Processing audio signals using a state variable

• US 5,631,967 A
• Filed: 12/20/1994
• Issued: 05/20/1997
• Est. Priority Date: 11/24/1993
• Status: Expired due to Term

• Current Assignee: Intel Corporation
• Original Assignee: Intel Corporation
• Inventors: Marshall, Robert A., Wagner, Larry
• Primary Examiner(s): Chan, Wing F.
• Assistant Examiner(s): NGUYEN, DUC MINH
• Application Number:
  US08/359,692
• Time in Patent Office: 882 Days
• Field of Search: 379/201, 379/202, 379/204, 379/389, 379/410, 379/411, 379/408, 379/407, 379/406, 379/388, 381/98
• US Class Current: 381/98
• CPC Class Codes: G06T 1/00 General purpose image data processing
• CPC Class Codes: G06T 2200/16 involving adaptation to the client's capabilities
• CPC Class Codes: H04L 12/1813 for computer conferences, e.g. chat rooms instant messaging H04L51/04; protocols for multimedia communication H04L65/1101; arrangements for multi-party communication H04L65/403; telephonic conference arrangements H04M3/56; television conference systems H04N7/15
• CPC Class Codes: H04L 12/1822 Conducting the conference, e.g. admission, detection, selection or grouping of participants, correlating users to one or more conference sessions, prioritising transmission
• CPC Class Codes: H04M 3/567 Multimedia conference systems
• 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
• CPC Class Codes: H04M 7/006 Networks other than PSTN/ISDN providing telephone service, e.g. Voice over Internet Protocol (VoIP) , including next generation networks with a packet-switched transport layer H04L65/00 takes precedence; aspects not specific to the type of network H04M3/00; special services in those networks H04M3/42
• CPC Class Codes: H04M 9/08 Two-way loud-speaking telephone systems with means for conditioning the signal, e.g. for suppressing echoes for one or both directions of traffic
• CPC Class Codes: H04N 21/4143 embedded in a Personal Computer [PC]
• CPC Class Codes: H04N 21/643 Communication protocols network streaming protocols, e.g. real-time transport protocol [RTP] or real-time control protocol [RTCP], H04L65/65
• CPC Class Codes: H04N 7/148 Interfacing a video terminal to a particular transmission medium, e.g. ISDN
• CPC Class Codes: H04N 7/15 Conference systems
• CPC Class Codes: H04Q 2213/13003 Constructional details of switching devices
• CPC Class Codes: H04Q 2213/13103 Memory
• CPC Class Codes: H04Q 2213/13106 Microprocessor, CPU
• CPC Class Codes: H04Q 2213/13204 Protocols
• CPC Class Codes: H04Q 2213/13209 ISDN
• CPC Class Codes: H04Q 2213/1324 Conference call
• CPC Class Codes: H04Q 2213/13299 Bus
• CPC Class Codes: H04Q 2213/13337 Picturephone, videotelephony
• CPC Class Codes: H04Q 2213/13389 : LAN, internet

Abstract

A continuous stage variable is generated with a state machine of a controller. A level of transmit attenuation and a level of receive attenuation are generated by the controller using the continuous state variable. Local audio signals generated with a local microphone are attenuated with a transmit attenuator at the level of transmit attenuation for transmission to a remote node. Remote audio signals received from the remote node are attenuated with a receive attenuator at the level of receive attenuation for playback at a local speaker.

Claims

1. An apparatus for processing audio signals, comprising:

(a) a transmit attenuator for attenuating local audio signals generated by a local microphone for transmission to a remote node;

(b) a receive attenuator for attenuating remote audio signals received from the remote node for playback at a local speaker; and

(c) a controller for controlling a level of transmit attenuation for the transmit attenuator and a level of receive attenuation for the receive attenuator, the controller comprising a state machine that generates a scalar state variable, wherein

the controller uses the scalar state variable to control the level of transmit attenuation and the level of receive attenuation.

2. The apparatus of claim 1, wherein the controller controls the sum of the level of transmit attenuation and the level of receive attenuation to correspond to unity gain.

3. The apparatus of claim 1, wherein the controller controls the levels of transmit and receive attenuation based on:

an energy level for the local audio signals;

an energy level for local background noise;

an energy level for the remote audio signals; and

an energy level for remote background noise.

4. The apparatus of claim 1, wherein the state machine changes the scalar state variable at two or more different rates, where the different rates correspond to different configurations of the local and remote audio signals.

5. The apparatus of claim 1, wherein the state machine comprises a listen state, a talk state, and an idle state.

6. The apparatus of claim 5, wherein:

the state variable is a scalar state variable i;

when the scalar state variable i is between -j and -k, the state machine is in the listen state, wherein;

-j≦

i≦

j;

j is a specified positive constant; and

k is a specified positive constant less than j;

when the state scalar variable i is between k and j, the state machine is in the talk state; and

when the scalar state variable i is between -k and k, the state machine is in the idle state.

7. The apparatus of claim 6, wherein:

when the state machine is in the listen state, the controller sets the level of transmit attenuation to 0 and the level of receive attenuation to 1;

when the state machine is in the talk state, the controller sets the level of transmit attenuation to 1 and the level of receive attenuation to 0;

when the state machine is in the idle state, the controller sets the level of transmit attenuation to α and

the level of receive attenuation to (1-α

), wherein 0≦

α

≦

1.

8. The apparatus of claim 7, wherein, when the state machine is in the idle state, α

=(i+k) /2k.

9. The apparatus of claim 1, wherein the state machine comprises a no talking mode, a single talk (local) mode, a single talk (remote) mode, a double talk (local wins) mode, and a double talk (remote wins) mode.

10. The apparatus of claim 9, wherein:

if (T≦

τ

_L) &

(R≦

τ

_R), then the state machine is in the no talking mode;

if (T>

τ

_L) &

(R≦

τ

_R), then the state machine is in the single talk (local) mode;

if (T≦

τ

_L) &

(R>

τ

_R), then the state machine is in the single talk (remote) mode;

if (T>

τ

_L) &

(R>

τ

_R) &

(T>

R+D1), then the state machine is in the double talk (local wins) mode; and

if (T>

τ

_L) &

(R>

τ

_R) &

(R>

T+D2), then the state machine is in the double talk (remote wins) mode, wherein;

T is an energy for the local audio signals;

R is an energy for the remote audio signals;

τ

_L is a local background noise threshold;

τ

_R is a remote background noise threshold; and

D1 and D2 are specified threshold parameters.

11. The apparatus of claim 9, wherein:

if the state machine is in the no talking mode, then the state machine slowly moves the scalar state variable towards the idle state;

if the state machine is in the single talk (local) mode, then the state machine quickly moves the scalar state variable towards the talk state;

if the state machine is in the single talk (remote) mode, then the state machine quickly moves the scalar state variable towards the listen state;

if the state machine is in the double talk (local wins) mode, then the state machine quickly moves the scalar state variable towards the talk state; and

if the state machine is in the double talk (remote wins) mode, then the state machine quickly moves the scalar state variable towards the listen state.

12. The apparatus of claim 1, wherein:

the scalar state variable is a state variable i;

the state machine comprises a listen state, a talk state, and an idle state;

the state machine further comprises a no talking mode, a single talk (local) mode, a single talk (remote) mode, a double talk (local wins) mode, and a double talk (remote wins) mode;

if (T≦

τ

_L) &

(R≦

τ

_R), then the state machine is in the no talking mode and the state machine slowly moves the scalar state variable i towards the idle state;

if (T>

τ

_L) &

(R≦

τ

_R), then the state machine is in the single talk (local) mode and the state machine quickly moves the scalar state variable i towards the talk state;

if (T≦

τ

_L) &

(R>

τ

_R), then the state machine is in the single talk (remote) mode and the state machine quickly moves the scalar state variable i towards the listen state;

if (T>

τ

_L) &

(R>

τ

_R) &

(T>

R+D1), then the state machine is in the double talk (local wins) mode and the state machine quickly moves the scalar state variable i towards the talk state;

if (T>

τ

_L) &

(R>

τ

_R) &

(R>

T+D2), then the state machine is in the double talk (remote wins) mode and the state machine quickly moves the scalar state variable i towards the listen state, wherein;

T is an energy for the local audio signals;

R is an energy for the remote audio signals;

τ

_L is a local background noise threshold;

τ

_R is a remote background noise threshold; and

D1 and D2 are specified threshold parameters;

when the scaler state variable i is between -j and -k, the state machine is in the listen state and the controller sets the level of transmit attenuation to 0 and the level of receive attenuation to 1, wherein;

-j≦

i≦

j;

j is a specified positive constant; and

k is a specified positive constant less than j;

when the state scalar variable i is between k and j, the state machine is in the talk state and the controller sets the level of transmit attenuation to 1 and the level of receive attenuation to 0; and

when the state scalar variable i is between -k and k, the state machine is in the idle state and the controller sets the level of transmit attenuation to α and

the level of receive attenuation to (1-α

), wherein α

=(i+k) /2k.

13. A computer-implemented process for processing audio signals, comprising the steps of:

(a) generating a scalar state variable with a state machine of a controller;

(b) controlling a level of transmit attenuation and a level of receive attenuation by the controller using the scaler state variable;

(c) attenuating, with a transmit attenuator at the level of transmit attenuation, local audio signals generated with a local microphone for transmission to a remote node; and

(d) attenuating, with a receive attenuator at the level of receive attenuation, remote audio signals received from the remote node for playback at a local speaker.

14. The process of claim 13, wherein step (b) comprises the step of controlling the sum of the level of transmit attenuation and the level of receive attenuation to correspond to unity gain.

15. The process of claim 13, wherein step (b) comprises the step of controlling the levels of transmit and receive attenuation based on:

an energy level for the local audio signals;

an energy level for local background noise;

an energy level for the remote audio signals; and

an energy level for remote background noise.

16. The process of claim 13, wherein step (a) comprises the step of changing the scalar state variable at two or more different rates, where the different rates correspond to different configurations of the local and remote audio signals.

17. The process of claim 13, wherein the state machine comprises a listen state, a talk state, and an idle state.

18. The process of claim 17, wherein:

the scalar state variable is a state variable i;

when the state variable i is between -j and -k, the state machine is in the listen state, wherein;

-j≦

i≦

j;

j is a specified positive constant; and

k is a specified constant less than j;

when the scalar state variable i is between k and j, the state machine is in the talk state; and

when the scalar state variable i is between -k and k, the state machine is in the idle state.

19. The process of claim 18, wherein step (b) comprises the steps off

(1) setting the level of transmit attenuation to 0 and the level of receive attenuation to 1, when the state machine is in the listen state;

(2) setting the level of transmit attenuation to 1 and the level of receive attenuation to 0, when the state machine is in the talk state;

(3) setting the level of transmit attenuation to α and

the level of receive attenuation to (1-α

), when the state machine is in the idle state, wherein 0≦

α

≦

1.

20. The process of claim 19, wherein, when the state machine is in the idle state, α

=(i+k) /2k.

21. The process of claim 13, wherein the state machine comprises a no talking mode, a single talk (local) mode, a single talk (remote) mode, a double talk (local wins) mode, and a double talk (remote wins) mode.

22. The process of claim 21, wherein:

if (T≦

τ

_L) &

(R≦

τ

_R), then the state machine is in the no talking mode;

if (T>

τ

_L) &

(R≦

τ

_R), then the state machine is in the single talk (local) mode;

if (T≦

τ

_L) &

(R>

τ

_R), then the state machine is in the single talk (remote) mode;

if (T>

τ

_L) &

(R>

τ

_R) &

(T>

R+D1), then the state machine is in the double talk (local wins) mode; and

if (T>

τ

_L) &

(R>

τ

_R) &

(R>

T+D2), then the state machine is in the double talk (remote wins) mode, wherein;

T is an energy for the local audio signals;

R is an energy for the remote audio signals;

τ

_L is a local background noise threshold;

τ

_R is a remote background noise threshold; and

D1 and D2 are specified threshold parameters.

23. The process of claim 21, wherein step (a) comprises the steps of:

(1) slowly moving the scalar state variable towards the idle state, if the state machine is in the no talking mode;

(2) quickly moving the scalar state variable towards the talk state, if the state machine is in the single talk (local) mode;

(3) quickly moving the scalar state variable towards the listen state, if the state machine is in the single talk (remote) mode;

(4) quickly moving the scalar state variable towards the talk state, if the state machine is in the double talk (local wins) mode; and

(5) quickly moving the scalar state variable towards the listen state, if the state machine is in the double talk (remote wins) mode.

24. The process of claim 13, wherein:

the state variable is a scalar state variable i,

the state machine comprises a listen state, a talk state, and an idle state;

the state machine further comprises a no talking mode, a single talk (local) mode, a single talk (remote) mode, a double talk (local wins) mode, and a double talk (remote wins) mode;

step (a) comprises the steps of;

(1) if (T≦

τ

_L) &

(R≦

τ

_R), then the state machine is in the no talking mode and the state machine slowly moves the scalar state variable i towards the idle state;

(2) if (T>

τ

_L) &

(R≦

τ

_R), then the state machine is in the single talk (local) mode and the state machine quickly moves the scalar state variable i towards the talk state;

(3) if(T<

τ

_L) &

(R>

τ

_R), then the state machine is in the single talk (remote) mode and the state machine quickly moves the scalar state variable i towards the listen state;

(4) if(T>

τ

_L) &

(R>

τ

_R) &

(T>

R+D1), then the state machine is in the double talk (local wins) mode and the state machine quickly moves the scalar state variable i towards the talk state;

(5) if (T>

τ

_L) &

(R>

τ

_R) &

(R>

T+D2), then the state machine is in the double talk (remote wins) mode and the state machine quickly moves the scalar state variable i towards the listen state, wherein;

T is an energy for the local audio signals;

R is an energy for the remote audio signals;

τ

_L is a local background noise threshold;

τ

_R is a remote background noise threshold; and

D1 and D2 are specified threshold parameters;

step (b) comprises the steps of;

(1) when the scalar state variable i is between -j and -k, the state machine is in the listen state and the controller sets the level of transmit attenuation to 0 and the level of receive attenuation to 1, wherein;

-≦

i≦

j;

j is a specified positive constant; and

k is a specified positive constant less than j;

(2) when the scalar state variable i is between k and j, the state machine is in the talk state and the controller sets the level of transmit attenuation to 1 and the level of receive attenuation to 0; and

(3) when the scalar state variable i is between -k and k, the state machine is in the idle state and the controller sets the level of transmit attenuation to α and

the level of receive attenuation to (1-α

), wherein α

=(i+k) /2k.