Method and System for Synchronizing the Output of Terminals

• US 20100257280A1
• Filed: 12/05/2008
• Published: 10/07/2010
• Est. Priority Date: 12/05/2007
• Status: Active Grant

• Current Assignee: Koninklijke KPN NV, Nederlandse Organisatie Voor Toegepast-Natuurwetenschappelijk Onderzoek Tno
• Original Assignee: Koninklijke KPN NV, Nederlandse Organisatie Voor Toegepast-Natuurwetenschappelijk Onderzoek Tno
• Inventors: Stokking, Hans Maarten, Walraven, Fabian Arthur, Niamut, Omar Aziz, van Deventer, Mattijs Oskar
• Granted Patent: US 9,237,179 B2
• Time in Patent Office: Days
• US Class Current: 709/231
• CPC Class Codes: H04J 3/0661 using timestamps
• CPC Class Codes: H04J 3/0682 by delay compensation, e.g. by compensation of propagation delay or variations thereof, by ranging
• CPC Class Codes: H04L 65/1094 Inter-user-equipment sessions transfer or sharing
• CPC Class Codes: H04L 65/80 Responding to QoS

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.

Claims

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 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 outputs of the terminals are substantially synchronized.

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 Diffsery 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 the 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 synchronization unit is configured to (i) calculate delay information on the basis of synchronization information received via the one or more low delay communication channels from the at least two terminals and (ii) transmit 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 at least two terminals are substantially synchronized.

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 synchronization information from at least two terminals via one or more low delay communication channels;

a processor configured to calculate delay information on the basis of the received synchronization information; and

,

a transmitter for transmitting the delay information to at least one of the terminals allowing the at least one terminal to delay its output such that the outputs of the terminals are substantially synchronized.

13. A terminal comprising:

a receiver configured to receive a synchronization request from a synchronization unit and delay information via one or more low delay communication channels and configured to receive a multi-media stream via a communication channel different from the low delay communication channel;

a transmitter configured to transmit synchronization information via the one or more low delay communication channels to the synchronization unit and configured to transmit the received multi-media signal to an information presentation unit; and

,

a variable delay unit for delaying transmission of the multi-media signal to the information presentation unit in accordance with the received delay information.

14. The terminal according to claim 13, wherein the terminal is a set-top box, a home computer, a mobile device, or a gaming console

15. The terminal according to claim 13, wherein the terminal further comprises a synchronization unit configured to calculate delay information on the basis of the synchronization information.

19. The terminal according to claim 13, wherein the synchronization information comprises media unit reference (MUR) information representing a position of a media unit in a multi-media stream at the terminal.

20. The terminal according to claim 19, 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.

16. An article of manufacture including a computer readable medium having instructions stored thereon that, in response to execution by a computing device, cause the computing device to perform operations comprising:

establishing one or more low delay communication channels between at least two terminals and a 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 outputs of the terminals are substantially synchronized.

17. The article of manufacture according to claim 16, the operations further comprising transmitting a synchronization request to the at least two terminals via the low delay communication channel and responsively receiving the synchronization information from the terminals;

wherein the synchronization information comprises media unit reference (MUR) information representing a position of a media unit in a multi-media stream at the respective terminals.

18. The article of manufacture according to claim 17, 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.