Lip synchronization in a video conference

1. A method of synchronizing a plurality of data streams having time-stamped packets, wherein the plurality of data streams are of a first type and at least a second type different than the first type, of which at least one stream of the first type is to be processed at a server, the method comprising:

re-dating a timestamp of a packet, using a processor, based on an estimated relative delay for transport up to the server between first-type and second-type streams and a predicted relative delay representative of a processing duration difference between first-type and second-type streams, thereby allowing the relative delays to cancel at least partially.

2. The method of claim 1 , further comprising:

processing the at least one stream of the first type to obtain at least one processed stream of time-stamped data packets,

wherein at least one of a data packet in the at least one processed stream or a data packet in a second-type stream is re-dated.

3. The method of claim 2 , wherein the at least one stream of the first type includes two first-type streams and wherein the two first-type streams are processed to obtain the at least one processed stream of time-stamped data packets.

4. The method of claim 1 , further comprising:

relaying packets of the first-type and second-type streams independently of one another.

5. The method of claim 1 , wherein the relative transport delay is estimated as a difference between a first period, elapsed from a timestamp of a packet in a first-type stream to a receipt time of this packet, and a second period, elapsed from a timestamp of a packet in a second-type stream to a receipt time of this packet.

6. The method of claim 1 , wherein:

the streams are ordered in synchronous pairs, each pair includes a first-type stream and a second-type stream;

first-type streams are to be processed to obtain a processed stream; and

timestamps in packets of each second-type stream are re-dated, to preserve synchronicity of the stream and a contribution to the processed stream made by the first-type stream of the pair, and these packets are relayed.

7. The method of claim 1 , wherein the first type is audio and the second type is video, and wherein streams of the first type are to be processed by combination.

8. The method of claim 1 , wherein each stream includes a sub-stream of data packets and an accompanying sub-stream of control packets including timestamps associating a point in the sub-stream of data packets with a point in time, wherein re-dating the timestamp of a packet comprises:

re-dating a timestamp of a control packet.

9. The method of claim 8 , wherein:

the first-type streams are processed to generate a processed stream including a sub-stream of data packets and a sub-stream of control packets, each control packet carrying a timestamp associating a point in the sub-stream of data packets with a point in reference time at which this point in the sub-stream of data packets was obtained by processing; and

the re-dating includes setting a timestamp of a control packet accompanying a second-type stream to the sum of a current reference time, the relative processing delay and the relative transport delay between first-type and second-type streams.

10. A apparatus for handling a plurality of data streams of time-stamped packets, comprising:

a first receiving means for receiving packets in streams of a first type to be processed;

a second receiving means for receiving packets in streams of a second type different than the first type; and

a relaying means for re-dating timestamps of packets in streams of at least one of the first and second types, on the basis of a predicted relative delay representative of processing time duration difference between first-type and second-type streams and an estimated relative delay for transport up to the apparatus between first-type and second-type streams, thereby allowing the relative delays to cancel at least partially.

11. The apparatus of claim 10 , further comprising:

a processing means for inputting at least one stream of the first type and for outputting a processed stream,

wherein the relaying means is configured to relay packets in streams of the one type after completion of re-dating.

12. The apparatus of claim 10 , wherein:

the first and second receiving means record receipt times of control packets; and

the relaying means estimates the relative transport delay as a difference between a first period, elapsed from a timestamp to a receipt time of a packet in a first-type stream, and a second period, elapsed from a timestamp to a receipt time of a packet in a second-type stream.

13. The apparatus of claim 10 , wherein the apparatus is configured to handle synchronous pairs of streams, each synchronous pair of streams including a first-type stream and a second-type stream, wherein:

the processing means processes first-type streams to obtain a processed stream; and

the relaying means re-dates timestamps in packets of each second-type stream, to preserve synchronicity of the stream and a contribution to the processed stream made by the first-type stream of the pair, and to relay packets with re-dated timestamps.

14. The apparatus of claim 13 , wherein the apparatus is configured to handle streams each including a sub-stream of data packets and an accompanying sub-stream of control packets including timestamps each associating a point in the sub-stream of data packets with a point in time,

wherein the relaying means re-dates timestamps of control packets.

15. An apparatus for enabling synchronization of a plurality of data streams having time-stamped packets, wherein the plurality of data streams are of a first type and at least a second type different than the first type, of which at least one stream of the first type is due to be processed at a server, the apparatus comprising:

a memory; and

a processor configured to execute instructions stored in the memory to:

re-date a timestamp of a packet based on an estimated relative delay for transport up to the server between first-type and second-type streams and a predicted relative delay representative of a processing time difference between first-type and second-type streams.

16. The apparatus of claim 15 , wherein the processor is further configured to:

process the at least one stream of the first type to obtain at least one processed stream of time-stamped data packets,

wherein at least one of a data packet in the at least one processed stream or a data packet in a second-type stream is re-dated.

17. The apparatus of claim 16 , wherein the at least one stream of the first type includes two first-type streams and wherein the two first-type streams are processed to obtain the at least one processed stream of time-stamped data packets.

18. The apparatus of claim 15 , wherein the processor is further configured to:

relay packets of the first-type and second-type streams independently of one another.

19. The apparatus of claim 15 , wherein the relative transport delay is estimated as a difference between a first period, elapsed from a timestamp of a packet in a first-type stream to a receipt time of this packet, and a second period, elapsed from a timestamp of a packet in a second-type stream to a receipt time of this packet.

20. The apparatus of claim 15 , wherein:

the streams are ordered in synchronous pairs, each pair includes a first-type stream and a second-type stream;

first-type streams are due to be processed to obtain a processed stream; and

timestamps in packets of each second-type stream are re-dated, to preserve synchronicity of the stream and a contribution to the processed stream made by the first-type stream of the pair, and these packets are relayed.