A method of operating a video/audio processing apparatus is suggested. The system comprises a plurality of processing units connected by data links for communicating packetized data. The method comprises the following steps: receiving the input signals according to user requests; providing resources for processing, routing, and transmitting signals; providing input signals; routing the input signals to selectable destinations according to user requests; monitoring the required resources for processing and/or routing the signals; comparing the required resources with available resources; and issuing a warning message to the user if the required resources exceed the available resources of the system. Also a processing apparatus is suggested which is adapted for executing the method.