Encoded audio metadata-based equalization

Patent metadata

Field	Value
Publication number	US-9934790-B2
Application number	US-201615060392-A
Country	US
Kind code	B2
Filing date	Mar 3, 2016
Priority date	Jul 31, 2015
Publication date	Apr 3, 2018
Grant date	Apr 3, 2018

Abstract

A system for producing an encoded digital audio recording has an audio encoder that encodes a digital audio recording having a number of audio channels or audio objects. An equalization (EQ) value generator produces a sequence of EQ values which define EQ filtering that is to be applied when decoding the encoded digital audio recording, wherein the EQ filtering is to be applied to a group of one or more of the audio channels or audio objects of the recording independent of any downmix. A bitstream multiplexer combines the encoded digital audio recording with the sequence of EQ values, the latter as metadata associated with the encoded digital audio recording. Other embodiments are also described including a system for decoding the encoded audio recording.

First claim

What is claimed is:

1. A system for producing a decoded digital audio recording, comprising:
a programmed processor that is to receive a bitstream in which a) an encoded digital audio recording having a plurality of original audio channels or audio objects is combined with b) a sequence of EQ values as metadata associated with the encoded audio recording, wherein the sequence of EQ values includes an indication of a specified EQ group of one or more channels or objects of the plurality of original audio channels or audio objects,
decode the plurality of original audio channels or audio objects, from the encoded digital audio recording,
group the decoded, plurality of original audio channels or audio objects into a plurality of EQ groups as specified in the metadata, and
filter the EQ groups independently of any downmix, in accordance with the sequence of EQ values in the metadata, wherein all of the channels or objects of a given EQ group are filtered using a filter cascade that is duplicated for each decoded channel or object in the given EQ group and is defined in accordance with the EQ values in the metadata.

2. The system of claim 1 wherein the metadata further specifies a dynamic range control, DRC, grouping for one or more of the plurality of original audio channels or audio objects, and an associated DRC sequence, and wherein the programmed processor is to group one or more of the filtered channels or objects of the plurality of EQ groups into a DRC group as specified in the metadata and perform DRC adjustment upon the channels or objects of the DRC group in accordance with the associated DRC sequence in the metadata.

3. The system of claim 1 wherein the programmed processor is to filter the plurality of EQ groups independent of any downmix, in response to a particular mode of operation, for playback of the decoded digital audio recording, being enabled either manually by a user or automatically based on a current time of day.

4. A method for producing a decoded digital audio recording, comprising:
receiving a bitstream in which a) an encoded digital audio recording having a plurality of original audio channels or audio objects has been combined with b) a sequence of EQ values including an indication of a specified EQ group, of one or more channels or objects of the plurality of original audio channels or audio objects, as metadata associated with the encoded digital audio recording;
decoding the plurality of original audio channels or audio objects, from the encoded digital audio recording;
grouping one or more of the decoded, original audio channels or audio objects to form an EQ group of channels or objects as specified in the metadata, and filtering all of the channels or objects of the EQ group independently of any downmix, using a filter cascade that is duplicated for each decoded channel or object in the EQ group and is defined in accordance with the EQ values in the metadata.

5. The method of claim 4 wherein the received metadata further specifies a dynamic range control, DRC, grouping for one or more of said original audio channels or audio objects, and an associated DRC sequence, the method further comprising
grouping one or more of the filtered channels or objects of the EQ group into a DRC group as specified in the metadata and performing DRC adjustment upon one or more channels or objects of the DRC group, in accordance with the associated DRC sequence in the metadata.

6. The method of claim 5 wherein the received metadata further specifies a downmix grouping for one or more of said original audio channels or audio objects, the method further comprising
grouping one or more of the DRC adjusted channels or objects into a downmix group and performing a downmix upon the downmix group, in accordance with the downmix grouping specified in the metadata.

7. A system for producing a decoded digital audio recording, comprising:
a programmed processor that is to receive a bitstream in which a) an encoded digital audio recording having a plurality of original audio channels or audio objects is combined with b) metadata associated with the encoded digital audio recording that includes a sequence of EQ values having an indication of a specified EQ group of one or more of the plurality of original audio channels or audio objects,
decode the plurality of original audio channels or audio objects, from the encoded audio recording,
group one or more of the decoded, original audio channels or audio objects into a decoded EQ group as specified in the metadata, and
filter the decoded EQ group independently of any downmix, wherein all of the channels or objects of the decoded EQ group are filtered using a filter cascade that is duplicated for each decoded channel or object in the decoded EQ group and is defined in accordance with the EQ values in the metadata.

8. The system of claim 7 wherein the programmed processor is to filter the decoded EQ group independent of any downmix that is as defined in the metadata, by reducing gain below 500 Hz, whether or not downmix is applied to the decoded EQ group.

9. The system of claim 7 wherein the programmed processor is to filter the decoded EQ group independent of any downmix, in response to a particular mode of operation, for playback of the decoded digital audio recording, being enabled either manually by a user or automatically based on a current time of day.

10. The system of claim 7 wherein the metadata specifies a downmix, pre-downmix EQ values for applying EQ prior to a downmix operation, and post-downmix EQ values.

11. The system of claim 7 wherein the programmed processor's filtering of the decoded EQ group is time varying or changes during playback of the decoded EQ group.

12. The system of claim 7 wherein the metadata further specifies grouping of the plurality of original audio channels or audio objects into one or more DRC groups, and wherein the metadata further includes a DRC sequence that is to be applied to all of the channels or objects in a given DRC group, and wherein the metadata specifies that said grouping for DRC is independent of a grouping for EQ.

13. The method of claim 4 wherein filtering the channels or objects of the EQ group independently of any downmix, in accordance with the EQ values in the metadata, comprises reducing gain below 500 Hz, whether or not downmix is applied to the EQ group.

14. The method of claim 4 wherein the sequence of EQ values defines said filtering as a late night mode that can be enabled during playback, of the decoded original audio channels or audio objects, either automatically by a decoder or manually by a user.

15. The method of claim 6 wherein the metadata specifies a downmix, pre-downmix EQ values for applying EQ prior to a downmix operation, and post-downmix EQ values.

16. The method of claim 6 wherein the metadata specifies loudness information for an EQ filtered version of the EQ group of one or more of the plurality of original audio channels or audio objects.

17. The method of claim 6 wherein filtering the channels or objects of the EQ group, in accordance with the EQ values in the metadata, is time varying or changes during playback of the decoded original audio channels or audio objects.

18. The system of claim 1 wherein the metadata further specifies grouping of the original plurality of audio channels or audio objects into one or more dynamic range control, DRC, groups, and wherein the metadata further includes a DRC sequence that is to be applied to all of the channels or objects in a given DRC group, and wherein the metadata spec

Assignees

• Apple Inc

Inventors

• Baumgarte Frank

Classifications

• H04S2400/15

  Aspects of sound capture and related signal processing for recording or reproduction · CPC title

• H04S2400/13

  Aspects of volume control, not necessarily automatic, in stereophonic sound systems · CPC title

• H04S2400/03

  Aspects of down-mixing multi-channel audio to configurations with lower numbers of playback channels, e.g. 7.1 -> 5.1 (H04S2400/01 takes precedence) · CPC title

• H04S7/307

  Frequency adjustment, e.g. tone control (H04S7/301 takes precedence) · CPC title

• H04S3/008

  in which the audio signals are in digital form, i.e. employing more than two discrete digital channels (data reduction aspects thereof based on psychoacoustics G10L19/02) · CPC title