Digital compressor for compressing an audio signal

Patent metadata

Field	Value
Publication number	US-9985597-B2
Application number	US-201615082081-A
Country	US
Kind code	B2
Filing date	Mar 28, 2016
Priority date	Jan 30, 2014
Publication date	May 29, 2018
Grant date	May 29, 2018

Abstract

A digital compressor for compressing an input audio signal is presented. The digital compressor comprises a compression gain control for providing a compression gain parameter, and a compression parameter determiner for determining a compression ratio from the compression gain parameter. The compression parameter determiner may be configured to weight the compression gain parameter by a predetermined weight factor to obtain the compression ratio. The digital compressor further comprises an auxiliary signal generator for manipulating the input audio signal in dependence of the compression ratio to obtain a first auxiliary signal, and a combiner unit for combining the first auxiliary signal with the compression gain parameter to obtain a second auxiliary signal, and for combining the input audio signal with the second auxiliary signal to obtain the compressed audio signal.

First claim

What is claimed is:

1. A digital compressor comprising:
an input for receiving an input audio signal;
a processor coupled to the input and configured to:
provide a compression gain parameter;
weight the compression gain parameter by a predetermined weight factor to obtain a compression ratio;
manipulate the input audio signal in dependence of the compression ratio to obtain a first auxiliary signal;
combine the first auxiliary signal with the compression gain parameter to obtain a second auxiliary signal;
combine the input audio signal with the second auxiliary signal to obtain a compressed audio signal;
determine a compression threshold from the compression gain parameter according to the following equation:
T=P max −G ·λ(1+1/ R ),

wherein G denotes the compression gain parameter in a logarithmic scale, wherein λ denotes a tolerance factor, wherein R denotes the compression ratio, wherein P max denotes a maximum magnitude of the input audio signal in a logarithmic scale, and wherein T denotes the compression threshold in a logarithmic scale; and
manipulate the input audio signal to obtain the first auxiliary signal further by comparing the input audio signal with the compression threshold.

2. The digital compressor of claim 1 , wherein the processor is configured to determine the compression ratio according to the following equation:
R=G/K , or R≈G/K,

wherein G denotes the compression gain parameter, wherein K denotes the predetermined weight factor, and wherein R denotes the compression ratio.

3. The digital compressor of claim 1 , wherein the processor is further configured to:
determine an attack filtering time constant from the compression gain parameter according to the following equation:
τ A =A 1 ·G+A 2 ,

wherein G denotes the compression gain parameter in a logarithmic scale, wherein A 1 denotes a first predetermined attack constant, wherein A 2 denotes a second predetermined attack constant, and wherein τ A denotes the attack filtering time constant; and
manipulate the input audio signal to obtain the first auxiliary signal further by filtering the input audio signal in dependence of the attack filtering time constant.

4. The digital compressor of claim 1 , wherein the processor is further configured to:
determine a release filtering time constant from the compression gain parameter according to the following equation:
τ R =B 1· G+B 2 ,

wherein G denotes the compression gain parameter in a logarithmic scale, wherein B 1 denotes a first predetermined release constant, wherein B 2 denotes a second predetermined release constant, and wherein τ R denotes the release filtering time constant; and
manipulate the input audio signal to obtain the first auxiliary signal further by filtering the input audio signal in dependence of the release filtering time constant.

5. The digital compressor of claim 1 , wherein the processor is further configured to filter the input audio signal by a digital filter, the digital filter comprising a frequency transfer function having a magnitude over frequency, wherein the magnitude is formed by an equal loudness curve of a human ear.

6. The digital compressor of claim 1 , wherein the processor is further configured to filter the input audio signal by applying a digital low-pass filter, the digital low-pass filter comprising a filter step response in time domain.

7. The digital compressor of claim 6 , wherein the digital low-pass filter is configured to filter the input audio signal according to the following equations:

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Assignees

• Huawei Tech Co Ltd

Inventors

• Grosche Peter
• Lang Yue
• Zhang Qing

Classifications

• H03G7/007

  of digital or coded signals · CPC title

• H03G7/002 Primary

  in untuned or low-frequency amplifiers, e.g. audio amplifiers (H03G7/007, H03G7/001, H03G7/008, H03G7/02, H03G7/06 take precedence) · CPC title

• H03G9/18

  for tone control and volume expansion or compression · CPC title