Method and system for synchronizing the output of terminals

Patent metadata

Field	Value
Publication number	US-9237179-B2
Application number	US-74613308-A
Country	US
Kind code	B2
Filing date	Dec 5, 2008
Priority date	Dec 5, 2007
Publication date	Jan 12, 2016
Grant date	Jan 12, 2016

Abstract

A Method is described for synchronizing the output of terminals. The method according to the invention may be used in a system comprising a station, which transmits a packetized stream to at least a first and second terminal. Each terminal comprises a variable delay unit and each terminal is connected through a low-delay communication channel to at least one synchronization unit for calculating delay information. Further, each terminal is capable of determining media reference information of a received media unit from the stream. The method comprising the steps of providing one or more low delay communication channels between the terminals and a synchronization unit; the synchronization unit calculating delay information on the basis of synchronization information received from the terminals via the one or more low delay communication channels; and transmitting the delay information to at least one of the terminals allowing the at least one terminal to delay its output such that the output of the terminals are substantially synchronized.

First claim

The invention claimed is:

1. A method for synchronizing outputs of at least two terminals, the method comprising:
establishing one or more low delay communication channels between the terminals and a synchronization unit, the synchronization unit being comprised in one of the at least two terminals, and the one or more low delay communication channels being established as part of a communication session between the terminals;
at the synchronization unit, receiving respective synchronization information from each of the terminals via the one or more low delay communication channels, the respective synchronization information comprising indicia of a respective arrival time at each terminal of a respective media unit in a respective input stream;
the synchronization unit calculating delay information on the basis of the respective synchronization information received from the terminals; and
transmitting the delay information to at least one of the terminals, the delay information providing a basis for the at least one terminal to delay its output such that the outputs of the terminals are synchronized to within a threshold level.

2. The method according to claim 1 , wherein each terminal comprises an input for receiving a multi-media signal and an output for transmitting the multi-media signal to an information presentation unit and wherein each terminal comprises a variable delay unit for delaying the multi-media signal between the input and the output, the method further comprising:
transmitting a multi-media stream to the input of the terminals, the multi-media stream comprising media units, via a communication channel different than the low delay communication channel;
delaying the output of the multi-media signal according to the received delay information.

3. The method according to claim 1 , wherein the method further comprises:
the synchronization unit receiving synchronization information from each terminal in response to a synchronization request transmitted by the synchronization unit via the low delay communication channel, the synchronization information comprising media unit reference (MUR) information representing a position of a media unit in a multi-media stream at the respective terminals.

4. The method according to claim 3 , wherein the MUR information comprises a frame number or a sequence number of a frame received by the terminal at substantially a same time as receiving the synchronization request.

5. The method according to claim 3 , wherein the method further comprises:
adding one or more time stamps to the MUR information received from each respective terminal;
obtaining information on a frame rate of the multi-media stream received by the respective terminals; and
calculating the delay information for each terminal on the basis of the frame rate information and the time-stamped MUR information.

6. The method according to claim 3 , wherein the method further comprises:
the synchronization unit simultaneously sending one or more synchronization requests via the one or more low delay communication channels to the respective terminals;
obtaining information on a frame rate of the multi-media stream received by the respective terminals; and
calculating the delay information for each terminal on the basis of the frame rate information and the MUR information.

7. The method according to claim 1 , wherein the one or more low delay communication channels are established as part of a broadcast session as defined in ETSI TS 182 027.

8. The method according to claim 1 , wherein the one or more low delay communication channels are selected from the group consisting of a Voice over IP (VoIP) channel, an USSD based channel over a GSM, a UMTS or LTE network, an QoS-controlled channel in an IMS session, a dedicated channel in a communication session or a broadcast session, a dedicated Ethernet VLAN channel, a dedicated MPLS channel, and a dedicated channel used by an IP Diffserv stream.

9. The method according to claim 1 , wherein the synchronization unit is located in a server separate from the terminals or in one or more of the terminals.

10. A system for synchronizing outputs of at least two terminals, the system comprising a synchronization unit connected via one or more low delay communication channels to the at least two terminals, wherein the one or more low delay communication channels are established as part of a communication session between the terminals, and wherein the synchronization unit is comprised in one of the at least two terminals and is configured to (i) receive respective synchronization information from each of the terminals via the one or more low delay communication channels, wherein the respective synchronization information comprises indicia of a respective arrival time at each terminal of a respective media unit in a respective input stream, (ii) calculate delay information on the basis of the respective synchronization information received from the at least two terminals and (iii) transmit the delay information to at least one of the terminals, the delay information providing a basis for the at least one terminal to delay its output such that the outputs of the at least two terminals are synchronized to within a threshold level.

11. The system according to claim 10 , wherein each terminal comprises an input for a receiving multi-media signal and an output for transmitting the multi-media signal to an information presentation unit and a variable delay unit for delaying the multi-media signal between the input and the output according to the delay information, the system further comprising a transmitting station transmitting a multimedia stream to the terminals, the multi-media stream comprising media units.

12. A synchronization unit comprising:
a receiver for receiving respective synchronization information from at least two terminals via one or more low delay communication channels, wherein the one or more low delay communication channels are established as part of a communication session between the terminals, and wherein the respective synchronization information comprises indicia of a respective arrival time at each terminal of a respective media unit in a respective input stream;
a processor configured to calculate delay information on the basis of the received respective synchronization information; and,
a transmitter for transmitting the delay information to at least one of the terminals, wherein the delay information provides a basis for the at least one terminal to delay its output such that the outputs of the terminals are synchronized to within a threshold level,
wherein the synchronization unit is comprised in one of the at least two terminals.

13. A terminal comprising:
a receiver;
a transmitter;
a variable delay unit;
one or more computing devices;
memory accessibly by the one or more computing devices; and
software code portions stored in the memory that when executed by the one or more computing devices cause the terminal to carry out functions including:
the receiver receiving a synchronization request from a synchronization unit, delay information via one or more low delay communication channels, and a multi-media stream via a communication channel different from the low delay communication channel, wherein the one or more low delay communication channels are established as part of a communication session between the terminals,
the transmitter transmitting synchronization information via the one or more low delay communication channels to the synchronization unit, and transmitting at least one media unit in the received multi-media stream to an information presentation unit, wherein

Assignees

• Stokking Hans Maarten
• Van Deventer Mattijs Oskar
• Walraven Fabian Arthur
• Niamut Omar Aziz
• Koninkl Kpn Nv
• TNO

Inventors

• Stokking Hans Maarten
• Van Deventer Mattijs Oskar
• Walraven Fabian Arthur
• Niamut Omar Aziz

Classifications

• H04L65/80 Primary

  Responding to QoS · CPC title

• H04J3/0661

  using timestamps · CPC title

• H04J3/0682

  by delay compensation, e.g. by compensation of propagation delay or variations thereof, by ranging · CPC title

• H04L65/1094

  Inter-user-equipment sessions transfer or sharing · CPC title