Automatic level control for psychoacoustic bass enhancement

• US 10,382,857 B1
• Filed: 03/28/2018
• Issued: 08/13/2019
• Est. Priority Date: 03/28/2018
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Khanal, Sarthak, Breitschaedel, Hannes, Iyengar, Vasu
• Primary Examiner(s): Patel, Yogeshkumar
• Application Number:
  US15/939,224
• Time in Patent Office: 503 Days
• Field of Search: 381 98, 381104, 381107, 381119, 381102, 381106, 381 59
• CPC Class Codes: H04R 1/22 for obtaining desired frequency characteristic only circuit for combining transducers having different responses H04R3/00; for hearing aids H04R25/407
• CPC Class Codes: H04R 2430/01 Aspects of volume control, not necessarily automatic, in sound systems
• CPC Class Codes: H04R 2430/03 Synergistic effects of band splitting and sub-band processing
• CPC Class Codes: H04R 3/04 for correcting frequency response
• CPC Class Codes: H04R 5/04 Circuit arrangements, e.g. for selective connection of amplifier inputs/outputs to loudspeakers, for loudspeaker detection, or for adaptation of settings to personal preferences or hearing impairments combinations of amplifiers H03F3/68; stereophonic systems H04S

Abstract

An audio electronics system operates on audio data. A low-pass or bandpass filter produces first data from audio data. A level detector produces a time-varying first gain. The first gain is based on a time-varying level of the first data. A harmonics generator receives, as input, the first data adjusted by an inverse of the first gain. The harmonics generator produces second data, as harmonics of the input. A multiplier outputs the second data adjusted by the first gain. Other aspects are also described and claimed.

Claims

1. An audio electronics system comprising:

a first summer to add first channel audio data and second channel audio data to produce audio data;

a first high pass filter to receive the first channel audio data and produce high pass filtered first channel audio data;

a second high pass filter to receive the second channel audio data and produce high pass filtered second channel audio data;

a low pass or bandpass filter to produce first data from the audio data;

a level detector to produce a time-varying first gain based on a time-varying level of the first data;

a harmonics generator to receive as input the first data that has been adjusted by an inverse of the first gain, and to produce second data as harmonics of the input;

a first multiplier to output the second data adjusted by the first gain;

a second summer to add i) the high pass filtered first channel audio data and ii) the second data adjusted by the first gain, to produce psychoacoustic bass enhanced first channel audio data; and

a third summer to add i) the high pass filtered second channel audio data and ii) the second data adjusted by the first gain, to produce psychoacoustic bass enhanced second channel audio data.

2. The audio electronics system of claim 1, further comprising:

a clipper to receive as input the first data adjusted by the inverse of the first gain, and whose output is provided as the input to the harmonics generator.

3. The audio electronics system of claim 1, further comprising:

a harmonics shaping bandpass filter to adjust the second data.

4. The audio electronics system of claim 1, further comprising:

a second level detector to produce a time-varying second gain based on a time-varying level of the second data, wherein the multiplier to output the second data adjusted by the first gain comprises the multiplier to output the second data adjusted by the first gain and by an inverse of the second gain.

5. The audio electronics system of claim 1, wherein:

the level detector comprises a peak follower, an envelope detector or an RMS (root mean square) detector; and

the harmonics generator comprises a hyperbolic tangent or an exponential.

6. A tangible, non-transitory, computer-readable media having instructions thereupon which, when executed by a processor, cause the processor to perform a method comprising:

adding first channel audio data and second channel audio data to produce audio data;

high pass filtering the first channel audio data to produce high pass filtered first channel audio data;

high pass filtering the second channel audio data to produce high pass filtered second channel audio data;

low-pass or band pass filtering the audio data to produce first data;

generating a time-varying first gain based on a time-varying level of the first data;

multiplying the first data by an inverse of the first gain, or dividing by the first gain, to produce level controlled first data;

generating harmonics of the level controlled first data, as second data;

multiplying the second data by the first gain, to produce level controlled second data;

multiplying a harmonics gain value by the level controlled second data to produce third data;

adding the high pass filtered first channel audio data and the third data to produce psychoacoustic bass enhanced first channel audio data; and

adding the high pass filtered second channel audio data and the third data to produce psychoacoustic bass enhanced second channel audio data.

7. The computer-readable media of claim 6, wherein the method further comprises:

clipping a peak from the level controlled first data.

8. The computer-readable media of claim 6, wherein the method further comprises:

bandpass filtering the level controlled second data; and

adjusting a level of each band of the band pass filtered level controlled second data.

9. The computer-readable media of claim 6, wherein the method further comprises:

generating a time-varying second gain value based on a time-varying level of the second data, wherein the multiplying the second data by the first gain to produce the level controlled second data comprises multiplying the second data by the first gain and by an inverse of the second gain, to produce the level controlled second data.

10. A method of processing audio data, performed by a processor-based system, the method comprising:

combining first channel audio data and second channel audio data to produce audio data;

filtering the first channel audio data, with a high pass filter, to produce high pass filtered first channel audio data;

filtering the second channel audio data, with a high pass filter, to produce high pass filtered second channel audio data;

filtering the audio data, with a low-pass or band pass filter, to produce first data;

determining a time-varying first gain based on a time-varying level of the first data;

determining level controlled first data as the first data multiplied by an inverse of the first gain or divided by the first gain;

determining second data as harmonics of the level controlled first data;

determining level controlled second data as the second data multiplied by the first gain;

determining third data as a harmonics gain value multiplied by the level controlled second data;

determining psychoacoustic bass enhanced first channel audio data as the high pass filtered first channel audio data added to the third data; and

determining psychoacoustic bass enhanced second channel audio data as the high pass filtered second channel audio data added to the third data.

11. The method of claim 10, further comprising:

removing a peak from the level controlled first data.

12. The method of claim 10, further comprising:

shaping the second data with a bandpass filter.

13. The method of claim 10, further comprising:

determining a time-varying second gain based on a time-varying level of the second data, wherein the determining the level controlled second data as the second data multiplied by the first gain comprises determining the level controlled second data as the second data multiplied by the first gain and divided by the second gain.

14. The method of claim 10, wherein:

the determining the time-varying first gain comprises producing an output of a peak follower, an envelope detector or an RMS (root mean square) detector; and

the determining the second data as the harmonics of the level controlled first data comprises determining a hyperbolic tangent or an exponential of the level controlled first data.