Synchronization watermarking in multimedia streams
Synchronization of related packet data network streams is provided. Synchronization is achieved by inserting synchronization packets into data streams that are to be aligned with one another after transmission of those data streams across a network. More particularly, corresponding synchronization packets are inserted into the corresponding data streams at the same time, to serve as markers for performing synchronization of the data at the receiving end. The corresponding data streams may comprise an audio data stream and a corresponding video data stream.
1. A method for synchronizing packet data streams, comprising:
generating a first synchronization packet, wherein said first synchronization packet has a payload that includes a synchronization flag;
inserting said first synchronization packet in a first data stream;
generating a second synchronization packet, wherein said second synchronization packet has a payload that includes a synchronization flag, and wherein said second synchronization packet corresponds to said first synchronization packet;
inserting said second synchronization packet in a second data stream, wherein said first and second data streams are related to one another,
wherein said generating first and second synchronization packets and inserting said first and second synchronization packets in first and second data streams respectively is performed at a first network entity;
at a second network entity:
generating a third synchronization packet, wherein said third synchronization packet has a payload that includes a synchronization flag;
inserting said third synchronization packet in a third data stream;
generating a fourth synchronization packet, wherein said fourth synchronization packet has a payload that includes a synchronization flag; and
wherein said fourth synchronization packet corresponds to said third synchronization packet;
inserting said fourth synchronization packet in a fourth data stream;
at a third network entity:
receiving said first, second, third and fourth data streams;
detecting in said first data stream said first synchronization packet;
detecting in said second data stream said second synchronization packet;
determining that said first and second synchronization packets correspond to one another;
aligning packets included in said first data stream in a vicinity of said first synchronization packet with packets included in said second data stream in a vicinity of said second synchronization packet;
detecting in said third data stream said third synchronization packet;
detecting in said fourth data stream said fourth synchronization packet;
determining that said third and fourth synchronization packets correspond to one another;
aligning packets included in said third data stream in a vicinity of said third synchronization packet with packets included in said fourth data stream in a vicinity of said fourth synchronization packet.
2. The method of claim 1 , further comprising:
receiving said first and second data streams at the second network entity;
detecting in said first data stream said first synchronization packet;
detecting in said second data stream said second synchronization packet;
determining that said first and second synchronization packets correspond to one another;
aligning packets included in said first data stream in a vicinity of said first synchronization packet with packets included in said second data stream in a vicinity of said second synchronization packet.
3. The method of claim 1 , wherein a synchronization packet is inserted in said first data stream periodically, and wherein a synchronization packet is inserted in said second data stream periodically.
4. The method of claim 1 , wherein said payload of said first and second synchronization packets includes a reference value.
5. The method of claim 4 , wherein said reference value in said first synchronization packet is within a first predetermined range of said reference value in said second synchronization packet.
6. The method of claim 4 , wherein said reference value in said first synchronization packet is the same as the reference value in said second synchronization packet.
7. The method of claim 4 , wherein said reference value comprises a clock value.
8. The method of claim 4 , wherein said reference value comprises a count value.
9. The method of claim 1 , wherein the first synchronization packet includes a header, said header of a first type includes a Real Time Protocol header.
10. The method of claim 1 , wherein said synchronization flag has good correlation properties.
11. The method of claim 1 , wherein a vicinity of a synchronization packet is one of: between said synchronization packet and a previous synchronization packet; between said synchronization packet and a next synchronization packet; and within a predetermined number of packets of said synchronization packet.
12. The method of claim 2 , further comprising:
presenting a first audio output and a first video output generated from said aligned packets included in said first and second data streams to a user at a communication endpoint.
13. The method of claim 1 , wherein said first synchronization packet is inserted in said first data stream at a first time, wherein said second synchronization packet is inserted in said second data stream at a second time, and wherein said first time is within a predetermined amount of said second time.
14. The method of claim 1 , wherein said first synchronization packet is inserted in said first data stream at a first time, wherein said second synchronization packet is inserted in said second data stream at a second time, and wherein said first time is within 100 milliseconds of said second time.
15. The method of claim 1 , wherein said second synchronization packet is inserted into said second data stream after a video frame boundary.
16. The method of claim 1 , wherein said first synchronization packet is inserted in said first data stream when silence is detected in that data stream.