# US 11,308,976 B2 · Post-processing gains for signal enhancement

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- Number: US 11,308,976 B2
- Document ID: US11308976B2
- Status: Granted
- Kind: B2
- Application number: 17/156,485
- Filed: 2021-01-22
- Published: 2021-07-15
- Granted: 2022-04-19
- Earliest claimed: 2012-03-23
- Assignees: Dolby Laboratories Licensing Corporation
- Applicants: Dolby Laboratories Licensing Corporation
- Inventors: Xuejing Sun; Glenn N. Dickins
- Web page: https://patentgrep.com/patent/US11308976B2

## CPC

- G10L 21/0364: for improving intelligibility
- G10K 11/16: Methods or devices for protecting against, or for damping, noise or other acoustic waves in general (G10K11/36 takes precedence)
- G10L 21/0224: Processing in the time domain
- G10L 21/0316: by changing the amplitude
- G10L 21/034: Automatic adjustment
- G10L 25/78: Detection of presence or absence of voice signals (switching of direction of transmission by voice frequency in two-way loud-speaking telephone systems H04M9/10)
- H03G 3/301: {the gain being continuously variable}
- H03G 3/32: the control being dependent upon ambient noise level or sound level
- G10L: SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; SPEECH OR AUDIO CODING OR DECODING
- G10K: SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
- H03G: CONTROL OF AMPLIFICATION

## Abstract

A method, an apparatus, and logic to post-process raw gains determined by input processing to generate post-processed gains, comprising using one or both of delta gain smoothing and decision-directed gain smoothing. The delta gain smoothing comprises applying a smoothing filter to the raw gain with a smoothing factor that depends on the gain delta: the absolute value of the difference between the raw gain for the current frame and the post-processed gain for a previous frame. The decision-directed gain smoothing comprises converting the raw gain to a signal-to-noise ratio, applying a smoothing filter with a smoothing factor to the signal-to-noise ratio to calculate a smoothed signal-to-noise ratio, and converting the smoothed signal-to-noise ratio to determine the second smoothed gain, with smoothing factor possibly dependent on the gain delta.

## Claims

### Claim 1

An audio processing apparatus, comprising:
at least one processor; and
at least one memory storing a computer program;
in which the at least one memory with the computer program is configured with the at least one processor to cause the audio processing apparatus to at least:
receive at least one audio signal,
analyze the at least one audio signal to determine a raw dynamic range control (DRC) gain, wherein the raw DRC gain depends on a level of the audio signal,
select a raw DRC gain smoothing factor from a plurality of raw DRC gain smoothing factors, wherein the plurality of raw DRC gain smoothing factors corresponds to a plurality of raw DRC gain smoothing time durations, and wherein a first raw DRC gain smoothing factor is selected if the raw DRC gain is greater than a previous smoothed DRC gain, and wherein a second raw DRC gain smoothing factor is selected if the raw DRC gain is less than the previous smoothed DRC gain;
determine a current smoothed DRC gain from the raw DRC gain, the previous smoothed DRC gain, and the selected raw DRC gain smoothing factor; and
control a dynamic range of the audio signal by applying the current smoothed DRC gain to the audio signal.

### Claim 2 (depends on 1)

The audio processing apparatus of claim 1, wherein the audio signal comprises a plurality of frames.

### Claim 3 (depends on 2)

The audio processing apparatus of claim 2, wherein the raw DRC gain corresponds to a current frame of the plurality of frames of the audio signal.

### Claim 4 (depends on 2)

The audio processing apparatus of claim 2, wherein the current smoothed DRC gain corresponds to a current frame of the plurality of frames of the audio signal.

### Claim 5 (depends on 2)

The audio processing apparatus of claim 2, wherein the previous smoothed DRC gain corresponds to a smoothed DRC gain of a previous frame of the plurality of frames of the audio signal.

### Claim 6 (depends on 5)

The audio processing apparatus of claim 5, wherein the previous frame of the plurality of frames of the audio signal immediately precedes a current frame of the plurality of frames of the audio signal.

### Claim 7 (depends on 2)

The audio processing apparatus of claim 2, wherein a current frame of the plurality of frames of the audio signal is transformed into a transform domain, the audio signal is analyzed in the transform domain, and the current smoothed DRC gain is applied to the audio signal in the transform domain.

### Claim 8

A program storage device readable by a machine, tangibly embodying a program of instructions executable by one or more processors of the machine for causing to perform operations, said operations comprising:
receiving at least one audio signal,
analyzing the at least one audio signal to determine a raw dynamic range control (DRC) gain, wherein the raw DRC gain depends on a level of the audio signal;
selecting a raw DRC gain smoothing factor from a plurality of raw DRC gain smoothing factors, wherein the plurality of raw DRC gain smoothing factors corresponds to a plurality of raw DRC gain smoothing time durations, and wherein a first raw DRC gain smoothing factor is selected if the raw DRC gain is greater than a previous smoothed DRC gain, and wherein a second raw DRC gain smoothing factor is selected if the raw DRC gain is less than the previous smoothed DRC gain;
determining a current smoothed DRC gain from the raw DRC gain, the previous smoothed DRC gain, and the selected raw DRC gain smoothing factor; and
controlling a dynamic range of the audio signal by applying the current smoothed DRC gain to the audio signal.

### Claim 9

A method, performed by an audio processing apparatus, the method comprising:
receiving at least one audio signal,
analyzing the at least one audio signal to determine a raw dynamic range control (DRC) gain, wherein the raw DRC gain depends on a level of the audio signal;
selecting a raw DRC gain smoothing factor, from a plurality of raw DRC gain smoothing factors, wherein the plurality of raw DRC gain smoothing factors corresponds to a plurality of raw DRC gain smoothing time durations, and wherein a first raw DRC gain smoothing factor is selected if the raw DRC gain is greater than a previous smoothed DRC gain, and wherein a second raw DRC gain smoothing factor is selected if the raw DRC gain is less than the previous smoothed DRC gain;
determining a current smoothed DRC gain from the raw DRC gain, the previous smoothed DRC gain, and the selected raw DRC gain smoothing factor; and
controlling a dynamic range of the audio signal by applying the current smoothed DRC gain to the audio signal.