System and method for gain control of audio sample packets

• US 20030161276A1
• Filed: 08/14/2002
• Published: 08/28/2003
• Est. Priority Date: 02/25/2002
• Status: Active Grant

• Current Assignee: Sonexis Technology, Inc. (Compunetix, Inc.)
• Original Assignee: Sixenos, Inc. (Compunetix, Inc.)
• Inventors: Lundberg, Keith M., Reilly, Paul W.
• Granted Patent: US 7,145,883 B2
• Time in Patent Office: Days
• US Class Current: 370/267
• CPC Class Codes: H04M 3/56 Arrangements for connecting several subscribers to a common circuit, i.e. affording conference facilities video conference systems H04N7/15
• 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

Determining gain factors for a sequential multiplicity of audio sample packets by first determining a comparison peak value for a present such packet by multiplying a highest sample value by a previously predetermined gain factor, determining a hysteretic peak value for the present peak from the comparison peak value and a hysteretic peak value from a previously processed packet and determining a gain factor for use with subsequent packets.

Claims

1. A method for determining gain factors for a sequential multiplicity of audio sample packets, based upon sequentially processing each packet as a present packet, comprising:

determining a comparison peak value for a present packet by multiplying a highest sample value from said present packet by a previously determined gain factor;

determining a present packet hysteretic peak value from said comparison peak value and a previously determined hysteretic peak value from a previously processed packet; and

determining a new gain factor, for use with one or more subsequently processed packets, by periodically comparing present packet hysteretic peak values against predetermined minimum and maximum range values.

2. The method of claim 1, wherein said step of determining a present packet hysteretic peak value includes adding a fraction of said comparison peak value to a complementary fraction of the hysteretic peak value determined for a last-processed sequential packet.

3. The method of claim 1, wherein said step of determining a new gain factor is performed once for every predetermined number of packets.

4. The method of claim 1, wherein said step of determining a new gain factor includes detecting for silence by comparing present packet hysteretic peak values against a silence threshold value.

5. The method of claim 4, wherein said step of determining a new gain factor includes using said previously determined gain factor as said new gain factor if the compared hysteretic peak value is between said predetermined minimum and maximum range values or below said silence threshold value, and adjusting said previously determined gain factor in response to said step of comparing to determine said new gain factor, if said compared hysteretic peak value is neither between said predetermined minimum and maximum range values nor below said silence threshold value.

6. The method of claim 1, further comprising adjusting said present packet hysteretic peak value in response to said step of adjusting said previously determined gain factor for causing said present packet hysteretic peak value to be based upon said new gain factor.

7. The method of claim 1, further comprising:

detecting any presence of clipping from said comparison peak value; and

determining a new gain factor in response to said presence of clipping by lowering said previously determined gain factor by a predetermined amount.

8. The method of claim 1, wherein said step of determining a comparison peak includes multiplying all sample values in said present packet by said previously determined gain factor.

9. A digital processor for determining gain factors for a sequential multiplicity of audio sample packets, based upon sequentially processing each packet as a present packet, comprising:

first processing means for determining a comparison peak value for a present packet by multiplying a highest sample value from said present packet by a previously determined gain factor;

second processing means for determining a present packet hysteretic peak value from said comparison peak value and a hysteretic peak value from a previously processed packet;

third processing means for periodically comparing present packet hysteretic peak values, against predetermined range values;

fourth processing means for determining a new gain factor, for use with one or more subsequently processed packets, based upon said previously determined gain factor and in response to said third processing means for comparing; and

fifth processing means for adjusting said present packet hysteretic peak value in response to said fourth processing means, for causing said present packet hysteretic peak value to be based upon said new gain factor.

10. The digital processor of claim 9, wherein said third processing means is adapted for comparing present packet hysteretic peak values against predetermined minimum and maximum range values and against a lower, silence threshold value;

and

further wherein said fourth processing means for determining a new gain factor includes sixth processing means for using said previously determined gain factor as said new gain factor if said hysteretic peak value is either between said predetermined minimum and maximum range values or below said lower, silence threshold value.

11. The digital processor of claim 10, further comprising seventh processing means for detecting any presence of clipping from said comparison peak value determined by said first processing means, wherein said fourth processing means for determining a new gain factor includes eighth processing means for determining said new gain factor in response to said presence of clipping by lowering said previously determined gain factor by a predetermined amount.

12. The digital processor of claim 11, wherein said second processing means for determining a present packet hysteretic peak value includes ninth processing means for adding a fraction of said comparison peak value to a complementary fraction of the hysteretic peak value determined for a previously processed packet.

13. The digital processor of claim 12, wherein said first processing means for determining a comparison peak value includes tenth processing means for multiplying all sample values in said present packet by said previously determined gain factor.

14. The digital processor of claim 13, wherein each of said processing means is stored as computer instructions in computer readable media.

15. A telephone conferencing system for processing separate sequences of audio input packets from a multiplicity of connections based upon sequentially processing each packet as a present packet, comprising;

a first determining process adapted for determining a comparison peak value for each packet by multiplying a highest sample value from a present packet by a previously determined, connection-specific gain factor;

a second determining process adapted for determining a present packet hysteretic peak value from said comparison peak value and a previously determined hysteretic peak value of a last-processed connection-specific packet;

a comparing process adapted for periodically comparing present packet hysteretic peak values against predetermined minimum and maximum range values and against a silence threshold value;

a first adjusting process responsive to said comparing process, and adapted for adjusting said previously determined connection-specific gain factor to determine a new connection-specific gain factor for use with one or more subsequently processed connection-specific packets, if a compared present packet hysteretic peak value is neither between said predetermined minimum and maximum range values nor below said silence threshold value; and

a second adjusting process adapted for adjusting said present packet hysteretic peak value, in response to said first adjusting process, for causing said present packet hysteretic peak value to be based upon said new gain factor.

16. The system of claim 15, wherein said first adjusting process is adapted to use said previously determined connection-specific gain factor as said new gain factor if a compared present packet hysteretic peak value is between said predetermined minimum and maximum range values or below said silence threshold value.

17. The system of claim 16, further comprising a detecting process adapted for detecting any presence of clipping from said comparison peak value, and a third adjusting process adapted to lower said previously determined connection-specific gain factor by a predetermined amount in response to said presence of clipping, to determine said new connection-specific gain factor.

18. The system of claim 17, wherein said second determining process for determining a present packet hysteretic peak value includes an adding process adapted for adding a fraction of said comparison peak value to a complementary fraction of the hysteretic peak value determined for a previously processed, connection specific packet.

19. The system of claim 15, wherein said first determining process for determining a comparison peak value includes a multiplying process adapted for multiplying all sample values in said present packet by said previously determined gain factor.

20. The system of claim 15, wherein said comparing process is adapted to compare a present packet hysteretic peak value once every predetermined number of sequentially processed audio input packets.