Optimized transmission of text sample format description for streaming timed text

A streaming server transmitting formatted text to a client via a communication system using a Real-time Transport Protocol (RTP), wherein the formatted text comprises a plurality of text samples that are associated with at least one text sample format description, and wherein the at least one text sample format description is signaled in-band to the client, the streaming server comprising:

• a packet forming unit operable to form at least one data packet to be transmitted to the client during a given communication session,
• a processing unit operable to determine whether a text sample format description for a particular text sample to be added to the at least one data packet is already included in the at least one data packet for another text sample within the at least one data packet;
• and
• a transmission unit operable to transmit the at least one data packet to the client, wherein:
• the packet forming unit is operable to add said particular text sample to the at least one data packet without adding the text sample format description for said particular text sample, if the processing unit has determined that the text sample format description for said particular text sample is already included in the at least one data packet,
• the processing unit is further operable to determine whether the text sample format description for said particular text sample has already been provided to the client for another earlier text sample in a previously transmitted data packet during the given communication session, if the text sample format description for said particular text sample to be added to the at least one data packet is not already included in the at least one data packet, and
• the packet forming unit is further operable to add the particular text sample to be transmitted to the at least one data packet to be transmitted without adding the text sample format description for said particular text sample, if the processing unit has determined that the text sample format description for said particular text sample has already been provided for an earlier text sample in the previously transmitted data packet during the given communication session, and to add said particular text sample and its text sample format description to the at least one data packet, if the processing unit has determined that the text sample format description for said particular text sample is not already included in said at least one data packet for another text sample within the at least one data packet and has not already been provided for an earlier text sample in the previously transmitted data packet during the given communication session.

A method for operating a client in a communication system to receive formatted text from a streaming server using a Real-time Transport Protocol (RIP), wherein the formatted text comprises a plurality of text samples associated with at least one text sample format description, the method being performed by the client and comprising:

• receiving a data packet from the streaming server during a given communication session, wherein the data packet comprises at least one text sample,
• determining for a particular text sample comprised in the data packet, whether the data packet further comprises an associated text sample format description for the particular text sample,
• if the received data packet comprises the associated text sample format description for the particular text sample, selecting the associated text sample format description within the received data packet for the particular text sample,
• if the received data packet does not comprise the text sample format description for the particular text sample, determining whether the text sample format description for the particular text sample within the received data packet has been included in a data packet received earlier during the given communication session,
• if the text sample format description for the particular text sample has been included in the data packet received earlier during the given communication session, selecting a text sample format description for the particular text sample from the data packet received earlier during the given communication session, and
• formatting the particular text sample using the selected text sample format description.

A client for receiving formatted text from a streaming server using a Real-time Transport Protocol (RTP), wherein the formatted text comprises a plurality of text samples associated with at least one text sample format description, the client comprising:

• a receiving unit operable to receive a data packet from the streaming server during a communication session, wherein the data packet comprises at least one text sample,
• a processing unit operable to determine for each particular text sample within the data packet, whether the data packet further comprises an associated text sample format description for the particular text sample within the received data packet, and
• a selection unit operable to select the associated text sample format description within the data packet for the particular text sample, if it is determined by the processing unit that the received data packet includes the associated text sample format description for the particular text sample, wherein:
• the processing unit is further operable to determine whether the associated text sample format description for the particular text sample has been included in a data packet received earlier at the client during the given communication session, if the received data packet does not include the associated text sample format description for the particular text sample,
• the selection unit is further operable to select a text sample format description for the particular text sample within the received data packet from text sample format descriptions already received at the client during the given communication session, if it is determined by the processing unit that the associated text sample format description for the particular text sample has been included in a data packet received earlier during the given communication session, and
• the client further comprises a text formatting unit operable to format the particular text sample using the selected text sample format description.