# US 12,191,834 B2 · Method and unit for performing dynamic range control

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- Number: US 12,191,834 B2
- Document ID: US12191834B2
- Status: Granted
- Kind: B2
- Application number: 17/921,279
- Filed: 2021-05-17
- Published: 2023-06-22
- Granted: 2025-01-07
- Earliest claimed: 2020-05-20
- Assignees: Dolby International AB
- Applicants: Dolby International AB
- Inventors: Stanislaw Gorlow; Robin Thesing
- Web page: https://patentgrep.com/patent/US12191834B2

## CPC

- G10L 21/0316: by changing the amplitude
- H03G 9/025: {frequency-dependent volume compression or expansion, e.g. multiple-band systems (H03G9/10, H03G9/18 take precedence)}
- G10L 21/0364: for improving intelligibility
- H03G 7/007: {of digital or coded signals}
- H03G 9/005: {of digital or coded signals}
- G10L 19/008: Multichannel audio signal coding or decoding using interchannel correlation to reduce redundancy, e.g. joint-stereo, intensity-coding or matrixing
- G10L: SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; SPEECH OR AUDIO CODING OR DECODING
- H03G: CONTROL OF AMPLIFICATION

## Abstract

A dynamic range control unit (210) configured to apply dynamic range control, referred to as DRC, to an audio signal (211). The DRC unit (210) is configured to downsample a subband signal (212) derived from the audio signal (211), to provide a downsampled subband signal (321), to determine a DRC gain (329) based on the downsampled subband signal (321), and to apply the DRC gain (329) to the subband signal (212), to provide a compressed subband signal (213) of a compressed audio signal (214).

## Claims

### Claim 1

A dynamic range control, referred to as DRC, unit configured to apply DRC to an audio signal; wherein the DRC unit is configured to
downsample a subband signal derived from the audio signal, to provide a downsampled subband signal;
determine a DRC gain based on the downsampled subband signal; and
apply the DRC gain to the subband signal, to provide a compressed subband signal of a compressed audio signal.

### Claim 2 (depends on 1)

The DRC unit of claim 1, wherein
a frame of the subband signal comprises N time slots and a corresponding frame of the downsampled subband signal comprises N/M time slots; and
M>1 is a downsampling factor.

### Claim 3 (depends on 2)

The DRC unit of claim 2, wherein the DRC unit is configured to
determine N/M DRC gains for the corresponding N/M time slots of the downsampled subband signal, based on the downsampled subband signal; and
upsample the N/M DRC gains to N DRC gains for the corresponding N time slots of the subband signal.

### Claim 4 (depends on 3)

The DRC unit of claim 3, wherein the DRC unit is configured to multiply N samples for the corresponding N time slots of the subband signal with the corresponding N DRC gains to determine the compressed subband signal, and/or wherein upsampling comprises
repeatedly using the same DRC gain for M subsequent time slots; or
interpolating between two successive DRC gains from the N/M DRC gains to determine M−1 DRC gains for M−1 subsequent time slots between the two successive DRC gains from the N/M DRC gains.

### Claim 5 (depends on 1)

The DRC unit of claim 1, wherein the DRC unit is configured to
downsample the subband signal without making use of a lowpass filter; and/or
downsampled subband signal by selecting every Mth sample of the subband signal as a sample of the downsampled subband signal.

### Claim 6 (depends on 1)

The DRC unit of claim 1, wherein
the audio signal is represented using K subband signals for K different frequency bins, with K>1; and
the DRC unit is configured to
group at least some of the K different frequency bins into Q DRC bands, with Q<K; and
determine a DRC gain for at least one of the Q DRC bands, based on the subband signals assigned to the at least one of the Q DRC bands, respectively.

### Claim 7 (depends on 6)

The DRC unit of claim 6, wherein the DRC unit is configured to ignore one or more of the K frequency bins when determining the DRC gain for the Q DRC bands.

### Claim 8 (depends on 1)

The DRC unit of claim 1, wherein the DRC unit is configured to
determine a loudness estimate for a sample of the downsampled subband signal; and
determine the gain value based on the loudness estimate using a compression curve.

### Claim 9 (depends on 8)

The DRC unit of claim 8, wherein the compression curve is defined by one or more parameters comprised within profile data, and/or wherein the DRC unit is configured to
determine a magnitude of the sample of the downsampled subband signal; and
apply Steven's power law and a conversion from a linear-domain to a logarithmic-domain to the magnitude of the sample of the downsampled subband signal to determine the loudness estimate for the sample of the downsampled subband signal.

### Claim 10 (depends on 8)

The DRC unit of claim 8, wherein
the compression curve is configured to provide a mapped gain value in dependence of a deviation of the loudness estimate from an operating point; and
the operating point is dependent on a dialnorm parameter or on an average dialog level of dialog content within the audio signal or on an average power level of the audio signal.

### Claim 11 (depends on 10)

The DRC unit of claim 10, wherein the DRC unit is configured to
determine an average block power value based on power values of a block of samples of the downsampled subband signal; and
determine the operating point for the block of samples of the downsampled subband signal also based on the average block power value.

### Claim 12 (depends on 11)

The DRC unit of claim 11, wherein the DRC unit is configured to
determine a long-term average block power value for the block of samples of the downsampled subband signal based on the average block power value for the block of samples of the downsampled subband signal and a sequence of previous blocks of samples of the downsampled subband signal;
determine a power deviation of the long-term average block power value from the dialnorm parameter; and
determine the operating point for a sample from the block of samples of the downsampled subband signal based on the power deviation.

### Claim 13 (depends on 1)

The DRC unit of claim 1, wherein the DRC unit is configured to
determine a mapped gain value for a sample of the downsampled subband signal for a current time slot based on a loudness estimate of the loudness of the sample of the downsampled subband signal for the current time slot;
perform gain smoothing of the mapped gain values for samples of the downsampled subband signal for the current time slot and for one or more previous time slots, to determine a smoothed gain value 326; for the sample of the downsampled subband signal for the current time slot; and
determine the DRC gain for the sample of the downsampled subband signal for the current time slot based on the smoothed gain value for the sample of the downsampled subband signal for the current time slot.

### Claim 14 (depends on 1)

The DRC unit of claim 1, wherein the DRC unit is configured to
determine a DRC gain for a sample of the downsampled subband signal; and
apply the DRC gain for the sample of the downsampled subband signal to a plurality of successive samples of the subband signal to determine the compressed subband signal.

### Claim 15 (depends on 1)

The DRC unit of claim 1, wherein
the audio signal comprises a plurality of different channels; and
the DRC unit is configured to determine a joint DRC gain for the plurality of different channels or for one or more subgroups of the plurality of different channels.

### Claim 16 (depends on 15)

The DRC unit of claim 15, wherein the DRC unit is configured to
select one of the channels from the plurality of different channels; and
determine a DRC gain for the selected channel as the joint DRC gain for the plurality of different channels or for the one or more subgroups of the plurality of different channels.

### Claim 17 (depends on 1)

The DRC unit of claim 1, wherein the DRC unit is configured to
determine and apply a plurality of DRC gains for a corresponding plurality of subband signals to provide a corresponding plurality of compressed subband signals; and
determine the compressed audio signal by applying an inverse transform or a synthesis filter bank to the plurality of compressed subband signals; wherein the inverse transform or synthesis filter bank are complementary to a forward transform or analysis filter bank used for deriving the subband signal from the audio signal.

### Claim 18 (depends on 1)

A decoding unit configured to derive a dynamic-range compressed audio signal from a bitstream indicative of an audio signal;
wherein the decoding unit comprises the DRC unit according to claim 1, configured to apply dynamic range control to the audio signal.

### Claim 19

A method for applying dynamic range control, referred to as DRC, to an audio signal; wherein the method comprises
downsampling a subband signal derived from the audio signal, to provide a downsampled subband signal;
determining a DRC gain based on the downsampled subband signal; and
applying the DRC gain to the subband signal, to provide a compressed subband signal of a compressed audio signal.

### Claim 20 (depends on 19)

A non-transitory computer-readable storage medium comprising instructions which, when executed by a processor cause the processor to perform the method of claim 19.