Arrangement and method for audio source tracking

• US 20050008169A1
• Filed: 04/07/2004
• Published: 01/13/2005
• Est. Priority Date: 05/08/2003
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Tandberg Telecom AS (Cisco Systems, Inc.)
• Inventors: Marton, Trygve Frederik, Johansen, Tom-Ivar, Muren, Petter
• Granted Patent: US 7,586,513 B2
• Time in Patent Office: Days
• US Class Current: 381/92
• CPC Class Codes: H04N 7/15 Conference systems
• 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

An arrangement and a method of localizing active speakers in a video conference includes a localization device that locates at least one microphone relative to the camera, while the at least one microphone in turn localizes the relative positions of audio sources. As the microphones are usually positioned close to the audio source in a video conference, the ratio of the distance between microphones relative to the distance between table microphone and audio source is reduced. Thus, the microphones are able to determine the positions of the audio sources with a higher resolution than if placed close to the camera. When the respective positions of the microphones relative to the camera and the audio source are known, the position of the audio source relative to the camera is then determined by means of geometrical calculations.

Claims

1. A method of localizing a position of an audio source relative to a camera, comprising steps of:

determining a position of the audio source relative to at least one of a microphone and array of microphone elements;

geometrically deriving a second distance and direction between the camera and one of the at least one of the microphone and array of microphone elements,

geometrically deriving a first distance and direction between the camera and the audio source from the position of the audio source relative to one of the at least one the microphone and array of microphone elements and said second distance and direction.

2. The method according to claim 1, wherein determining a position of the audio source relative to the at least one of the microphone and array of microphone elements includes:

detecting a respective time difference of receiving audio signals from the audio source to the at least one of the microphone and array of microphone elements for at least one of a pair of microphones, a pair of arrays of microphone elements, and a pair of a microphone and an array of microphone elements.

3. The method according to claim 1, wherein said second distance or direction between the camera and one of the at least one of the microphone and array of microphone elements is fixed.

4. The method according to claim 1, wherein deriving said second distance or direction between the camera and one of the at least one of the microphone and array of microphone elements, further comprises:

transmitting a sound signal from a known or detectable position relative to the camera;

respectively receiving the sound signal in at least two of the microphones and arrays of microphone elements;

processing the received sound signals for calculating said second distance or direction between the camera and one of the at least one of the microphone and array of microphone elements.

5. The method according to claim 1, wherein deriving said second distance or direction between the camera and one of the at least one of the microphone and array of microphone elements, further comprises:

providing said one of the at least one of the microphone and array of microphone elements with a recognizable pattern;

identifying the recognizable pattern within the view captured by the camera; and

determining said second distance or direction based on a size or a position of the recognizable pattern within the view.

6. The method according to claim 1, wherein determining the position of the audio source relative to the at least one of the microphone and array of microphone elements further comprises:

calculating a first time difference for receiving audio signals from the audio source to the respective microphones and arrays of microphone elements of each possible pair of microphones and arrays of microphone elements for each point in a predefined set of points;

measuring a second time difference for receiving audio signals from the audio source to the respective microphones and arrays of microphone elements of each possible pair of microphones and arrays of microphone elements;

calculating values of an error function for each point of the predefined set of points by summarizing the squared difference between the corresponding first and second time differences for each possible pair of microphones and arrays of microphone elements;

selecting a point associated with a least value of the error function as the position of the audio source.

7. The method according to claim 1, further comprising:

executing a look up with said first distance or direction in a table associating various distances and directions with corresponding camera zooming quantities and orientations, respectively; and

zooming or orienting the camera according to a result of said look up.

8. An arrangement for localizing a position of an audio source relative to a camera that determines a position of the audio source relative to at least one of a microphone and an array of microphone elements, including:

a control unit that geometrically derives a first distance or direction between the camera and the audio source from the position of the audio source relative to at least one of the microphone and array of microphone elements and a second distance or direction between the camera and one of the at least one of the microphone and array of microphone elements.

9. The arrangement according to claim 8, wherein the control unit is further configured to detect a respective time difference of receiving audio signals from the audio source to the at least one of the microphone and array of microphone elements for at least one of a pair of microphones, a pair of arrays of microphone elements, and a pair of a microphone and an array of microphone elements.

10. The arrangement according to claim 8, wherein said second distance or direction between the camera and one of the at least one of the microphone and array of microphone elements is fixed.

11. The arrangement according to claim 8, further comprising:

a sound signal transmitter positioned in a known or detectable position relative to said camera; and

a sound signal transceiver that receives sound in at least two of the microphones and arrays of microphone elements and transmits the received sound signals to the control unit, which is configured to process the received sound signals to calculate said second distance or direction between the camera and one of the at least one of the microphone and array of microphone elements.

12. The arrangement according to claim 8, wherein said one of the at least one of the microphone and array of microphone elements is provided with a recognizable pattern, the camera or the control unit is configured to identify the recognizable pattern within the view captured by the camera, and the control unit is configured to determine said second distance or direction based on a size or a position of the recognizable pattern within the view.

13. The arrangement according to claim 9, wherein the control unit is further configured to calculate a first time difference for receiving audio signals from the audio source to the respective microphones and arrays of microphone elements of each possible pair of microphones and arrays of microphone elements for each point in a predefined set of points, measure a second time difference for receiving audio signals from the audio source to the respective microphones and arrays of microphone elements of each possible pair of microphones and arrays of microphone elements, calculate values of an error function for each point of the predefined set of points by summarizing the squared difference between the corresponding first and second time differences for each possible pair of microphones and arrays of microphone elements, and select a point associated with a least value of the error function as the position of the audio source.

14. The arrangement according to claim 8, where the control unit includes a look up table associating various distances and directions with corresponding camera zooming quantities and orientations, respectively, and the control unit is configured to zoom or orient the camera according to a zooming quantity or orientation associated with said first distance or direction.