And the answer was found using a gstreamer plugin named gnonlin. This component includes several gstreamer elements including gnlfilesource
which can start the video at a specific position.
The following command loads a video file and a subtitle and starts playing at the position specified in media-start
(nanoseconds):
gst-launch filesrc location=/data/videos/tbbt_s05e01.srt ! subparse ! bot. gnlfilesource location=file:///data/videos/tbbt_s05e01.avi duration=10000000000000 media-start=100000000000 ! ffmpegcolorspace ! textoverlay name=bot valignment=bottom ! xvimagesink