codecs: Virtual functions should return GstFlowReturn, not boolean value
The return type of most virtual functions (except for
output_picture) are boolean, not
GstFlowReturn which looks bad design because baseclass doesn't understand why subclass returned
false. Then baseclass will return
GST_FLOW_ERROR whatever the reason was.
I'd suggest updating all virtual functions so that all of them can return
GstFlowReturn, as all methods will be called in