In GRC, I've set up a packet detector that is working using the Header Payload Demux block. Unexpectedly, however, it seems the payload output port does not go silent when no header is detected. It outputs zeros, which the file sink block I have connected to that port then stores.
I've attached a screenshot of my flowgraph. The top row generates the packets. The middle row adds zeros between packets, to give the header payload demux something to do. The third row detects the packets, strips the header and sends the payload out to a file sink.
I would like the payload output port to be quiet when no header is detected, or I would like a way to control what the file sink stores. Tagged File Sink is not what I'm looking for, because it creates a new file every time a tag is detected.