Method and system for reducing latency in a multi-channel multicast streaming environment in content-delivery networks

• US 20080025304A1
• Filed: 07/31/2006
• Published: 01/31/2008
• Est. Priority Date: 07/31/2006
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Venkataswami, Balaji Venkat, Velrajan, Ganesan, Santhanam, Srinivasan
• Granted Patent: US 7,995,576 B2
• Time in Patent Office: Days
• US Class Current: 370/390
• CPC Class Codes: H04L 12/1881 with schedule organisation, e.g. priority, sequence management
• CPC Class Codes: H04N 21/238 Interfacing the downstream path of the transmission network, e.g. adapting the transmission rate of a video stream to network bandwidth; Processing of multiplex streams hybrid fiber coaxial [HFC] networks for downstream channel allocation for video distribution H04L12/2801; flow control in packet networks H04L47/10; real-time communication protocols in data switching networks H04L65/00; scheduling or organising the servicing of application requests H04L67/60
• 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 21/8549 Creating video summaries, e.g. movie trailer retrieval in video databases by using presentations in form of a video summary G06F16/739

Abstract

Methods, systems and apparatus for reducing apparent latency in content-delivery networks are provided. Sources multicast certain ‘preview multicast streams’ to multiple subscribers. These preview multicast streams provide pre-recorded content of multicast streams. When a subscriber switches to a desired multicast stream, pre-recorded content of the desired multicast stream is reconstructed from a preview multicast stream. Thereafter, the pre-recorded content is played during the setup of the new multicast distribution tree to minimize latency. Once the distribution tree is setup, live content of the desired multicast stream is made available to the subscriber.

Claims

1. A method for reducing latency in a multicast network, the method comprising:

generating a preview multicast stream from a plurality of multicast streams to provide pre-recorded content in a predefined frame format;

multicasting the generated preview multicast stream to one or more subscribers;

in response to a request to switch from one multicast stream to another of the plurality of multicast streams, playing the pre-recorded content;

setting up a multicast tree while playing the pre-recorded content; and

switching to the requested one of the plurality of multicast streams.

2. The method of claim 1, wherein the predefined frame format comprises interleaved frames of the at least two multicast streams.

3. The method of claim 1, wherein the pre-recorded content comprises content that was recorded during a selected recording-time period.

4. The method of claim 1, wherein the pre-recorded content is multicast repeatedly for a selected preview-time period.

5. The method of claim 1, wherein the multicast network runs Protocol-Independent Multicast-Sparse Mode (PIM-SM) protocol.

6. A method for reducing latency in a multicast network, the method comprising:

subscribing to a multicast steam;

receiving a preview multicast stream that provides pre-recorded content of a plurality of multicast streams;

reconstructing pre-recorded content of a multicast stream selected by a subscriber, from the received preview multicast stream; and

playing the reconstructed content.

7. The method of claim 6 further comprising switching to live content of the selected multicast stream when available.

8. The method of claim 6 further comprising caching the preview multicast stream.

9. The method of claim 6, wherein the preview multicast stream is subscribed automatically when the multicast stream is subscribed to by the subscriber.

10. The method of claim 6 further comprising pre-configuring the preview multicast stream.

11. In a system for reducing latency in a multicast network, a source adapted for providing a plurality of multicast streams, the source comprising:

means for generating a preview multicast stream from a multicast stream to provide pre-recorded content; and

means for multicasting the generated preview multicast stream when one of the plurality of multicast streams is selected, the multicasting of the preview multicast stream continuing until the selected multicast stream is available.

12. A system for reducing latency in a multicast network, the system comprising:

one or more sources adapted to generate one or more preview multicast streams from a plurality of multicast streams, each preview multicast stream providing pre-recorded content of two or more multicast streams in a predefined frame format.

13. The system of claim 12, wherein the one or more sources are further adapted to multicast the generated preview multicast streams.

14. The system of claim 12, wherein the predefined frame format comprises interleaved frames of the plurality of multicast streams.

15. The system of claim 12, wherein the pre-recorded content comprises content recorded during a predefined recording-time period and multicast for a predefined preview-time period.