Systems and Methods of Synchronizing Media Streams

• US 20080022320A1
• Filed: 06/30/2006
• Published: 01/24/2008
• Est. Priority Date: 06/30/2006
• Status: Abandoned Application

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Scientific-Atlanta Incorporated (Cisco Systems, Inc.)
• Inventors: Ver Steeg, William C.
• Application Number:
  US11/428,336
• Publication Number:
  US 20080022320A1
• Time in Patent Office: Days
• US Class Current: 725/78
• CPC Class Codes: H04N 21/2353 specifically adapted to content descriptors, e.g. coding, compressing or processing of metadata
• CPC Class Codes: H04N 21/4305 Synchronising client clock from received content stream, e.g. locking decoder clock with encoder clock, extraction of the PCR packets arrangements for synchronising receiver with transmitter by comparing receiver clock with transmitter clock H04L7/0012; arrangements for synchronising receiver with transmitter wherein the receiver takes measures against momentary loss of synchronisation H04L7/0083
• CPC Class Codes: H04N 21/43072 of multiple content streams on the same device
• 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 21/443 OS processes, e.g. booting an STB, implementing a Java virtual machine in an STB or power management in an STB

Abstract

Systems and methods are disclosed. One embodiment is a method of synchronizing media streams among a plurality of digital home communication terminals (DHCTs). The method comprises the steps of: decoding a stream of encoded media frames; receiving an indication of a desired playout time; determining a variation between the target playout time and the desired playout time; and adjusting the decoder playout speed to reduce the variation. At least a first portion of the frames have a target playout time conveyed in the stream. The indication of desired playout time is received for at least a second portion of the frames.

Claims

1. A method, performed in a digital home communication terminal (DHCT), of synchronizing media streams among a plurality of DHCTs, the method comprising the steps of:

decoding a stream of encoded media frames at a playout speed, at least a first portion of the frames having a target playout time conveyed in the stream;

receiving an indication of a desired playout time for at least a second portion of the frames;

determining a variation between the target playout time and the desired playout time; and

adjusting the decoder playout speed to reduce the variation.

2. The method of claim 1, wherein the indication of the desired playout time of a frame corresponds to the actual playout time of the corresponding frame in another one of the plurality of DHCTs.

3. The method of claim 1, wherein the adjusting step further comprises:

increasing the playout speed if the variation indicates that decoding in the DHCT lags behind decoding in another one of the plurality of DHCTs.

4. The method of claim 1, wherein the adjusting step further comprises:

decreasing the playout speed if the variation indicates that decoding in the DHCT precedes decoding in another one of the plurality of DHCTs.

5. The method of claim 1, further comprising:

receiving the indication of the desired playout time from another one of the plurality of DHCTs.

6. The method of claim 1, further comprising:

transmitting a channel change request to a channel change server; and

receiving the indication of the desired playout time from the channel change server.

7. A digital home communication terminal (DHCT) comprising:

a network interface configured to receive a media stream of encoded frames;

a decoder having a playout speed and configured to decode each of the encoded frames into a decoded frame at a corresponding target playout time;

logic configured to determine a target playout time for at least a first portion of the encoded frames;

synchronization logic configured to;

detect a channel change command associated with a target channel;

detect reception of a unicast Internet Protocol (IP) stream associated with the target channel;

responsive to the unicast detection, enter a synchronization mode in which the synchronization logic is further configured to;

determine a desired playout time for at least a second portion of the encoded frames;

determine a variation between the target playout time and the desired playout time; and

adjust the decoder playout speed to reduce the variation.

8. The system of claim 7, wherein the indication of the desired playout time of a frame corresponds to the actual playout time of the corresponding frame in another one of the plurality of DHCTs.

9. The system of claim 7, wherein the DHCT is part of a peer synchronization group, and the synchronization logic further comprises:

logic configured to determine the desired playout time for at least the second portion of the encoded frames from a stream transmitted by another DHCT in the peer synchronization group.

10. The system of claim 9, wherein the desired playout time is conveyed within an MPEG transport stream carried in the transmitted stream.

11. The system of claim 9, wherein the transmitted stream comprises IP packets, and the desired playout time is conveyed in one of the IP packets.

12. The system of claim 7, further comprising:

logic configured to detect reception of a multicast IP stream associated with the target channel; and

logic configured to exit the synchronization mode and reset the decoder playout speed in response to the multicast detection.

13. The system of claim 7, further comprising:

logic configured to detect a convergence between the target playout time and the desired playout time;

logic configured to exit the synchronization mode and reset the decoder playout speed in response to the convergence detection.

14. A computer-readable medium having a computer program for processing data comprising:

logic configured to decode a stream of encoded media frames at a playout speed, at least a first portion of the frames having a target playout time conveyed in the stream;

logic configured to receive an indication of a desired playout time for at least a second portion of the frames;

logic configured to determine a variation between the target playout time and the desired playout time; and

logic configured to adjust the playout speed to reduce the variation.

15. The computer-readable medium of claim 14, further comprising:

logic configured to increase the playout speed if the variation indicates that decoding lags behind decoding by a decoder in a peer synchronization group.

16. The computer-readable medium of claim 14, further comprising:

logic configured to decrease the playout speed if the variation indicates that decoding precedes decoding by a decoder in a peer synchronization group.

17. The computer-readable medium of claim 14, further comprising:

logic configured to receive the indication of the desired playout time from a peer in a synchronization group.

18. The computer-readable medium of claim 14, further comprising:

logic configured to transmit a channel change request to a channel change server; and

logic configured to receive the indication of the desired playout time from the channel change server.

19. The computer-readable medium of claim 14, further comprising:

logic configured to detect reception of a multicast IP stream associated with the target channel; and

logic configured to exit the synchronization mode and reset the decoder playout speed in response to the multicast detection.

20. The computer-readable medium of claim 14, further comprising:

logic configured to detect a convergence between the target playout time and the desired playout time;

logic configured to exit the synchronization mode and reset the decoder playout speed in response to the convergence detection.