A method of transmitting user input data from a wireless sink device to a wireless source device, over a wireless User Input Back Channel, UIBC, the method comprising: transmitting, by the wireless sink device, a first real-time streaming protocol, RTSP, message to the wireless source device, wherein the RTSP message identifies a first list of input categories supported by the wireless sink device and a plurality of first lists of supported types, wherein each of the supported input categories of the first list of supported input categories has an associated first list of supported types; receiving, at the wireless sink device, a second RTSP message from the wireless source device, wherein the second RTSP message identifies a second list of supported input categories supported by the wireless source device and a plurality of second lists of supported types, wherein each of the supported input categories of the second list of supported input categories has an associated second list of supported types, wherein the second list is a subset of the first list; transmitting, by the wireless sink device, a message confirming that the types of the second list are enabled; obtaining, at the wireless sink device, user input data, wherein the input user data is for controlling content that is being transmitted from the wireless source device to the wireless sink device; generating, at the wireless sink device, a data packet header, wherein the data packet header comprises a field to identify the enabled input category of the user input data, wherein the input category identifies how payload data is formatted; generating, at the wireless sink device, a data packet comprising the data packet header and the payload data; transmitting, from the wireless sink device, the data packet to the wireless source device; and receiving content from the wireless source device based on the user input data within the data packet. transmitting, by the wireless sink device, a first real-time streaming protocol, RTSP, message to the wireless source device, wherein the RTSP message identifies a first list of input categories supported by the wireless sink device and a plurality of first lists of supported types, wherein each of the supported input categories of the first list of supported input categories has an associated first list of supported types; receiving, at the wireless sink device, a second RTSP message from the wireless source device, wherein the second RTSP message identifies a second list of supported input categories supported by the wireless source device and a plurality of second lists of supported types, wherein each of the supported input categories of the second list of supported input categories has an associated second list of supported types, wherein the second list is a subset of the first list; transmitting, by the wireless sink device, a message confirming that the types of the second list are enabled; obtaining, at the wireless sink device, user input data, wherein the input user data is for controlling content that is being transmitted from the wireless source device to the wireless sink device; generating, at the wireless sink device, a data packet header, wherein the data packet header comprises a field to identify the enabled input category of the user input data, wherein the input category identifies how payload data is formatted; generating, at the wireless sink device, a data packet comprising the data packet header and the payload data; transmitting, from the wireless sink device, the data packet to the wireless source device; and receiving content from the wireless source device based on the user input data within the data packet.