# Physical routing

> How sources, destinations, ports and bundles form a physical route, and how display labels and label strategy fallback work.

Physical routing connects an individual source port to an individual destination port. Buttons can also present related ports as bundles, so one operational choice represents signals that belong together, like an SDI mux of one video signal, 16 audio signals and one ancillary signal. This page explains the physical routing model used by connections such as an ATEM or video router. Virtual routing and tielines build on this model but are outside this page's scope. Start with a source and destination A source provides a signal. A camera input, playback output, or router input can appear as a source in Buttons. A destination receives a signal. A switcher program bus, auxiliary output, monitor feed, or router output can appear as a destination. A route maps a source to a destination: Camera 1 → Program source destination The source and destination directions describe their role in the route, not necessarily the label printed beside a connector on the device. Ports are the routable endpoints A port is one routable endpoint. Buttons routes a source port to a compatible destination port. For an ATEM connection, Camera 1 Video can be a source port and Program Video can be a destination port. The route between them changes one video path. Ports are the physical routing model's smallest selectable endpoints. Each port belongs to a connection or another routing provider and carries the information Buttons needs to identify and operate it. Bundles keep related ports together A bundle groups ports that represent one operational source or destination. For example, an ATEM connection exposes these resources: Camera 1 source bundle ├── Video port ├── Audio 1/2 port └── Audio 3/4 port Program destination bundle ├── Video port ├── Audio 1/2 port └── Audio 3/4 port Routing Camera 1 to Program at the bundle level can request routes for the compatible ports inside both bundles. Routing only Camera 1 Video changes the video port without implying that its audio ports also change. This distinction matters when inspecting routing state or diagnosing a partial result: the bundle is the operational grouping, while its ports are the endpoints that are actually routed. Connections supply physical routing resources Router-aware connections supply their available source ports, destination ports, bundles, labels, and routing behavior to Buttons. The resources depend on the connected product and the options enabled for that connection. For example, an ATEM connection can expose inputs as sources and program buses, preview buses, auxiliary outputs, multiviewer windows, or audio destinations as destinations. Disabling one of those routing areas in the connection configuration removes it from the resources the connection supplies. Choose which label to display A connection can supply two labels for a port or bundle: Name is the stable name of the resource. For an ATEM input, this could be Input 1 . Ext Custom Label is the user-defined label received from the connected device. For the same ATEM input, this could be Cam 1 . It can change when someone renames the input on the ATEM itself. Buttons also provides User , Setup , and Installation labels that can be maintained in Buttons. These do not replace Name or Ext Custom Label ; they are additional display choices. Each place that displays a port or bundle can choose its label source. For example, the Routing UI can display one label type while a Router Section or Custom Router uses another. How Label Strategy fallback works The selected Display Label is always the first choice. Label Strategy controls what Buttons tries when that label has no value. The arrows show the fallback order. Buttons starts at the selected label's position and moves to the right until it finds a value. It does not use labels shown to the left of the selected label. For example, with this strategy: User → Setup → Installation → Ext Custom Label → Name If User is selected, Buttons tries User , Setup , Installation , Ext Custom Label , then Name . If Setup is selected, Buttons tries Setup , Installation , Ext Custom Label , then Name . It does not fall back to User . If Ext Custom Label is selected, Buttons tries Ext Custom Label , then Name . If Name is selected, there is no further fallback. The available strategies are: Strategy Intended use User → Setup → Installation → Ext Custom Label → Name Prefer labels maintained in Buttons, then labels supplied by the device. This is the default order. Ext Custom Label → User → Setup → Installation → Name Prefer the device's current custom label before labels maintained in Buttons. User → Setup → Installation → Name Ignore Ext Custom Label as a fallback. If Ext Custom Label itself is the selected display label, it can still be displayed when it has a value. Off Use only the selected display label. If it has no value, display no label. A fallback uses the first non-empty label it finds. If the ATEM's Ext Custom Label changes, any routing interface currently resolving to that label displays the updated value. Tip Choose labels for the people using each routing interface. A Router Section for operators might display User , while an engineering view uses Name or Ext Custom Label to compare Buttons with the connected device. Current state comes from the controlled system Buttons tracks the active source reported for a destination. After a route is requested, the resulting state shows which source the controlled system reports as active. The request and the reported state are different information. A request can fail, be blocked, or affect only some ports in a bundle. Treat the active source shown for each destination port as the routing state, and use the route result or report to investigate any mismatch. How the concepts fit together Concept What it represents ATEM example Source The sending side of a route Camera 1 Destination The receiving side of a route Program Port One routable endpoint Camera 1 Video Bundle Related ports presented as one source or destination bundle Camera 1 containing Video, Audio 1/2 and Audio 3/4 ports These concepts describe physical routing resources. A virtual route may later refer to higher-level objects, but it must ultimately resolve to routable endpoints such as these. Where to go next Learn how to select bundles and take a route .