Low-latency audio output with variable group delay

Patent metadata

Field	Value
Publication number	US-2020389727-A1
Application number	US-201916706287-A
Country	US
Kind code	A1
Filing date	Dec 6, 2019
Priority date	Jun 7, 2019
Publication date	Dec 10, 2020
Grant date	—

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.

2 . The system of claim 1 , wherein the variable group delay is selected based on one or more signal characteristics of the quantized signal.

3 . The system of claim 2 , wherein the one or more signal characteristics of the quantized signal comprise a magnitude of the quantized signal.

4 . 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.

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

6 . 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.

7 . The system of claim 6 , wherein the variable group delay is selected based on a magnitude of the quantized signal.

8 . The system of claim 7 , 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.

9 . 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.

10 . 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.

11 . The method of claim 10 , wherein the variable group delay is selected based on one or more signal characteristics of the quantized signal.

12 . The method of claim 11 , wherein the one or more signal characteristics of the quantized signal comprise a magnitude of the quantized signal.

13 . The method of claim 10 , 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.

14 . The method of claim 10 , wherein the filter comprises a low-pass out-of-band noise filter.

15 . The method of claim 10 , 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.

16 . The method of claim 15 , wherein the variable group delay is selected based on a magnitude of the quantized signal.

17 . The method of claim 16 , 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.

18 . The method of claim 10 , further comprising driving, with the current-mode digital-to-analog converter, the equivalent current-mode analog audio signal to a transducer.

Assignees

• Cirrus Logic Int Semiconductor Ltd

Inventors

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

Classifications

• H04R3/04 Primary

  for correcting frequency response · CPC title

• H03M1/508 Primary

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

• H03M1/742

  using current sources as quantisation value generators · CPC title

• H03M3/50

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

• G10L21/0232

  Processing in the frequency domain · CPC title