# US 10,873,811 B1 · Low-latency audio output with variable group delay > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,873,811 B1 - Document ID: US10873811B1 - Status: Granted - Kind: B1 - Application number: 16/937,211 - Filed: 2020-07-23 - Published: 2020-12-10 - Granted: 2020-12-22 - Earliest claimed: 2019-06-07 - Assignees: Cirrus Logic, Inc. - Applicants: Cirrus Logic International Semiconductor Ltd. - Inventors: John L. Melanson - Web page: https://patentgrep.com/patent/US10873811B1 ## CPC - H04R 3/04: for correcting frequency response - G10L 21/0232: Processing in the frequency domain - H03F 3/181: Low-frequency amplifiers, e.g. audio preamplifiers - H04S 1/007: {in which the audio signals are in digital form (data reduction aspects thereof based on psychoacoustics G10L19/02)} - H03F 2200/03: the amplifier being designed for audio applications - H03F 2200/165: A filter circuit coupled to the input of an amplifier - H04S 2400/09: Electronic reduction of distortion of stereophonic sound systems - H04R: LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; ELECTRIC HEARING AIDS; PUBLIC ADDRESS SYSTEMS (producing sounds with frequency not determined by supply frequency G10K) - G10L: SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; SPEECH OR AUDIO CODING OR DECODING - H03F: AMPLIFIERS - H04S: STEREOPHONIC SYSTEMS ## Abstract A system may include an input configured to receive a digital audio input signal having at least four and fewer than 65,000 quantization levels and sampled at at least 500 kilohertz, a low-pass filter configured to receive the digital audio input signal and perform filtering on the digital audio input signal to generate a filtered digital audio input signal having a bandwidth of between approximately 100 hertz and 10 kilohertz, a digital-to-analog converter configured to receive the filtered digital audio input signal and convert the filtered digital audio input signal into an equivalent analog audio input signal, and a driver configured to receive the equivalent analog audio input signal and drive an analog audio output signal to a transducer, wherein a group delay from the input to an output of the driver is less than 50 microseconds. ## Claims ### Claim 1 A system, comprising: an input configured to receive a digital audio input signal having at least four and fewer than 65,000 quantization levels and sampled at at least 500 kilohertz; a low-pass filter configured to receive the digital audio input signal and perform filtering on the digital audio input signal to generate a filtered digital audio input signal; a digital-to-analog converter configured to receive the filtered digital audio input signal and convert the filtered digital audio input signal into an equivalent analog audio input signal; and a driver configured to receive the equivalent analog audio input signal and drive an analog audio output signal to a transducer; wherein a group delay from the input to an output of the driver is less than 50 microseconds. ### Claim 2 (depends on 1) The system of claim 1, wherein the low-pass filter has a variable group delay. ### Claim 3 (depends on 2) The system of claim 2, wherein the variable group delay is selected based on one or more signal characteristics of the digital audio input signal. ### Claim 4 (depends on 3) The system of claim 3, wherein the one or more signal characteristics of the digital audio input signal comprise a magnitude of the digital audio input signal. ### Claim 5 (depends on 2) The system of claim 2, 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. ### Claim 6 (depends on 1) 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 in a manner that minimizes audible audio artifacts associated with such switching. ### Claim 7 (depends on 1) The system of claim 1, wherein a group delay from the input to an output of the driver is less than 15 microseconds. ### Claim 8 A method, comprising: receiving a digital audio input signal having at least four and fewer than 65,000 quantization levels and sampled at at least 500 kilohertz; filtering the digital audio input signal with a low-pass filter to generate a filtered digital audio input signal; converting the filtered digital audio input signal into an equivalent analog audio input signal with a digital-to-analog converter; and driving an analog audio output signal to a transducer based on the equivalent analog audio input signal; wherein a group delay from the input to an output of the driver is less than 50 microseconds. ### Claim 9 (depends on 8) The method of claim 8, wherein the low-pass filter has a variable group delay. ### Claim 10 (depends on 9) The method of claim 9, further comprising selecting the variable group delay based on one or more signal characteristics of the digital audio input signal. ### Claim 11 (depends on 10) The method of claim 10, wherein the one or more signal characteristics of the digital audio input signal comprise a magnitude of the digital audio input signal. ### Claim 12 (depends on 9) 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. ### Claim 13 (depends on 8) The method of claim 8, 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 in a manner that minimizes audible audio artifacts associated with such switching. ### Claim 14 (depends on 8) The method of claim 8, wherein a group delay from the input to an output of the driver is less than 15 microseconds.