Milestone synchronization in broadcast multimedia streams

• US 20060242240A1
• Filed: 03/28/2005
• Published: 10/26/2006
• Est. Priority Date: 03/28/2005
• Status: Active Grant

• Current Assignee: WSOU Investments, LLC (WSOU Holdings, LLC)
• Original Assignee: Alcatel-Lucent SA (Nokia Corporation)
• Inventors: Parker, Alistair John, Dion, Gino Louis, Boven, Christian Van, Higgins, Sean Gordon, Furlong, Jeff, Bettelheim, Richard
• Granted Patent: US 7,668,914 B2
• Time in Patent Office: Days
• US Class Current: 709/205
• CPC Class Codes: H04N 21/23406 involving management of server-side video buffer
• CPC Class Codes: H04N 21/2362 Generation or processing of Service Information [SI]
• CPC Class Codes: H04N 21/4384 involving operations to reduce the access time, e.g. fast-tuning for reducing channel switching latency
• CPC Class Codes: H04N 21/6405 Multicasting data broadcast and multicast in packet switching networks H04L12/18
• CPC Class Codes: H04N 21/6408 Unicasting
• CPC Class Codes: H04N 21/6581 Reference data, e.g. a movie identifier for ordering a movie or a product identifier in a home shopping application
• CPC Class Codes: H04N 21/8455 involving pointers to the content, e.g. pointers to the I-frames of the video stream
• CPC Class Codes: H04N 7/17318 Direct or substantially direct transmission and handling of requests

Abstract

A server at the edge of a broadband network distributes multimedia content streams to clients, while ensuring that the first data delivered to each client is key data (milestones) needed for correctly decoding the stream content. This is obtained by buffering the packets in the incoming stream and transmitting the packets from the buffer in an outgoing stream, starting with the most recent milestone placed in the buffer before a request to join the respective incoming stream is received. As the writing to and reading from the buffer are performed at different rates, the incoming and outgoing streams are eventually synchronized, at which point the client may be switched to receive the incoming stream directly.

Claims

1. In a broadcast system for delivering entertainment content to receivers over multimedia content streams, each stream characterized in that stream rendering cannot commence until a milestone data structure has been received, a server comprising:

a listening mechanism for detecting a request indicating that a client wishes to receive a specified multimedia content stream carrying content of interest;

a synchronization unit for streaming to the client an outgoing stream with the content of interest, starting with a most recent milestone data structure in the specified multimedia content stream with respect to the request receipt time from the time of request until the outgoing stream is synchronized with the specified multimedia content stream; and

a multicast feed for receiving all said multimedia content streams from a head-end over a broadband network and distributing each stream to a respective client once the outgoing stream is synchronized with the specified multimedia content stream,

wherein the most recent milestone data structure enables the client to immediately decode the content of interest from the outgoing stream.

2. The server of claim 1, wherein the milestone data structure comprises program guide and system information (PSI) and a packet marking the beginning of a full picture data structure.

3. The sever of claim 1, wherein the synchronization unit comprises:

a circular buffer;

a finder for detecting all milestone data structures in the specified multimedia content stream;

a receiver for placing the packets from the specified multimedia content stream at the end of the buffer as they arrive, and keeping track of the position of the milestone data structures in the buffer;

a sender for creating a marker in the buffer at the most recent milestone data structure relative to the time of arrival of the request and for sending each next content packet from the position indicated by the marker,

wherein the receiver places the packets in the buffer at a first rate and increments the marker at a second rate, higher than the first rate, until the marker position catches-up with the position of the last packet placed in the buffer.

4. The server of claim 3, further comprising a PSI (program guide and system information) controller for detecting program and system information in the specified multimedia content stream and sending same to the client in response to the request, before any content packets are sent to the client.

5. The server of claim 3, wherein, for a MPEG stream, the milestone data structure is an I-frame.

6. The server of claim 2, wherein the buffer size is adjusted according to the rate and size of the milestone data structure in the specified multimedia content stream.

7. The server of claim 3, wherein, for a MPEG2 transport stream, the buffer size is larger than the largest conceivable group of pictures (GOP) in the specified multimedia content stream.

8. The sever of claim 3, wherein the buffer size is matched to the packet size.

9. The server of claim 3, wherein said synchronization unit further comprises means for reducing the bandwidth in the outgoing stream by discarding packets unnecessary for stream play-out.

10. The server of claim 9, wherein, for a MPEG2 transport stream, said means for reducing the bandwidth comprises a filter for discarding NULL packets and PAT/PMT packets received while the client plays-out the outgoing stream.

11. The server of claim 3, wherein whenever one client lodged a request for the specified multimedia content stream, the outgoing stream is unicast to the client, and whenever two or more clients request to join the same specified multimedia content stream, the clients are assigned to the same marker, and the outgoing stream is multicast to these clients.

12. The server of claim 3, wherein the synchronization unit further comprises a buffer for copying a certain number of content packets from the specified multimedia content stream, for enabling instant-replay functionality.

13. The server of claim 3, provided at the edge of the broadband network, for serving a plurality of clients over a local network.

15. The server of claim 3, wherein said listening mechanism is an IGMP snoop.

14. The server of claim 14, provided at the edge of the broadband network within any of a digital subscriber line access multiplexer (DSLAM) and a network device already present close to the edge.

16. In a broadcast system for delivering entertainment content to clients over multimedia content streams, each stream characterized in that stream rendering cannot commence until a milestone data structure has been received, a synchronization unit comprising:

a circular buffer;

a finder for detecting all milestone data structures in the specified multimedia content stream;

a receiver for placing the packets from the specified multimedia content stream at the end of the buffer as they arrive, and keeping track of the position of the milestone data structures in the buffer;

a sender for creating a marker in the buffer at the most recent milestone data structure relative to the time of arrival of the request, and for sending each next content packet from the position indicated by the marker,

wherein the receiver places the packets in the buffer at a first rate and increments the marker at a second rate, higher than the first rate, until the marker position catches-up with the position of the last packet placed in the buffer.

17. The synchronization unit of claim 16, wherein further comprising means for reducing the bandwidth between in the outgoing stream by discarding packets unnecessary for stream play-out.

18. The synchronization unit of claim 17, implemented in a server at the edge of said broadband network.

19. The synchronization unit of claim 17, implemented in a head-end at for reducing the bandwidth of said specified multimedia content stream over said broadband network by discarding packets unnecessary for stream play-out.

20. A method for delivering entertainment content to receivers over multimedia content streams, each stream characterized in that stream rendering cannot commence until a milestone data structure has been received, comprising:

a) listening for a request indicating that a client wishes to receive a specified multimedia content stream carrying content of interest;

b) streaming to the client the content of interest in an outgoing stream, starting with a most recent milestone data structure in the specified multimedia content stream with respect to the request receipt time;

c) synchronizing the outgoing stream with the specified multimedia content stream; and

d) switching the client form receiving the outgoing stream to receive the specified multimedia content stream once the streams are synchronized.

21. The method of claim 20, wherein step b) comprises:

providing a delayed version of the specified multimedia content stream in a circular buffer;

detecting all milestone data structures in the specified multimedia content stream;

placing the packets from the specified multimedia content stream at the end of the buffer as they arrive at a first rate, while keeping track of the position of the milestone data structures in the buffer;

creating a marker in the buffer at the most recent milestone data structure relative to the time of arrival of the request, and sending each next content packet from the position indicated by the marker,

incrementing the marker at a second rate, higher than the first rate, until the marker position catches-up with the position of the last packet placed in the buffer.