Backward-compatible integration of high frequency reconstruction techniques for audio signals

Patent metadata

Field	Value
Publication number	US-12394424-B2
Application number	US-202418982382-A
Country	US
Kind code	B2
Filing date	Dec 16, 2024
Priority date	Jan 26, 2018
Publication date	Aug 19, 2025
Grant date	Aug 19, 2025

Abstract

A method for decoding an encoded audio bitstream is disclosed. The method includes receiving the encoded audio bitstream and decoding the audio data to generate a decoded lowband audio signal. The method further includes extracting high frequency reconstruction metadata and filtering the decoded lowband audio signal with an analysis filterbank to generate a filtered lowband audio signal. The method also includes extracting a flag indicating whether either spectral translation or harmonic transposition is to be performed on the audio data and regenerating a highband portion of the audio signal using the filtered lowband audio signal and the high frequency reconstruction metadata in accordance with the flag.

First claim

The invention claimed is:

1. A method for performing high frequency reconstruction of an audio signal, the method comprising:
receiving an encoded audio bitstream, the encoded audio bitstream including audio data representing a lowband portion of the audio signal and high frequency reconstruction metadata;
decoding the audio data to generate a decoded lowband audio signal;

extracting from the encoded audio bitstream the high frequency reconstruction metadata, the high frequency reconstruction metadata including operating parameters for a high frequency reconstruction process, the operating parameters including a patching mode parameter located in a backward-compatible extension container of the encoded audio bitstream, wherein a first value of the patching mode parameter indicates spectral translation and a second value of the patching mode parameter indicates harmonic transposition by phase-vocoder frequency spreading, wherein the encoded audio bitstream further includes a fill element with an identifier indicating a start of the fill element and fill data after the identifier, wherein the fill data includes the backward-compatible extension container, and wherein the identifier is a three bit unsigned integer transmitted most significant bit first and having a value of 0x6;
filtering the decoded lowband audio signal to generate a filtered lowband audio signal, wherein the filtering is performed by an analysis filterbank that includes analysis filters, h k (n), that are modulated versions of a prototype filter, p 0 (n), according to:

h
k

(
n
)

=

p
0

(
n
)

⁢
exp
⁢

{

i
⁢

π
M

⁢

(

k
+

1
2

)

⁢

(

n
-

N
2

)

}

,

0
≤
n
≤
N

;

0
≤
k
<
M

where p 0 (n) is a real-valued symmetric or asymmetric prototype filter, M is a number of channels in the analysis filterbank and N is an order of the prototype filter;
regenerating a highband portion of the audio signal using the filtered lowband audio signal and the high frequency reconstruction metadata, wherein the regenerating includes spectral translation if the patching mode parameter is the first value and the regenerating includes harmonic transposition by phase-vocoder frequency spreading if the patching mode parameter is the second value; and
combining the filtered lowband audio signal with the regenerated highband portion to form a wideband audio signal.

2. A non-transitory computer readable medium containing instructions that when executed by a processor perform the method of claim 1 .

3. An audio processing unit for performing high frequency reconstruction of an audio signal, the audio processing unit comprising:
an input interface for receiving an encoded audio bitstream, the encoded audio bitstream including audio data representing a lowband portion of the audio signal and high frequency reconstruction metadata;
a core audio decoder for decoding the audio data to generate a decoded lowband audio signal;
a deformatter for extracting from the encoded audio bitstream the high frequency reconstruction metadata, the high frequency reconstruction metadata including operating parameters for a high frequency reconstruction process, the operating parameters including a fill element with an identifier indicating a start of the fill element and fill data after the identifier, wherein the fill data includes a backward-compatible extension container including a patching mode parameter, wherein a first value of the patching mode parameter indicates spectral translation and a second value of the patching mode parameter indicates harmonic transposition by phase-vocoder frequency spreading, and wherein the identifier is a three bit unsigned integer transmitted most significant bit first and having a value of 0x6;
an analysis filterbank for filtering the decoded lowband audio signal to generate a filtered lowband audio signal, wherein the filtering is performed by an analysis filterbank that includes analysis filters, h k (n), that are modulated versions of a prototype filter, p 0 (n), according to:

h
k

(
n
)

=

p
0

(
n
)

⁢
exp
⁢

{

i
⁢

π
M

⁢

(

k
+

1
2

)

⁢

(

n
-

N
2

)

}

,

0
≤
n
≤
N

;

0
≤
k
<
M

Assignees

• Dolby Int Ab

Inventors

• Kjoerling Kristofer
• Villemoes Lars
• Purnhagen Heiko
• Ekstrand Per

Classifications

• H03M7/6011

  Encoder aspects · CPC title

• H03M7/6005

  Decoder aspects · CPC title

• G10L19/26

  Pre-filtering or post-filtering · CPC title

• G10L19/167 Primary

  Audio streaming, i.e. formatting and decoding of an encoded audio signal representation into a data stream for transmission or storage purposes · CPC title

• G10L19/02 Primary

  using spectral analysis, e.g. transform vocoders or subband vocoders · CPC title