Low-latency audio output with variable group delay

Patent metadata

Field	Value
Publication number	US-11438697-B2
Application number	US-201916706287-A
Country	US
Kind code	B2
Filing date	Dec 6, 2019
Priority date	Jun 7, 2019
Publication date	Sep 6, 2022
Grant date	Sep 6, 2022

Abstract

A system may include a digital delta-sigma modulator configured to receive a digital audio input signal and quantize the digital audio input signal into a quantized signal, a filter configured to receive the quantized signal and perform filtering on the quantized signal to generate a filtered quantized signal, the filter having a variable group delay, and a current-mode digital-to-analog converter configured to receive the filtered quantized signal and convert the filtered quantized signal into an equivalent current-mode analog audio signal.

First claim

What is claimed is:

1. A system, comprising:
a digital delta-sigma modulator configured to receive a digital audio input signal and quantize the digital audio input signal into a quantized signal;
a filter configured to receive the quantized signal and perform filtering on the quantized signal to generate a filtered quantized signal, the filter having a variable group delay; and
a current-mode digital-to-analog converter configured to receive the filtered quantized signal and convert the filtered quantized signal into an equivalent current-mode analog audio signal;
wherein:
the variable group delay is selected based on one or more signal characteristics of the quantized signal;
the one or more signal characteristics of the quantized signal comprise a magnitude of the quantized signal; and
selection of the variable group delay is controlled by a control signal independent of the quantized signal.

2. The system of claim 1 , wherein the variable group delay is selected based on whether the digital audio input signal is being used for real-time feedback or real-time feedforward processing.

3. The system of claim 1 , wherein the filter comprises a low-pass out-of-band noise filter.

4. The system of claim 1 , wherein the filter is configured to switch between a first mode in which the filter has a first variable group delay and a second mode in which the filter has a second variable group delay larger than the first variable group delay in a manner that minimizes audible audio artifacts associated with such switching.

5. The system of claim 4 , wherein the variable group delay is selected based on a magnitude of the quantized signal.

6. The system of claim 5 , wherein the first mode is selected if the magnitude is above a predetermined threshold and the second mode is selected if the magnitude is below the predetermined threshold.

7. The system of claim 1 , wherein the current-mode digital-to-analog converter is further configured to drive the equivalent current-mode analog audio signal to a transducer.

8. The system of claim 1 , wherein the filter having a variable group delay is a component of a signal path of an audio integrated circuit (IC).

9. A method, comprising:
receiving a digital audio input signal;
quantizing the digital audio input signal into a quantized signal;
filtering, with a filter having a variable group delay, the quantized signal to generate a filtered quantized signal; and
converting the filtered quantized signal into an equivalent current-mode analog audio signal with a digital-to-analog converter;
wherein:
the variable group delay is selected based on one or more signal characteristics of the quantized signal;
the one or more signal characteristics of the quantized signal comprise a magnitude of the quantized signal; and
selection of the variable group delay is controlled by a control signal independent of the quantized signal.

10. The method of claim 9 , further comprising selecting the variable group delay based on whether the digital audio input signal is being used for real-time feedback or real-time feedforward processing.

11. The method of claim 9 , wherein the filter comprises a low-pass out-of-band noise filter.

12. The method of claim 9 , further comprising switching between a first mode in which the filter has a first variable group delay and a second mode in which the filter has a second variable group delay larger than the first variable group delay in a manner that minimizes audible audio artifacts associated with such switching.

13. The method of claim 12 , wherein the variable group delay is selected based on a magnitude of the quantized signal.

14. The method of claim 13 , wherein the first mode is selected if the magnitude is above a predetermined threshold and the second mode is selected if the magnitude is below the predetermined threshold.

15. The method of claim 9 , further comprising driving, with the current-mode digital-to-analog converter, the equivalent current-mode analog audio signal to a transducer.

16. The method of claim 9 , wherein the filter having a variable group delay is a component of a signal path of an audio integrated circuit (IC).

Assignees

• Cirrus Logic Int Semiconductor Ltd
• Cirrus Logic Inc

Inventors

• Melanson John L
• Shum Wai-Shun
• Yin Leyi

Classifications

• H03M3/50

  Digital/analogue converters using delta-sigma modulation as an intermediate step (digital delta-sigma modulators per se H03M7/3004) · CPC title

• H04R3/04 Primary

  for correcting frequency response · CPC title

• H03M1/742

  using current sources as quantisation value generators · CPC title

• G10L21/0232

  Processing in the frequency domain · CPC title

• H03M1/508 Primary

  the pulse width modulator being of the self-oscillating type · CPC title