In-band quality data

1. A method of transmitting data in a media stream to a receiving device, the media stream being in accordance with a media streaming protocol which defines a data structure comprising a type identifier field for specifying a type of data contained within the data structure, wherein the type identifier field is settable to a first type identifier or a second type identifier different from the first type identifier, the method comprising:

determining whether or not the receiving device is capable of processing data in a data structure having the type identifier field set to the second type identifier, wherein if it is determined that the receiving device is capable of processing data in a data structure having the type identifier field set to the second type identifier, the method further comprising:

generating data of a first type, the first type being associated with the first type identifier in accordance with said protocol;

encapsulating the generated data in a data structure defined by said protocol;

setting the type identifier field of the data structure to the second type identifier;

forming a packet comprising the data structure; and

transmitting the packet in the media stream.

2. A method as claimed in claim 1 , wherein the generated data is quality data.

3. A method as claimed in claim 2 , wherein the generated data comprises one or more of: FEC data; feed-forward data; feedback data; retransmission data; and configuration parameters.

4. A method as claimed in claim 1 , wherein the method further comprises: receiving a prior packet comprising a data structure having the second type identifier, wherein the data is generated in dependence on the received prior packet.

5. A method as claimed in claim 1 , wherein the method further comprises:

receiving a device identifier from a receiving device; and

determining a mode of operation of the receiving device in dependence on the received device identifier, wherein the type identifier is set in dependence on the determined mode of operation.

6. A method as claimed in claim 1 , wherein the method further comprises receiving the transmitted packet at a receiving device, wherein:

if the receiving device is operating in a first mode, the receiving device analyses the encapsulated data in dependence on the second type identifier; and

if the receiving device is operating in a second mode, the receiving device discards the packet in dependence on second type identifier.

7. A method as claimed in claim 1 , wherein the second type identifier is unspecified in the protocol.

8. A method as claimed in claim 1 , wherein the media streaming protocol is in accordance with a RTP Payload Format for H.264 Video standard.

9. A method as claimed in claim 8 , wherein the second type identifier is a Network Abstraction Layer (NAL) unit type field having a NAL unit type value of 0, 30 or 31.

10. A method as claimed in claim 8 , wherein the generated data comprises supplemental enhancement information, as defined in the protocol.

11. A method as claimed in claim 1 , wherein if it is determined that the receiving device is not capable of processing data in a data structure having the type identifier field set to the second type identifier, the transmission of quality data is disabled.

12. A data processing device configured to transmit data in a media stream to a receiving device, the media stream being in accordance with a media streaming protocol which defines a data structure comprising a type identifier field for specifying a type of data contained within the data structure, wherein the type identifier field is settable to a first type identifier or a second type identifier different from the first type identifier, the device comprising a controller, an encapsulator, a packetiser and a transceiver, wherein:

the data processing device is configured to determine whether or not the receiving device is capable of processing data in a data structure having a type identifier set to the second type identifier;

wherein if it is determined that the receiving device is capable of processing data in a data structure having the type identifier set to the second type identifier:

the controller generates data of a first type, the first type being associated with the first type identifier in accordance with said protocol,

the encapsulator:

encapsulates the generated data in a data structure defined by the protocol, and

sets the type identifier field to the second type identifier;

the packetiser forms a packet comprising the data structure; and

the transceiver transmits the packet in the media stream.

13. A device as claimed in claim 12 , wherein the data of the first type is quality data.

14. A device as claimed in claim 13 , wherein the data of the first type comprises one or more of: FEC data; feed-forward data; feedback data; retransmission data; and configuration parameters.

15. A device as claimed in claim 12 , wherein the second type identifier is not associated with the first type of data in the protocol.

16. A device as claimed in claim 12 , wherein the second type identifier is unspecified in the protocol.

17. A device as claimed in claim 12 , wherein the media streaming protocol is in accordance with a RTP Payload Format for H.264 Video standard.

18. A device as claimed in claim 17 , wherein the second type identifier is a Network Abstraction Layer (NAL) unit type field having a NAL unit type value of 0, 30 or 31.

19. A device as claimed in claim 17 , wherein the generated data comprises supplemental enhancement information, as defined in the protocol.

20. A device as claimed in claim 12 , wherein if it is determined that the receiving device is not capable of processing data in a data structure having the type identifier field set to the second type identifier, the transmission of is quality data is disabled.

21. A device as claimed in claim 12 , wherein the receiving device comprises a transceiver, the transceiver being configured to transmit a packet to the data processing device, the transmitted packet being capable of indicating whether or not the data processing device is capable of processing data in a data structure having the type identifier set to the second type identifier.

22. A device as claimed in claim 21 , wherein the transceiver is further configured to receive a prior packet comprising a data structure having the second type identifier, wherein the data is generated in dependence on the received prior packet.