In gstomx_base_filter.c there is a separate output_thread that calls push_buffer() that in turn calls gst_pad_push(). The return value of gst_pad_push() is not taken, and _chain() function (almost) always returns GST_FLOW_OK.

Instead, the output_thread should save this GstFlowReturn value and _chain() should use it as a return value. This way the downstream _push() return value gets propagated upstream, e.g. when pipeline is set to NULL. Currently the parser element just keeps on pushing frames to decoder, since chain incorrectly returns GST_FLOW_OK even the gst_pad_push() has returned GST_FLOW_WRONG_STATE.