The parseCa function was corrected with the lookup file GtkD uses:
https://github.com/gtkd-developers/GtkD/blob/master/src/APILookupGstMpegts.txt#L33

Aha, so you have a manual correction system. This now all makes sense.

Can I get you to write bug reports to GStreamer for all the GIR failures you found with GStreamer – to back up the fact that GStreamer source is not properly annotated. Sebastian will then mentor me to fix the GStreamer C source so as to create GIR files that do not need manual intervention. This should make life easier for D and Rust bindings to GStreamer.

https://gstreamer.freedesktop.org/bugs/