Method and device for the synchronised restitution of data flows

• US 7,710,941 B2
• Filed: 11/04/2003
• Issued: 05/04/2010
• Est. Priority Date: 11/06/2002
• Status: Active Grant

• Current Assignee: Sonos, Inc.
• Original Assignee: Barix AG
• Inventors: Sauter, Silvan, Staheli, Reto, Rietschel, Johannes
• Primary Examiner(s): Wilson; Robert W
• Application Number:
  US10/533,795
• Publication Number:
  US 20060013208A1
• Time in Patent Office: 2,373 Days
• Field of Search: 370/350, 370/395.64, 370/503, 386/66
• US Class Current: 370/350
• CPC Class Codes: H04J 3/0641 Change of the master or reference, e.g. take-over or failure of the master
• CPC Class Codes: H04J 3/0664 unidirectional timestamps
• CPC Class Codes: H04J 3/0667 Bidirectional timestamps, e.g. NTP or PTP for compensation of clock drift and for compensation of propagation delays arrangements for monitoring round trip delays in packet switching networks H04L43/0864
• CPC Class Codes: H04L 12/1877 Measures taken prior to transmission
• CPC Class Codes: H04L 65/1101 Session protocols
• CPC Class Codes: H04L 65/764 at the destination reformatting of additional data in video clients H04N21/4355
• CPC Class Codes: H04R 2227/003 Digital PA systems using, e.g. LAN or internet
• CPC Class Codes: H04R 2227/005 Audio distribution systems for home, i.e. multi-room use
• CPC Class Codes: H04R 2420/07 Applications of wireless loudspeakers or wireless microphones
• CPC Class Codes: H04R 27/00 Public address systems circuits for preventing acoustic reaction H04R3/02; circuits for distributing signals to loudspeakers H04R3/12; monitoring or testing arrangements for public address systems H04R29/007; amplifiers H03F

Abstract

A method for restitution of data flows or data packets transmitted over a network, using at least two restitution appliances that are at least indirectly connected to the network, for a synchronized and error-free restitution. To synchronize the restitution by the at least two restitution appliances, either one of the restitution appliances, as the master, provides its internal clock as the reference, and the other restitution appliances, as the slaves, coordinate their internal clock with that of the master by the network and restitute the data flows or data packets according to the coordinated clock, or the internal clock of an external appliance also available on the network is used as the master, and all restitution appliances, as the slaves, co-ordinate their internal clock with that of the master by the network, and restitute the data flows or data packets according to the coordinated clock.

Claims

1. A method for reproducing data streams or data packets transmitted via at least one network using at least two reproduction units that are at least indirectly linked to the network, the method comprising:

transmitting data packets between the at least two reproduction units asynchronously;

buffering data packets in the at least two reproduction units dynamically so as to be matched to the circumstances of the network;

synchronizing reproduction using the at least two reproduction units, wherein the reproduction units are synchronized in a range below 100 ms,

either by virtue of one of the reproduction units, as a master, prescribing its internal clock as a reference and at least one other reproduction unit, as a slave, aligning its internal clock with that of the master via the network or carrying a copy of the master clock and reproducing data streams or data packets based on this aligned clock,

or by virtue of the internal clock of an external unit available on the network being used as the master and all reproduction units, as slaves, aligning their internal clocks with that of the master via the network and reproducing data streams or data packets based on this aligned clock,

wherein at least some of the data streams or data packets are temporarily buffered in the reproduction units before reproduction, with audio files involving buffering in a range of approximately 1to 5 sec; and

aligning the clock on each slave before reproduction for the first time and updating the clock periodically during the reproduction, the periodic update being performed on the slave for systematically matching the speed of operation of the internal clock in the slave to that of the master in order to compensate for differences in the internal propagation-time characteristics of the master and the slave,

wherein the internal clock in the slave is aligned by virtue of the internal clock in the master being requested by the slave, a plurality of times, and by virtue of at least one data packet, that may be identical to the packets for requesting the time on the master, being transmitted from the slave to the master and being sent back, and the internal clock in the slave being brought into line with the clock in the master on the basis of a mean propagation time, calculated as a mean taking into account handling times in the units, for data packets between the master and the slave.

2. The method as claimed in claim 1, wherein a first of the reproduction units that has a task of reproduction is automatically defined as the master.

3. The method as claimed in claim 1, wherein the data streams or data packets are at least one of digital audio, video data, a combination of digital audio or video data, compressed or uncompressed audio files of MP3, WAV, MPEG, or Windows Media.

4. The method as claimed in claim 3, wherein either same data are reproduced on the reproduction units or different channels of the data, in a case audio files in stereo format or multichannel, are reproduced on different reproduction units.

5. The method as claimed in claim 1, wherein the individual reproduction units are synchronized in a range of at least one of below 10 ms, or below 2 ms, or below 1 ms.

6. The method as claimed in claim 1, wherein the network is a wireless network or a radio network.

7. The method as claimed in claim 1, wherein during the reproduction by at least one reproduction unit at least one further reproduction unit is switched in synchronously by virtue of the unit that has been switched in automatically aligning itself with the present master and starting reproduction itself after buffering some of the data.

8. The method as claimed in claim 1, wherein the data packets or data streams are either fetched from a separate data server, or are fetched on one of the reproduction units, or are already available on the reproduction units, or are made available to the system in digital form via an analog/digital converter and/or a compression/coding unit after supply in analog or digital form.

9. The method as claimed in claim 1, wherein the data packets or data streams are read from a data source into a ring buffer in the master, with each byte read in being provided with a unique address, and wherein, in a process that is independent of the data streams being read into the ring buffer, the master sends the data to the network from the ring buffer in blocks, straight after reading in, by broadcast, or by UDP broadcast, or by multicast, with an addition of a protocol header that includes an address of a first byte sent, a precise master time, and an address of the next byte that is to be sent by the master to a codec of the master.

10. The method as claimed in claim 9, wherein the address of the next byte that is to be sent by the master to the codec of the master is sent at least partly in independent control blocks, which may be identical to control blocks for checking the clock on the master.

11. The method as claimed in claim 1, further comprising:

sending a lost data portion again, to protect data integrity when a slave establishes that a data portion has been lost on the network, by the master upon a request from the slave, with the master performing this repeated sending only after a delay, and with the slaves making the requests in staggered fashion such that identical requests are sent only once over the network.

12. The method as claimed in claim 1, wherein the data streams or data packets are used to send a bit rate of the master at which the master provides the data streams or data packets on the network, the reproduction unit using the sent bit rate to ascertain the delays that arise in the network.

13. The method as claimed in claim 1, wherein at least one of the reproduction units has a memory that is used as a source of audio data, content of the audio data being obtained from the master or from another data source.

23. The method as claimed in claim 1, wherein at least one of the reproduction units is for its part used as a master for a subnetwork, with appropriate repetitions being forwarded to a topmost master.

14. A method for reproducing data streams or data packets transmitted via at least one network using at least two reproduction units which are at least indirectly linked to the network, the method comprising:

synchronizing reproduction using the at least two reproduction units,

either by virtue of one of the reproduction units, as master, prescribing an internal clock of the master as reference and the other reproduction units, as slaves, aligning internal clocks of slaves with that of the master via the network or carrying a copy of the master clock and reproducing data streams or data packets on the basis of this aligned clock,

or by virtue of the internal clock of an external unit which is likewise available on the network being used as the master and all reproduction units, as slaves, aligning their internal clock with that of the master via the network and reproducing data streams or data packets on the basis of this aligned clock,

wherein the data streams or data packets are used to send at least one command to the reproduction units together with an associated execution time, the execution time being set to a time between the transfer of the command to the network and the execution time which is greater than a longest network delay time between the master and the slaves.

15. The method as claimed in claim 14, wherein the network is a network in which data packets are transmitted asynchronously or synchronously.

16. The method as claimed in claim 14 further comprising:

aligning the clock of the slave before reproduction for a first time; and

updating the clock periodically during the reproduction.

17. The method as claimed in claim 14, wherein the periodic update is used on the slave for systematically matching a speed of operation of the internal clock in the slave to that of the master to compensate for differences in internal propagation-time characteristics of the master and slave.

18. The method as claimed in claim 17, wherein the systematic matching involves scaling the internal clock in the slave using a constant correction factor.

19. The method as claimed in claim 14, wherein the internal clock is aligned by virtue of the internal clock in the master being requested by the slave, a plurality of times, and by virtue of at least one data packet that may be identical to the packets for requesting the time on the master, being transmitted from the slave to the master and being sent back, and the internal clock in the slave being brought into line with the clock in the master based on a propagation time or an average propagation time for data packets between master and slave.

20. The method as claimed in claim 14, wherein the propagation time is calculated as a mean taking into account handling times in the reproduction units.

21. The method as claimed in claim 14, further comprising:

buffering data packets in the at least two reproduction units dynamically so as to be matched to circumstances of the network.

22. A method for reproducing data streams or data packets transmitted via at least one network using at least two reproduction units which are at least indirectly linked to the network, the method comprising:

synchronizing reproduction using the at least two reproduction units,

either by virtue of one of the reproduction units, as master, prescribing an internal clock of the master as a reference and the other reproduction units, as slaves, aligning internal clock of the slaves with that of the master via network or carrying a copy of the master clock and reproducing data streams or data packets on the basis of this aligned clock,

or by virtue of the internal clock of an external unit, which is likewise available on the network being used as the master and all reproduction units, as slaves, aligning their internal clock with that of the master via the network and reproducing data stream or data packets on the basis of this aligned clock, wherein

a reproduction unit that has been switched in transfers the data streams or data packets received from the network directly to a codec,

the codec rejects the supplied data by muting until the codec detects a first valid frame, the codec is stopped when the codec detects the first valid frame and the current byte is noted, and

the codec is the reproduction unit processes the data stream or the data packets again and is switched to reproduction when this current byte is played on the master, after the codec is stopped and the current byte is noted.

24. A non-transitory computer readable medium containing program instructions for execution on a computer which when executed by a processor causes the computer to perform the method comprising:

transmitting data packets between the at least two reproduction units asynchronously;

buffering data packets in the at least two reproduction units dynamically so as to be matched to the circumstances of the network;

synchronizing reproduction using the at least two reproduction units, wherein the reproduction units are synchronized in a range below 100 ms,

either by virtue of one of the reproduction units, as a master, prescribing its internal clock as a reference and at least one other reproduction unit, as a slave, aligning its internal clock with that of the master via the network or carrying a copy of the master clock and reproducing data streams or data packets based on this aligned clock,

or by virtue of the internal clock of an external unit available on the network being used as the master and all reproduction units, as slaves, aligning their internal clocks with that of the master via the network and reproducing data streams or data packets based on this aligned clock,

wherein at least some of the data streams or data packets are temporarily buffered in the reproduction units before reproduction, with audio files involving buffering in a range of approximately 1to 5 sec; and

aligning the clock on each slave before reproduction for the first time and updating the clock periodically during the reproduction, the periodic update being performed on the slave for systematically matching the speed of operation of the internal clock in the slave to that of the master in order to compensate for differences in the internal propagation-time characteristics of the master and the slave,

wherein the internal clock in the slave is aligned by virtue of the internal clock in the master being requested by the slave, a plurality of times, and by virtue of at least one data packet, that may be identical to the packets for requesting the time on the master, being transmitted from the slave to the master and being sent back, and the internal clock in the slave being brought into line with the clock in the master on the basis of a mean propagation time, calculated as a mean taking into account handling times in the units, for data packets between the master and the slave.

25. A reproduction unit configured to reproduce data streams or data packets via an output unit transmitted via at least one network, in which data packets are transmitted asynchronously, using at least two reproduction units which are at least indirectly linked to the network via a network interface, comprising:

The network interface configured to indirectly link the reproduction unit to at least one additional reproduction unit over the network;

A central computer unit configured to automatically integrate the reproduction unit into the network, and including a memory storing a permanently programmed data processing program that is activated automatically after a power supply is turned on, the central computer unit being configured to synchronize reproduction of the data stream or data packets with the at least one additional reproduction unit, the reproduction time difference between the reproduction unit and the at least one additional reproduction unit being 100 ms, either

by virtue of one of the reproduction units, as a master, prescribing an internal clock of the master as a reference and at least one other reproduction unit as a slave, aligning an internal clock of the slave with that of the master via the network or carrying a copy of the master clock, and reproducing the data streams or data packets based on this aligned clock,

or by virtue of the internal clock of an external unit available on the network being used as the master and all reproduction units, as slaves, aligning their internal clocks with that of the master via the network and reproducing the data streams or data packets based on this aligned clock; and

the output unit to at least indirectly output the data streams or data packets, wherein

at least some of the data streams or data packets are temporarily buffered in the reproduction units before reproduction, with audio files involving buffering in the range of approximately 1to 5sec, the buffering being performed dynamically so as to be matched to the circumstances of the network,

the clock on each slave is aligned before reproduction for the first time and is updated periodically during the reproduction, the periodic update being used on the slave for systematically matching the speed of operation of the internal clock in the slave to that of the master in order to compensate for differences in the internal propagation-time characteristics of the master and the slave, and

the internal clock in the slave is aligned by virtue of the internal clock in the master being requested by the slave, a plurality of times, and by virtue of at least one data packet, that may be identical to the packets for requesting the time on the master, being transmitted from the slave to the master and being sent back, and the internal clock in the slave being brought into line with the clock in the master on the basis of a mean propagation time, calculated as a mean taking into account handling times in the units, for data packets between the master and the slave.