Techniques for distortion reducing multi-band compressor with timbre preservation

Patent metadata

Field	Value
Publication number	US-9419577-B2
Application number	US-201514732271-A
Country	US
Kind code	B2
Filing date	Jun 5, 2015
Priority date	Mar 18, 2010
Publication date	Aug 16, 2016
Grant date	Aug 16, 2016

Abstract

Distortion reducing multi-band compressor with timbre preservation is provided. Timbre preservation is achieved by determining a time-varying threshold in each of a plurality frequency bands as a function of a respective fixed threshold for the frequency band and, at least in part, an audio signal level and a fixed threshold outside such frequency band. If a particular frequency band receives significant gain reduction due to being above or approaching its fixed threshold, then a time-varying threshold of one or more other frequency bands are also decreased to receive some gain reduction. In a specific embodiment, time-varying thresholds can be computed from an average difference of the audio input signal in each frequency band and its respective fixed threshold.

First claim

What is claimed is:

1. An apparatus comprising:
a multi-band filterbank configured to split an audio signal for a plurality of frequency bands;
compression function element dedicated to a frequency band of the plurality of frequency bands;
a timbre preservation element coupled to the compression function element, the timbre preservation element configured to provide a time-varying threshold for the frequency band; and
at least one audio transducer configured to audibly present an audio signal outputted from the compression function element,
wherein the time-varying threshold for the frequency band is determined by levels of the audio signal from neighboring frequency bands but not all of the plurality of frequency bands.

2. The apparatus of claim 1 wherein the time-varying threshold for the frequency band is further determined by a plurality of fixed thresholds from the neighboring frequency bands.

3. The apparatus of claim 1 wherein the levels are estimated power levels.

4. An apparatus comprising:
a multi-band filterbank configured to split an audio signal for a plurality of frequency bands;
compression function element dedicated to a frequency band of the plurality of frequency bands;
a timbre preservation element coupled to the compression function element, the timbre preservation element configured to provide a time-varying threshold for the frequency band; and
at least one audio transducer configured to audibly present an audio signal outputted from the compression function element,
wherein the time-varying threshold for the frequency band is determined by at least one level of the audio signal outside the frequency band but not all of the plurality of frequency bands.

5. The apparatus of claim 4 wherein the time-varying threshold for a first frequency band is further determined by a fixed threshold from a neighboring band.

6. The apparatus of claim 4 wherein the at least one level is estimated power levels.

Assignees

• Dolby Laboratories Licensing Corp

Inventors

• Seefeldt Alan J

Classifications

• H03G9/025 Primary

  frequency-dependent volume compression or expansion, e.g. multiple-band systems (H03G9/10, H03G9/18 take precedence) · CPC title

• H03G9/005 Primary

  of digital or coded signals · CPC title

• H04R2430/03

  Synergistic effects of band splitting and sub-band processing · CPC title

• H03G9/18

  for tone control and volume expansion or compression · CPC title

• H04R3/04

  for correcting frequency response · CPC title