Programmable audio mixer

• US 4,558,180 A
• Filed: 10/25/1983
• Issued: 12/10/1985
• Est. Priority Date: 10/25/1983
• Status: Expired due to Term

• Current Assignee: Bell Telephone Laboratories, Inc. (Nokia Corporation)
• Original Assignee: AT&T, Inc.
• Inventors: Scordo, Dominick
• Primary Examiner(s): BROWN, THOMAS
• Application Number:
  US06/545,162
• Time in Patent Office: 777 Days
• Field of Search: 179/18 BC, 179/2 TS, 179/2 TV, 370/62
• US Class Current: 379/202.01
• CPC Class Codes: H04M 3/561 by multiplexing
• CPC Class Codes: H04M 3/568 audio processing specific to telephonic conferencing, e.g. spatial distribution, mixing of participants echo suppression in two-way loud-speaking telephone systems H04M9/02; sound field processing per se H04S7/30

Abstract

Audio mixes for a plurality of conference locations are controllably obtained by using a matrix multiplication arrangement. The audio mixes for the individual conference locations are obtained by multiplying a dynamically determined gain matrix by an audio input matrix. Coefficient values in the gain matrix are dependent on whether incoming and outgoing transmission paths are assigned to a location and on whether an audio sample is being received or not.

Claims

1. Apparatus for generating mixed audio signals to be transmitted to a plurality of remote locations in a conference, wherein the remote locations include conference locations served by this apparatus and may include other apparatus for generating mixed audio signals to be transmitted to a plurality of remote locations, the apparatus comprising,

means for storing information indicating whether individual ones of incoming transmission paths to this apparatus and outgoing transmission paths from this apparatus are being used in the conference,

means for storing information indicating whether individual ones of the incoming transmission paths and the outgoing transmission paths are assigned to a conference location or to another apparatus for generating mixed audio signals, and

means responsive to said information for generating an appropriate audio mix for each conference location served by this apparatus and a partial sum of audio information from all the conference locations served by this apparatus to be transmitted to said other apparatus in the conference.

2. The apparatus as defined in claim 1 wherein said generating means includes means responsive to said incoming transmission path assignment information for identifying partial audio sums incoming from said other apparatus and means for combining said identified partial audio sums with audio information from the conference locations served by this apparatus to obtain appropriate audio mixes to be transmitted to each of the served conference locations.

3. The apparatus as defined in claim 2 wherein said generating means further includes means responsive to said outgoing transmission path assignment information for controllably generating the partial audio sum of audio information from conference locations served by this apparatus and means for controllably supplying said partial audio sum of the audio information from conference locations served by this apparatus to outgoing transmission paths from this apparatus assigned to said other apparatus.

4. The apparatus as defined in claim 3 further including means responsive to said incoming transmission path assignment information for selecting only one of any multiple partial audio sums received from any of the other apparatus in the conference.

5. The apparatus as defined in claim 3 further including means for transmitting said partial audio sum of the audio information from conference locations served by this apparatus over a plurality of outgoing transmission paths to said other apparatus in the conference.

6. The apparatus as defined in claim 1 wherein said generating means includes a controllable matrix multiplier.

7. The apparatus as defined in claim 6 wherein said controllable matrix multiplier controllably generates audio mixes and partial audio sums by multiplying a dynamically determined gain (loss) matrix by an audio input matrix, wherein said audio input matrix includes audio samples from conference locations served by this apparatus and partial sum audio samples from other such apparatus in the conference.

8. The apparatus as defined in claim 7 wherein said gain (loss) matrix includes a plurality of coefficients corresponding to incoming transmission paths to this apparatus and to outgoing transmission paths from this apparatus and further including means for dynamically setting any one of said coefficients to a predetermined value.

9. The apparatus as defined in claim 7 further including means for detecting when audio samples are being received on assigned incoming transmission paths to this apparatus and means for setting gain coefficients in said gain (loss) matrix to a first predetermined value when audio samples are being received and a second predetermined value when audio samples are not being received.

10. The apparatus as defined in claim 9 wherein said gain (loss) matrix includes a plurality of columns of coefficients, wherein each column corresponds to an incoming transmission path and a plurality of rows of coefficients, wherein each row corresponds to an outgoing transmission path.

11. The apparatus as defined in claim 10 further including means responsive to said assignment information for setting the coefficients in a corresponding column of the gain (loss) matrix to zero when an incoming transmission path is not assigned.

12. The apparatus as defined in claim 11 further including means responsive to said assignment information for setting the coefficients in a corresponding row of the gain (loss) matrix to zero when an outgoing transmission path is not assigned.

13. The apparatus as defined in claim 12 wherein audio information on said incoming transmission paths to this apparatus and outgoing transmission paths from this apparatus is in a first digital code format.

14. The apparatus as defined in claim 13 further including means for converting audio information on said incoming transmission paths from said first digital code format to a linear digital format and means for converting mixed audio information to be transmitted on said outgoing transmission paths from a linear digital code format to said first digital code format.

15. The apparatus as defined in claim 14 wherein said first digital code format is mu-law pulse code modulation (PCM) and said linear digital code format is linear PCM.