Complete an asynchronous start operation. When the subclass overrides the start method, it should call BaseSrc.startComplete when the start operation completes either from the same thread or from an asynchronous helper thread.
a GstFlowReturn
Complete an asynchronous start operation. When the subclass overrides the start method, it should call BaseSrc.startComplete when the start operation completes either from the same thread or from an asynchronous helper thread.