Synchronous play-out of media data packets

• US 20040228367A1
• Filed: 09/04/2003
• Published: 11/18/2004
• Est. Priority Date: 09/06/2002
• Status: Active Grant

• Current Assignee: Sony Deutschland GmbH (Sony Group Corp.)
• Original Assignee: Sony Deutschland GmbH (Sony Group Corp.)
• Inventors: Mosig, Rudiger
• Granted Patent: US 7,675,943 B2
• Time in Patent Office: Days
• US Class Current: 370/503
• CPC Class Codes: H04L 65/1101 Session protocols
• CPC Class Codes: H04L 65/612 for unicast
• CPC Class Codes: H04L 65/65 Network streaming protocols, e.g. real-time transport protocol [RTP] or real-time control protocol [RTCP]
• CPC Class Codes: H04L 65/80 Responding to QoS

Abstract

In a digital audio transmission system media data packets (1021, 1022) are sent from a media source (101) to media sinks (e.g. loudspeakers) (1, 2). If a media data packet (1021, 1022) is received by a media sink (1, 2) and contains audio data belonging to an audio signal of e.g. a stereo signal, it is important that this media data packet (1021, 1022) is played-out at the same moment as a media data packet (1021, 1022) containing an audio signal of the same stereo signal received by another media sink (1, 2), i.e. the media data packets (1021, 1022) must be played-out synchronously. To ensure this synchronous play-out of media data packets (1021, 1022) in different media sinks (1, 2), a common play-out time (105) is determined by the media source (101) or the media sink (1, 2) and media data packets (1021, 1022) are buffered in a buffer (1041, 1042) until this common play-out time (105) is reached. The media source (101) or the media sink (1, 2) determine the common play-out time (105) on the basis of a global wallclock time, which is calculated on the basis of a sample clock time.

Claims

1. A media source (101;

400)

being capable of sending out time-stamped media data packets (1021, 1022;

308;

610S, 610R;

76, 77), in particular to one or more receiving media sink(s) (1, 2;

4021, 4022;

71, 72),

being adapted for

determining a play-out time offset (604R),

precisely determining a global wallclock time (201),

determining a common play-out time for each received time-stamped media data packet (1021, 1022;

308;

610S, 610R;

76, 77) by adding the time indicated by the timestamp (611R) of said timestamped media data packet (1021, 1022;

308;

610S, 610R;

76, 77) and said play-out time offset (604R), and

playing-out each received time-stamped media data packet (1021, 1022;

308;

610S, 610R;

76, 77) exactly when the determined common play-out time for the received time-stamped media data packet (1021, 1022;

308;

610S, 610R;

76, 77) is reached, the timestamp (611S) of each media data packet (1021, 1022;

308;

610S, 610R;

76, 77) being indicative for the time of creation of the respective media data packet (1021, 1022;

308;

610S, 610R;

76, 77),

being adapted for determining a play-out time offset (604S), and

being adapted for sending out the play-out time offset (604S), in particular to said one or more receiving media sink(s) (1, 2;

4021, 4022;

71, 72).

2. The media source (101;

400) according to claim 1,

characterized by

a sample clock being capable of determining a sample clock time,

being capable of determining a global wallclock time (201), and

being adapted for sending out a control packet (606S) once in a while, in particular to said one or more receiving media sink(s) (1, 2;

4021, 4022;

71, 72), said control packet (606S) comprising two control packet timestamps indicating the same moment in time, the first control packet timestamp (608S) of which being measured or defined in time units of said global wallclock time (201), the second control packet timestamp (607S) of which being measured or defined in time units of said sample clock time.

3. The media source (101;

400) according to claim 1,

characterized in that

said timestamp (611S) of a media data packet (1021, 1022;

308;

610S, 610R;

76, 77) is indicative for the time of creation of said time-stamped media data packet (1021, 1022;

308;

610S, 610R;

76, 77) in time units of said sample clock time.

4. The media source (101;

400) according to claim 1,

which is designed for sending out the same media data packets (1021, 1022;

308;

610S, 610R;

76, 77) to two or more different receiving media sinks (1, 2;

4021, 4022;

71, 72).

5. A media sink (1, 2;

4021, 4022;

71, 72)

adapted for receiving time-stamped media data packets (1021, 1022;

308;

610S, 610R;

76, 77), in particular from a media source (101;

400),

capable of sending out time-stamped media data packets (1021, 1022;

308;

610S, 610R;

76, 77), to one or more receiving media sink(s) (1, 2;

4021, 4022;

71, 72), the timestamp (611S) of each media data packet (1021, 1022;

308;

610, 610R, 76, 77) being indicative for the time of creation of the respective media data packet (1021, 1022;

308;

610, 610R;

76, 77),

being adapted for determining a play-out time offset (604S), and

being adapted for sending out the play-out time offset (604S), in particular to said one or more receiving media sink(s) (1, 2;

4021, 4022;

71, 72)

being adapted for

determining a play-out time offset (604R),

precisely determining a global wallclock time (201),

determining a common play-out time for each received time-stamped media data packet (1021, 1022;

308;

610S, 610R;

76, 77) by adding the time indicated by the timestamp (611R) of said timestamped media data packet (1021, 1022;

308;

610S, 610R;

76, 77) and said play-out time offset (604R), and

playing-out each received time-stamped media data packet (1021, 1022;

308;

610S, 610R;

76, 77) exactly when the determined common play-out time for the received time-stamped media data packet (1021, 1022;

308;

610S, 610R;

76, 77) is reached.

6. The media sink (1, 2;

4021, 4022;

71, 72) according to claim 5,

which is adapted for receiving said play-out time offset (604R) once, in particular from a said media source (101;

400).

7. The media sink (1, 2;

4021, 4022;

71, 72) according to claim 5,

which is adapted for negotiating said play-out time offset (604R) with at least one other said media sink (1, 2;

4021, 4022;

71, 72).

8. The media sink (1, 2;

4021, 4022;

71, 72) according to claim 5,

characterized by

being capable of

receiving a control packet (606R), in particular from said media source (101;

400), containing a first control packet timestamp (608R) indicating a certain moment in time measured or defined in time units of a sample clock time and a second control packet timestamp (607R) indicating the same certain moment in time measured or defined in time units of a global wallclock time (201), and of

converting a time indicated by a timestamp (611R) of a time-stamped media data packet (1021, 1022;

308;

610S, 610R;

76, 77) measured or defined in units of a sample clock time into a time measured or defined in units of a global wallclock time (201), based on the information of the first and second control packet timestamp.

9. The media sink (1, 2;

4021, 4022;

71, 72) according to claim 5,

characterized by

a buffer which is adapted for storing media data packets (1021, 1022;

308;

610S, 610R;

76, 77) until said common play-out time is reached.

10. A media processing system

characterized by

a media source (101;

400) according to

capable of sending out time-stamped media data packets (1021, 1022;

308;

610S, 610R;

76, 77), to one or more receiving media sink(s) (1, 2;

4021, 4022;

71, 72), the timestamp (611S) of each media data packet (1021, 1022;

308;

610S, 610R;

76, 77) being indicative for the time of creation of the respective media data packet (1021, 1022;

308;

610S, 610R;

76, 77),

being adapted for determining a play-out time offset (604S), and

being adapted for sending out the play-out time offset (604S), in particular to said one or more receiving media sink(s) (1, 2;

4021, 4022;

71, 72) and a media sink (1, 2;

4021, 4022;

71, 72)

being adapted for

determining a play-out time offset (604R),

precisely determining a global wallclock time (201),

determining a common play-out time for each received time-stamped media data packet (1021, 1022;

308;

610S, 610R;

76, 77) by adding the time indicated by the timestamp (611R) of said timestamped media data packet (1021, 1022;

308;

610S, 610R;

76, 77) and said play-out time offset (604R), and

playing-out each received time-stamped media data packet (1021 1022;

308;

610S, 610R;

76, 77) exactly when the determined common play-out time for the received time-stamped media data packet (1021, 1022;

308;

610S, 610R;

76, 77) is reached.

11. A media source (501)

being adapted for determining a play-out time offset and for determining a common play-out time by adding the determined play-out time offset to a current time, and

being adapted for sending out time-stamped media data packets (511) to one or more receiving media sink(s) (502), the timestamp (512) of a time-stamped media data packet (511) being indicative for said common play-out time of the media data packet.

12. The media source (501) according to claim 11,

characterized by

a sample clock being capable of determining a sample clock time, and

being adapted for calculating said current time by reading a global wallclock time (201) only once and adding time periods given by said sample clock to the only once read global wallclock time (201).

13. The media source (501) according to claim 11,

which is adapted for sending out the same media data packets (511) to two or more different receiving media sinks (502).

14. A media sink (502)

being adapted for receiving time-stamped media data packets (514), in particular from a media source (501) according to claim 11, and

being capable of

precisely determining a global wallclock time (201), and

determining a common play-out time for each received time-stamped media data packet (514) which is the time indicated by the timestamp (515) of the time-stamped media data packet (514).

15. The media sink (502) according to claim 14,

characterized by

a buffer which is adapted for storing media data packets (514) until said common play-out time is reached.

27. A method to enable the synchronous play-out of media data packets (511), intended for a media source (501), comprising the following steps

determining a play-out time offset and a common play-out time by adding the determined play-out time offset to a current time, and

sending out time-stamped media data packets (511), in particular to one or more receiving media sink(s) (502) according to claim 14, the timestamp (512) of a time-stamped media data packet being indicative for said common play-out time of the media data packet.

28. The method according to claim 27,

characterized by the steps of

determining a sample clock time, and

calculating said current time by reading a global wallclock time (201) only once and adding time periods given by said sample clock to the only once read global wallclock time (201).

29. The method according to claim 27,

16. A media processing system

characterized by

a media source (501)

being adapted for determining a play-out time offset and for determining a common play-out time by adding the determined play-out time offset to a current time, and

being adapted for sending out time-stamped media data packets (511) to one or more receiving media sink(s) (502), the timestamp (512) of a time-stamped media data packet (511) being indicative for said common play-out time of the media data packet and a media sink (502)

being adapted for receiving time-stamped media data packets (514), in particular from said media source (501) and

being capable of

precisely determining a global wallclock time (201), and

determining a common play-out time for each received time-stamped media data packet (514) which is the time indicated by the timestamp (515) of the time-stamped media data packet (514).

17. A method for playing-out media data packets (1021, 1022;

308;

610S, 610R;

76, 77) synchronously, intended for a media source (101;

400), comprising the following steps

sending out time-stamped media data packets (1021, 1022;

308;

610S, 610R;

76, 77), in particular to one or more receiving media sink(s) (1, 2;

4021, 4022;

71, 72)

being adapted for

determining a play-out time offset (604R),

precisely determining a global wallclock time (201),

determining a common play-out time for each received time-stamped media data packet (1021, 1022;

308;

610S, 610R;

76, 77) by adding the time indicated by the timestamp (611R) of said timestamped media data packet (1021, 1022;

308;

610S, 610R;

76, 77) and said play-out time offset (604R), and

playing-out each received time-stamped media data packet (1021, 1022;

308;

610S, 610R;

76, 77) exactly when the determined common play-out time for the received time-stamped media data packet (1021, 1022;

308;

610S, 610R;

76, 77) is reached, the timestamp (611S) of each media data packet (1021, 1022;

308;

610S, 610R;

76, 77) being indicative for the time of creation of the respective media data packet (1021, 1022;

308;

610S, 610R;

76, 77),

determining a play-out time offset (603S), and

sending out the play-out time offset (604S), in particular to said one or more receiving media sink(s) (1, 2;

4021, 4022;

71, 72).

18. The method according to claim 17,

characterized by the following steps,

determining a sample clock time,

determining a global wallclock time (201), and

sending out a control packet (606S) once in a while, in particular to said one or more receiving media sink(s) (1, 2;

4021, 4022;

71, 72), said control packet (606S) comprising two control packet timestamps indicating the same moment in time, the first control packet timestamp (608S) of which being measured or defined in time units of said global wallclock time (201), the second control packet timestamp (607S) of which being measured or defined in time units of said sample clock time.

19. The method according to claim 17,

characterized in that

said timestamp (611S) of a media data packet (1021, 1022;

308;

610S, 610R;

76, 77) is indicative for the time of creation of said time-stamped media data packet (1021, 1022;

308;

610S, 610R;

76, 77) in time units of said sample clock time.

20. The method according to claim 17,

characterized by

sending out the same media data packets (1021, 1022;

308;

610S, 610R;

76, 77) to two or more different receiving media sinks (1, 2;

4021, 4022;

71, 72).

21. A method for playing-out media data packets (1021, 1022;

308;

610S, 610R;

76, 77) synchronously, intended for a media sink (1, 2;

4021, 4022;

71, 72), comprising the following steps

receiving time-stamped media data packets (1021, 1022;

308;

610S, 610R;

76, 77), in particular from a media source (101;

400)

capable of sending out time-stamped media data packets (1021, 1022;

308;

610S, 610R;

76, 77), to one or more receiving media sink(s) (1, 2;

4021, 4022;

71, 72), the timestamp (611S) of each media data packet (1021, 1022;

308;

610S, 610R;

76, 77) being indicative for the time of creation of the respective media data packet (1021, 1022;

308;

610S, 610R;

76, 77),

being adapted for determining a play-out time offset (604S), and

being adapted for sending out the play-out time offset (604S), in particular to said one or more receiving media sink(s) (1, 2;

4021, 4022;

71, 72)

determining a play-out time offset (604R),

precisely determining a global wallclock time (201),

determining a common play-out time for each received time-stamped media data packet (1021, 1022;

308;

610S, 610R;

76, 77) by adding (614R) the time indicated by the timestamp (611R) of said timestamped media data packet (1021, 1022;

308;

610S, 610R;

76, 77) and said play-out time offset (604R), and

playing-out each received time-stamped media data packet (1021, 1022;

308;

610S, 610R;

76, 77) exactly when the determined common play-out time for the received time-stamped media data packet (1021, 1022;

308;

610S, 610R;

76, 77) is reached (616R).

22. The method according to claim 21,

characterized by the step of

receiving said play-out time offset (604R) once, in particular from said media source (101;

400).

23. The method according to claim 21,

characterized by the step of

negotiating said play-out time offset (604R) with at least one other media sink (1, 2;

4021, 4022;

71, 72)

being adapted for

determining a play-out time offset (604R),

precisely determining a global wallclock time (201),

determining a common play-out time for each received time-stamped media data packet (1021, 1022;

308;

610S, 610R;

76, 77) by adding the time indicated by the timestamp (611R) of said timestamped media data packet (1021, 1022;

308;

610S, 610R;

76, 77) and said play-out time offset (604R), and

playing-out each received time-stamped media data packet (1021, 1022;

308;

610S, 610R;

76, 77) exactly when the determined common play-out time for the received time-stamped media data packet (1021, 1022;

308;

610S, 610R;

76, 77) is reached.

24. The method according to claim 21,

characterized by the following steps,

receiving a control packet (606S), in particular from said media source (101;

400), containing a first control packet timestamp (608R) indicating a certain moment in time measured or defined in time units of a sample clock time and a second control packet timestamp (607R) indicating the same certain moment in time measured or defined in time units of a global wallclock time (201), and of

converting a time (613R) indicated by a timestamp (611R) of a time-stamped media data packet (1021, 1022;

308;

610S, 610R;

76, 77) measured or defined in units of a sample clock time into a time measured or defined in units of a global wallclock time (201), based on the information of the first and second control packet timestamp.

25. The method according to claim 21,

characterized by the step of

storing media data packets (1021, 1022;

308;

610S, 610R;

76, 77) in a buffer until said common play-out time is reached (615R).

26. A method for playing-out media data packets (1021, 1022;

308;

610S, 610R;

76, 77) synchronously, intended for a media processing system,

characterized by

the steps of

sending out time-stamped media data packets (1021, 1022;

308;

610S, 610R;

76, 77), in particular to one or more receiving media sink(s) (1, 2;

4021, 4022;

71, 72)

being adapted for

determining a play-out time offset (604R),

precisely determining a global wallclock time (201),

determining a common play-out time for each received time-stamped media data packet (1021, 1022;

308;

610S, 610R;

76, 77) by adding the time indicated by the timestamp (611R) of said timestamped media data packet (1021, 1022;

308;

610S, 610R;

76, 77) and said play-out time offset (604R), and

playing-out each received time-stamped media data packet (1021, 1022;

308;

610S, 610R;

76, 77) exactly when the determined common play-out time for the received time-stamped media data packet (1021, 1022;

308;

610S, 610R;

76, 77) is reached, the timestamp (611S) of each media data packet (1021, 1022;

308;

610S, 610R;

76, 77) being indicative for the time of creation of the respective media data packet (1021, 1022;

308;

610S, 610R;

76, 77),

determining a play-out time offset (603S), and

sending out the play-out time offset (604S), in particular to said one or more receiving media sink(s) (1, 2;

4021, 4022;

71, 72) and the steps of

receiving time-stamped media data packets (1021, 1022;

308;

610S, 610R;

76, 77), in particular from a media source (101;

400)

capable of sending out time-stamped media data packets (1021, 1022;

308;

610S, 610R;

76, 77), to one or more receiving media sink(s) (1, 2;

4021, 4022;

71, 72), the timestamp (611S) of each media data packet (1021, 1022;

308;

610S, 610R;

76, 77) being indicative for the time of creation of the respective media data packet (1021, 1022;

308;

610S, 610R;

76, 77),

being adapted for determining a play-out time offset (604S), and

being adapted for sending out the play-out time offset (604S), in particular to said one or more receiving media sink(s) (1, 2;

4021, 4022;

71, 72)

determining a play-out time offset (604R),

precisely determining a global wallclock time (201),

determining a common play-out time for each received time-stamped media data packet (1021, 1022;

308;

610S, 610R;

76, 77) by adding (614R) the time indicated by the timestamp (611R) of said timestamped media data packet (1021, 1022;

308;

610S, 610R;

76, 77) and said play-out time offset (604R), and

playing-out each received time-stamped media data packet (1021, 1022;

308;

610S, 610R;

76, 77) exactly when the determined common play-out time for the received time-stamped media data packet (1021, 1022;

308;

610S, 610R;

76, 77) is reached (616R).