There is no update from you for a period, assuming this is not an issue anymore. Hence we are closing this topic. If need further support, please open a new one. Thanks
You may construct the pipeline without source first, and wait for the input image to create the image and change the pipeline to PLAYING state.
The appsrc element can be used by applications to insert data into a GStreamer pipeline. appsrc (gstreamer.freedesktop.org)