Synchronizing multi-channel speakers over a network

• US 7,805,210 B2
• Filed: 11/10/2005
• Issued: 09/28/2010
• Est. Priority Date: 11/18/2004
• Status: Active Grant

• Current Assignee: DTS Licensing Limited (Adeia Inc.)
• Original Assignee: National University of Ireland Galway
• Inventors: Cucos, Alex, Corcoran, Peter
• Primary Examiner(s): Flanders; Andrew C
• Application Number:
  US11/667,585
• Publication Number:
  US 20070297459A1
• Time in Patent Office: 1,783 Days
• Field of Search: 700/94, 715/202, 715/203, 715/500.1, 715/723, 715/808
• US Class Current: 700/94
• CPC Class Codes: H04J 3/07 using pulse stuffing for systems with different or fluctuating information rates or bit rates
• 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 server is arranged to distribute at least one stream of audio data corresponding to an audio signal to two or more speakers across a network. Each speaker includes a respective clock for regenerating the audio signal from the audio data. For each speaker, the server determines a relative rate of the speaker clock to a real time rate; and for each stream of data provided to a speaker, the server determines from a respective relative rate, respective samples of the audio signal to be altered in accordance with said relative rate. The streams are altered accordingly and transmitted across the network.

Claims

1. A method operable in a server arranged to distribute at least one stream of audio data corresponding to an audio signal to two or more speakers across a network, each speaker including a respective clock for re-generating said audio signal from said audio data, said method comprising the steps of:

for each speaker, determining a relative rate of said speaker clock to a real time rate;

for each stream of data provided to a speaker, determining from a respective relative rate,

respective samples of said audio signal to be altered in accordance with said relative rate;

altering said streams in accordance with said determining step; and

transmitting said altered audio streams across said network.

2. A method according to claim 1 wherein the altering step comprises amending each stream by adding, deleting or duplicating said determined samples.

3. A method according to claim 1 wherein the altering step comprises including in respective audio streams, indications of audio samples which are to be added, deleted or duplicated during re-generation of said audio signal in a speaker.

4. A method according to claim 3 wherein said indications are included in headers of packets including audio sample data.

5. A method according to claim 1 in which altering said streams comprises one or more of:

adding or removing one or more samples from a silent period of said audio signal;

adding or removing one or more samples from a slowly changing period of said audio signal; and

averaging two more samples to provide fewer samples for a period of said audio signal.

6. A method according to claim 1 further comprising synchronizing said speakers in real-time using NTP (Network Time Protocol).

7. A method according to claim 1 wherein said determining comprises determining said relative rates using RTCP (Real-Time Control Protocol).

8. A method according to claim 1 further comprising the step of periodically sensing an ambient temperature and determining said relative rate according to said ambient temperature.

9. A server arranged to distribute at least one stream of audio data corresponding to an audio signal to two or more speakers across a network, each speaker including a respective clock for re-generating said audio signal from said audio data, said server being arranged:

for each speaker, to determine a relative rate of said speaker clock to a real time rate;

for each stream of data provided to a speaker, to determine from a respective relative rate, respective samples of said audio signal to be altered in accordance with said relative rate;

to alter said streams in accordance with said determining step; and

to transmit said altered audio streams across said network.

10. A server according to claim 9 arranged to transmit said altered audio streams data across a wireless network.