GStreamer : Pad

- GStreamer : Pad -

Pads are element's input and output, where you can connect other element. They are used to negotiate links and data flow between elements in GStreamer. a pad can be viewed as a "plug" or "port" on an element where links may be made with other element, and though which data can flow to or from those elements. Pads have specific data handling capabilities: a pad can restrict the type of data that flows through it. Links are only allowed between two pad when the allowed data types of the two pads are compatible. Data type are negotiated between pads using a process called cap negotiation. Data types are described as a GstCaps.

An analogy may be helpful here. A pad is similar to a plug or jack on a physical device. Consider, for example. a home theater system consisting of an amplifier, a DVD player, and a (silent) video projector. Linking the DVD player to the amplifier is allowed because both devices have audio jacks, and linking the projector to the DVD player is allowed because both devices have compatible video jacks. Links between the projector and the amplifier may not be made because the projector and amplifier have different types of jacks. Pads in GStreamer serve the same purpose as the jacks in the home theater system.

For the most part, all data in GStreamer flows one way through a link between elements. Data flows out of one element through one or more source pads, and elements accept incoming data through one or more sink pad,  Source and sink elements have only source and sink  pads, respectively. Data usually mean buffers(described by the GstBuffer).

- Refer to GStreamer Application Guide -