
(perhaps always) don't. These are files for which Leanfront displays the 
subtitles fine.

Here's an example format as displayed by ffmpeg:

Input #0, matroska,webm, from 'Movie.mkv':
   Metadata:
     ENCODER         : Lavf59.16.100
   Duration: 01:05:36.45, start: 0.000000, bitrate: 1663 kb/s
     Stream #0:0: Video: hevc (Main), yuv420p(tv, bt709, progressive), 
1920x1080 [SAR 1:1 DAR 16:9], 23.98 fps, 23.98 tbr, 1k tbn, 23.98 tbc 
(default)
     Metadata:
       ENCODER         : Lavc59.18.100 libx265
       DURATION        : 01:05:36.438000000
     Stream #0:1(eng): Audio: ac3, 48000 Hz, 5.1(side), fltp, 448 kb/s 
(default)
     Metadata:
       ENCODER         : Lavc59.18.100 ac3
       DURATION        : 01:05:36.448000000
     Stream #0:2(eng): Subtitle: subrip
     Metadata:
       DURATION        : 01:02:56.235000000


While watching, when I enable subtitles, I see this in the logs (no errors):


2022-09-03 16:33:36.318974 I [1393/1393] CoreContext 
captions/subtitlescreen.cpp:2365 (myth_libass_log) - libass: Shaper: 
FriBidi 0.19.6 (SIMPLE) HarfBuzz-ng 2.6.4 (COMPLEX)
2022-09-03 16:33:36.338660 I [1393/1393] CoreContext 
captions/subtitlescreen.cpp:2365 (myth_libass_log) - libass: Using font 
provider fontconfig


I build from source, so I wonder if I'm failing to include something in 
the build. Here's the config

[   99s] #### MythTV CONFIGURATION ####
[   99s] # Basic Settings
[   99s] Qt minimum version        5.9
[   99s] Qt installed version      5.15.2
[   99s] Compile type              release
[   99s] Compiler cache            yes
[   99s] DistCC                    no
[   99s] qmake                     /usr/bin/qmake-qt5
[   99s] install prefix            /usr
[   99s] runtime prefix            /usr
[   99s]
[   99s] CPU                       x86 x86_64 (model name	: AMD EPYC 
7301 16-Core Processor)
[   99s] standalone assembly       yes
[   99s] x86 assembler             nasm
[   99s] MMX enabled               yes
[   99s] MMXEXT enabled            yes
[   99s] 3DNow! enabled            yes
[   99s] 3DNow! extended enabled   yes
[   99s] SSE enabled               yes
[   99s] SSSE3 enabled             yes
[   99s] AESNI enabled             yes
[   99s] AVX enabled               yes
[   99s] AVX2 enabled              yes
[   99s] XOP enabled               yes
[   99s] FMA3 enabled              yes
[   99s] FMA4 enabled              yes
[   99s] i686 features enabled     yes
[   99s]
[   99s] Creating configuration files ...
[   99s]
[   99s] # Input Support
[   99s] Joystick menu             yes
[   99s] lirc support              yes
[   99s] libCEC device support     yes [/usr/include]
[   99s] Video4Linux support       yes
[   99s] FireWire support          no
[   99s] DVB support               yes [/usr/include]
[   99s] DVB-S2 support            yes
[   99s] HDHomeRun support         yes
[   99s] Sat>IP support            yes
[   99s] V at Box TV Gateway support  yes
[   99s] Ceton support             yes
[   99s] DVEO ASI support          no
[   99s]
[   99s] # Sound Output Support
[   99s] PulseAudio support        no
[   99s] OSS support               yes
[   99s] ALSA support              yes
[   99s] JACK support              default
[   99s] libfftw3 support          yes
[   99s]
[   99s] # Video Output Support
[   99s] x11/xrandr support        yes
[   99s] VDPAU support             yes
[   99s] NVDEC support             yes
[   99s] VAAPI support             yes
[   99s] DRM support               yes
[   99s] DRM Qt integration        no
[   99s] Video4Linux codecs        yes (DRM yes)
[   99s] MMAL decoder support      no
[   99s] OpenGL                    yes (OpenGLES no)
[   99s] EGL support               yes
[   99s] Vulkan                    no (libglslang no)
[   99s] MHEG support              yes
[   99s] libass subtitle support   yes
[   99s]
[   99s] # Misc Features
[   99s] Frontend                  yes
[   99s] Backend                   yes
[   99s] Qt private headers        no
[   99s] Wayland extras            no
[   99s] multi threaded libavcodec yes
[   99s] libxml2 support           yes [/usr/include/libxml2]
[   99s] libdns_sd (Bonjour)       yes
[   99s] libcrypto                 yes
[   99s] gnutls                    no
[   99s] exiv2 support             yes (internal)
[   99s] udfread support           yes (internal)
[   99s] bluray support            yes (system)
[   99s] systemd_notify            yes
[   99s] systemd_journal           yes
[   99s]
[   99s] # Bindings
[   99s] bindings_perl             yes
[   99s] Perl config options       INSTALLDIRS=vendor
[   99s] bindings_python           yes
[   99s] bindings_php              yes
[   99s]
[   99s] # External Codec Options
[   99s] mp3lame                   yes
[   99s] xvid                      no
[   99s] x264                      no
[   99s] x265 (HEVC)               no
[   99s] vpx                       no
[   99s] libaom   (AV1)            no
[   99s] libdav1d (AV1)            no
[   99s]
[   99s] # Compilation Options
[   99s] C++ standard supported    c++17
[   99s] Enforce c++11 nullptr     yes
[   99s] Enforce shadowed vars     yes


Anyone have any ideas as to what I might try to fix this?

Cheers,
	Paul.