我正在运行 Ubuntu 18.04.3，并通过 PPA 安装 Gnome-subtitles 1.6，如下所示
sudo add-apt-repository ppa:pedrocastro/ppa
sudo apt-get update sudo
apt-get install gnome-subtitles
因为它们不再存在于 Ubuntu 18.04 中。
有时，打开 *.srt 字幕时，Gnome Subtitles 会显示“无法播放文件”，然后显示“Gstreamer 错误”（连续两次），但大多数情况下，它可以打开所有视频格式。它检测到视频的存在（mp4、mkv、avi 格式），但无法播放视频。我尝试了不同的权限组合以排除该问题。我还使用以下命令更新了 Gstreamer：
sudo apt install libdvdnav4 libdvdread4 gstreamer1.0-plugins-bad gstreamer1.0-plugins-ugly libdvd-pkg
sudo dpkg-reconfigure libdvd-pkgsudo
apt install ubuntu-restricted-extras
[编辑：输出dpkg -l | grep gstreamer]
$ dpkg -l | grep gstreamer
ii gir1.2-gstreamer-1.0:amd64 1.14.5-0ubuntu1~18.04.1 amd64 GObject introspection data for the GStreamer library
ii gstreamer1.0-alsa:amd64 1.14.5-0ubuntu1~18.04.1 amd64 GStreamer plugin for ALSA
ii gstreamer1.0-clutter-3.0:amd64 3.0.26-1 amd64 Clutter PLugin for GStreamer 1.0
ii gstreamer1.0-fluendo-mp3:amd64 0.10.32.debian-1 amd64 Fluendo mp3 decoder GStreamer 1.0 plugin
ii gstreamer1.0-gl:amd64 1.14.5-0ubuntu1~18.04.1 amd64 GStreamer plugins for GL
ii gstreamer1.0-gtk3:amd64 1.14.5-0ubuntu1~18.04.1 amd64 GStreamer plugin for GTK+3
ii gstreamer1.0-libav:amd64 1.14.5-0ubuntu1~18.04.1 amd64 libav plugin for GStreamer
ii gstreamer1.0-packagekit 1.1.9-1ubuntu2.18.04.5 amd64 GStreamer plugin to install codecs using PackageKit
ii gstreamer1.0-plugins-bad:amd64 1.14.5-0ubuntu1~18.04.1 amd64 GStreamer plugins from the "bad" set
ii gstreamer1.0-plugins-base:amd64 1.14.5-0ubuntu1~18.04.1 amd64 GStreamer plugins from the "base" set
ii gstreamer1.0-plugins-base-apps 1.14.5-0ubuntu1~18.04.1 amd64 GStreamer helper programs from the "base" set
ii gstreamer1.0-plugins-good:amd64 1.14.5-0ubuntu1~18.04.1 amd64 GStreamer plugins from the "good" set
ii gstreamer1.0-plugins-ugly:amd64 1.14.5-0ubuntu1~18.04.1 amd64 GStreamer plugins from the "ugly" set
ii gstreamer1.0-pulseaudio:amd64 1.14.5-0ubuntu1~18.04.1 amd64 GStreamer plugin for PulseAudio
ii gstreamer1.0-tools 1.14.5-0ubuntu1~18.04.1 amd64 Tools for use with GStreamer
ii gstreamer1.0-vaapi:amd64 1.14.5-0ubuntu1~ubuntu18.04.1 amd64 VA-API plugins for GStreamer
ii gstreamer1.0-x:amd64 1.14.5-0ubuntu1~18.04.1 amd64 GStreamer plugins for X11 and Pango
ii libgstreamer-gl1.0-0:amd64 1.14.5-0ubuntu1~18.04.1 amd64 GStreamer GL libraries
ii libgstreamer-plugins-bad1.0-0:amd64 1.14.5-0ubuntu1~18.04.1 amd64 GStreamer libraries from the "bad" set
ii libgstreamer-plugins-base1.0-0:amd64 1.14.5-0ubuntu1~18.04.1 amd64 GStreamer libraries from the "base" set
ii libgstreamer-plugins-good1.0-0:amd64 1.14.5-0ubuntu1~18.04.1 amd64 GStreamer development files for libraries from the "good" set
ii libgstreamer1.0-0:amd64 1.14.5-0ubuntu1~18.04.1 amd64 Core GStreamer libraries and elements
ii libreoffice-avmedia-backend-gstreamer 1:6.0.7-0ubuntu0.18.04.10 amd64 GStreamer backend for LibreOffice
为什么当其他视频播放器（VLC、TOTEM、MPV 等）都在工作时，Gnome-Subtitles 却无法打开某些视频？这是否与文件本身有关？