Signal clipping compensation

Patent metadata

Field	Value
Publication number	US-9679578-B1
Application number	US-201615253142-A
Country	US
Kind code	B1
Filing date	Aug 31, 2016
Priority date	Aug 31, 2016
Publication date	Jun 13, 2017
Grant date	Jun 13, 2017

Abstract

A method may include determining that values of a plurality of samples of a digital audio signal that are stored in an input buffer exceed a clipping threshold value. The method may further include identifying the plurality of samples that exceed the clipping threshold value as potentially clipped samples of the digital audio signal. In addition, the method may include generating, based on identification of the potentially clipped samples, attenuated samples by uniformly applying a fixed attenuation factor to the potentially clipped samples and to every sample of the digital audio signal included in the input buffer that follows the potentially clipped samples. Further, the method may include generating a plurality of modified attenuated samples by applying interpolation to the attenuated samples that correspond to the potentially clipped samples. The method may also include outputting the attenuated samples and the modified attenuated samples as a modified digital audio signal.

First claim

What is claimed is:

1. A computer-implemented method to compensate for signal clipping, the method comprising:
determining that values of a plurality of samples of a digital audio signal that are stored in an input buffer exceed a clipping threshold value, wherein the clipping threshold value is related to clipping of the digital audio signal and is based on an amplitude limit of a system configured to perform operations with respect to the digital audio signal;
identifying the plurality of samples that exceed the clipping threshold value as potentially clipped samples of the digital audio signal;
generating, based on identification of the potentially clipped samples, attenuated samples by uniformly applying a fixed attenuation factor to the potentially clipped samples and to every sample of the digital audio signal that is included in the input buffer and that follows the potentially clipped samples, wherein the fixed attenuation factor is based on one or more of: a resolution of the system, a headroom of the system, a dynamic range of the system, and potential signal loss and wherein uniformly applying the fixed attenuation factor attenuates the value of every sample that is attenuated by a same multiplication factor that corresponds to the fixed attenuation factor;
generating a plurality of modified attenuated samples by applying interpolation to the attenuated samples that correspond to the potentially clipped samples; and
outputting the attenuated samples and the modified attenuated samples as a modified digital audio signal.

2. The method of claim 1 , wherein generating the attenuated samples based on identification of the potentially clipped samples comprises:
flagging the samples included in the input buffer for attenuation based on the samples included in the input buffer including the potentially clipped samples; and
generating the attenuated samples with respect to the flagged samples.

3. The method of claim 2 , wherein:
the samples included in the input buffer are included in one or more frames of the digital audio signal; and
flagging the samples includes flagging the one or more frames.

4. The method of claim 1 , further comprising using the modified attenuated samples with respect to a telephone captioning system.

5. The method of claim 1 , wherein applying the interpolation includes performing one or more of the following interpolation techniques: a polynomial interpolation technique, and a spline interpolation technique.

6. The method of claim 1 , further comprising attenuating an other set of samples that are included in the input buffer after the attenuated samples and the modified attenuated samples are output from the input buffer, wherein the other set of samples does not include any identified potentially clipped samples and are attenuated based on the attenuated samples and the modified attenuated samples being previously stored in the input buffer and being attenuated.

7. The method of claim 6 , wherein the fixed attenuation factor is a first attenuation factor and wherein attenuating the other set of samples includes applying a second attenuation factor that is smaller than the first attenuation factor to the other set of samples such that the other set of samples are attenuated less than the attenuated samples and the modified attenuated samples.

8. The method of claim 1 , further comprising uniformly applying the fixed attenuation factor to every sample of the digital audio signal that is included in the input buffer.

9. At least one non-transitory computer readable media configured to store one or more instructions that when executed by at least one computing system cause the at least one computing system to perform the method of claim 1 .

10. A method comprising:
determining that values of a plurality of samples of a first frame of a digital audio signal that is stored in an input buffer exceed a clipping threshold value, wherein the clipping threshold value is related to clipping of the digital audio signal and is based on an amplitude limit of a system configured to perform operations with respect to the digital audio signal;
identifying the plurality of samples that exceed the clipping threshold value as potentially clipped samples of the digital audio signal;
generating, based on identification of the potentially clipped samples, attenuated samples by uniformly applying a first fixed attenuation factor to the potentially clipped samples and to every sample of the first frame that is included in the input buffer and that follows the potentially clipped samples, wherein the fixed attenuation factor is based on one or more of: a resolution of the system, a headroom of the system, a dynamic range of the system, and potential signal loss and wherein uniformly applying the fixed attenuation factor attenuates the value of every sample that is attenuated by a same multiplication factor that corresponds to the fixed attenuation factor;
generating a plurality of modified attenuated samples by applying interpolation to the attenuated samples that correspond to the potentially clipped samples;
outputting the attenuated samples and the modified attenuated samples as a modified first frame; and
attenuating, by a second fixed attenuation factor that is smaller than the first fixed attenuation factor, every sample of a second frame of the digital signal that is stored in the input buffer after the modified first frame is output from the input buffer, wherein the second frame does not include any identified potentially clipped samples and is attenuated based on the modified first frame being previously stored in the input buffer and having attenuated samples.

11. The method of claim 10 , wherein generating the attenuated samples based on identification of the potentially clipped samples comprises:
flagging the samples included in the input buffer for attenuation based on the samples included in the input buffer including the potentially clipped samples; and
generating the attenuated samples with respect to the flagged samples.

12. The method of claim 11 , wherein flagging the samples includes flagging the first frame.

13. The method of claim 10 , further comprising using the modified attenuated samples with respect to a telephone captioning system.

14. The method of claim 10 , wherein applying the interpolation includes performing one or more of the following interpolation techniques: a polynomial interpolation technique, and a spline interpolation technique.

15. The method of claim 10 , further comprising uniformly applying the fixed attenuation factor to every sample of the digital audio signal that is included in the input buffer.

16. At least one non-transitory computer readable media is configured to store one or more instructions that when executed by at least one computing system cause the at least one system to perform the method of claim 10 .

17. A system comprising:
a processor; and
at least one non-transitory computer readable media communicatively coupled to the processor and configured to store one or more instructions that when executed by the processor causes a computing system to perform operations, the operations comprising:
determining that values of a plurality of samples of a digital audio signal that are stored in an input buffer exceed a clipping threshold value;
identifying the plurality of samples that exceed the clipping threshold value as potentially clipped samples of the digital audio signal;
generating, based on identification of the potentially clipped samples, attenuated samples by uniformly applying a fixed atte

Assignees

• Sorenson Ip Holdings Llc

Inventors

• Bullough Jeffrey C

Classifications

• H04L27/2623

  Reduction thereof by clipping · CPC title

• G10L21/0332 Primary

  involving modification of waveforms · CPC title

• H03G11/008

  of digital or coded signals · CPC title

• H03M1/0607

  Offset or drift compensation (removal of offset already present on the analogue input signal H03M1/1295) · CPC title

• H03G7/007

  of digital or coded signals · CPC title