Post-processor, pre-processor, audio encoder, audio decoder and related methods for enhancing transient processing

Patent metadata

Field	Value
Publication number	US-10720170-B2
Application number	US-201815884190-A
Country	US
Kind code	B2
Filing date	Jan 30, 2018
Priority date	Feb 17, 2016
Publication date	Jul 21, 2020
Grant date	Jul 21, 2020

Abstract

An audio post-processor for post-processing an audio signal having a time-variable high frequency gain information as side information includes: a band extractor for extracting a high frequency band of the audio signal and a low frequency band of the audio signal; a high band processor for performing a time-variable modification of the high frequency band in accordance with the time-variable high frequency gain information to obtain a processed high frequency band; and a combiner for combining the processed high frequency band and the low frequency band. Furthermore, a pre-processor is illustrated.

First claim

The invention claimed is:

1. An audio post-processor for post-processing an audio signal comprising a time-variable high frequency gain information as side information, comprising:
a band extractor for extracting a high frequency band of the audio signal and a low frequency band of the audio signal;
a high band processor for performing a time-variable amplification of the high frequency band in accordance with the time-variable high frequency gain information to acquire a processed high frequency band; and
a combiner for combining the processed high frequency band and the low frequency band,
wherein the band extractor comprises: an analysis windower for generating a sequence of blocks of sampling values of the audio signal using an analysis window, wherein the blocks are time-overlapping; a discrete Fourier transform processor for generating a sequence of blocks of spectral values; a low pass shaper for shaping each block of spectral values to acquire a sequence of low pass shaped blocks of spectral values; a discrete Fourier inverse transform processor for generating a sequence of blocks of low pass time domain sampling values; and a synthesis windower for windowing the sequence of blocks of low pass time domain sampling values using a synthesis window, or
wherein the audio signal comprises an additional control parameter as a further side information, wherein the high band processor is configured to apply the time-variable amplification also under consideration of the additional control parameter, wherein a time resolution of the additional control parameter is lower than a time resolution of the time-variable high frequency gain information or the additional control parameter is stationary for a specific audio piece, or
wherein the band extractor, the high band processor and the combiner operate in overlapping blocks, wherein an overlap range is between 40% of a block length and 60% of a block length, or wherein a block length is between 0.8 milliseconds and 5 milliseconds, or wherein the time-variable amplification performed by the high band processor is a multiplicative factor applied to each sample of a block in a time domain, or wherein a cutoff or corner frequency of the low frequency band is between ⅛ and ⅓ of a maximum frequency of the audio signal or equal to ⅙ of the maximum frequency of the audio signal, or
wherein the band extractor, the high band processor and the combiner are configured to process sequences of blocks derived from the audio signal as overlapping blocks, so that a later portion of an earlier block is derived from the same audio samples of the audio signal as an earlier portion of a later block being adjacent in time to the earlier block, and wherein an overlap range of the overlapping blocks is equal to one half of the earlier block and wherein the later block comprises the same length as the earlier block with respect to a number of sample values, and wherein the post processor additionally comprises an overlap adder for performing the overlap add operation, or wherein the band extractor is configured to apply a slope of a splitting filter between a stop range and a pass range of the splitting filter to a block of audio samples, wherein the slope depends on the time-variable high frequency gain information for the block of samples, or wherein the high frequency gain information comprises gain values for adjacent blocks, wherein the high band processor is configured to calculate a correction factor for each sample depending on the gain values for the adjacent blocks and depending on window factors for corresponding samples, or wherein the audio post-processor further comprises an overlap-adder operating based on the following equation:

o
⁡

[

k
×

N
2

+
j

]

=

ob
⁡

[

k
-
1

]

⁡

[

j
+

N
2

]

+

ob
⁡

[
k
]

⁡

[
j
]

,

for
⁢

⁢
0

≤
j
<

N
2

o
⁡

[

(

k
+
1

)

×

N
2

+
j

]

=

ob
⁡

[
k
]

⁡

[

j
+

N
2

]

+

ob
⁡

[

k
+
1

]

⁡

[
j
]

,

Assignees

• Fraunhofer Ges Forschung

Inventors

• Ghido Florin
• Disch Sascha
• Herre Jürgen
• Adami Alexander
• Reutelhuber Franz

Classifications

• H03G3/00 Primary

  Gain control in amplifiers or frequency changers · CPC title

• H03G5/005 Primary

  of digital signals · CPC title

• G10L19/26

  Pre-filtering or post-filtering · CPC title

• G10L19/032 Primary

  Quantisation or dequantisation of spectral components · CPC title

• H03G5/165

  Equalizers; Volume or gain control in limited frequency bands · CPC title