U.S. patent application number 13/978175 was filed with the patent office on 2013-10-17 for signal processing device, method, and program.
This patent application is currently assigned to Sony Corporation. The applicant listed for this patent is Toru Chinen, Mitsuyuki Hatanaka. Invention is credited to Toru Chinen, Mitsuyuki Hatanaka.
Application Number | 20130275142 13/978175 |
Document ID | / |
Family ID | 46507130 |
Filed Date | 2013-10-17 |
United States Patent
Application |
20130275142 |
Kind Code |
A1 |
Hatanaka; Mitsuyuki ; et
al. |
October 17, 2013 |
SIGNAL PROCESSING DEVICE, METHOD, AND PROGRAM
Abstract
The present technology relates to a signal processing device,
method, and program that may obtain audio at a higher audio quality
when decoding an audio signal. An envelope information generating
unit 24 generates envelope information representing an envelope
form of high frequency components of an audio signal to be encoded.
A sine wave information generating unit 26 extracts a sine wave
signal from the high frequency components of the audio signal, and
generates a sine wave information representing an emergence start
position of the sine wave signal. An encoding stream generating
unit 27 multiplexes the envelope information, the sine wave
information, and low frequency components of the audio signal that
have been encoded, and outputs an encoding stream obtained as the
result. As a result, the high frequency components included in the
sine wave signal may be predicted at a higher accuracy from the
envelope information and the sine wave information at the receiving
side of the encoding stream. The present invention may be applied
to a signal processing device.
Inventors: |
Hatanaka; Mitsuyuki;
(Kanagawa, JP) ; Chinen; Toru; (Kanagawa,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Hatanaka; Mitsuyuki
Chinen; Toru |
Kanagawa
Kanagawa |
|
JP
JP |
|
|
Assignee: |
Sony Corporation
Tokyo
JP
|
Family ID: |
46507130 |
Appl. No.: |
13/978175 |
Filed: |
January 6, 2012 |
PCT Filed: |
January 6, 2012 |
PCT NO: |
PCT/JP2012/050173 |
371 Date: |
July 3, 2013 |
Current U.S.
Class: |
704/500 |
Current CPC
Class: |
G10L 19/0204 20130101;
G10L 19/0208 20130101; H03M 7/40 20130101; G10L 19/028 20130101;
G10L 19/093 20130101; G10L 21/038 20130101; G10L 19/008
20130101 |
Class at
Publication: |
704/500 |
International
Class: |
G10L 19/008 20060101
G10L019/008 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 14, 2011 |
JP |
2011-006233 |
Claims
1. A signal processing device comprising: an extracting unit
configured to extract an envelope information representing low
frequency components of an audio signal and an envelope of high
frequency components of the audio signal and a sine wave
information used for identifying the frequency and emergence
position of sine wave components included in the high frequency
components; a pseudo high frequency generating unit configured to
generate a pseudo high frequency signal configuring the high
frequency components on the basis of the low frequency signal as
the low frequency component and the envelope information; a sine
wave generating unit configured to generate a sine wave signal at a
frequency represented by the sine wave information and which
designates the emergence position identified from the sine wave
information as the start position; and a combining unit configured
to combine the low frequency signal, the pseudo high frequency
signal, and the sine wave signal to generate the audio signal.
2. The signal processing device according to claim 1, wherein the
sine wave information includes information representing the
distance from the start position of a frame of the high frequency
component until the emergence start position of the sine wave
component as information used for identifying the emergence
position.
3. The signal processing device according to claim 1, further
comprising: a noise generating unit configured to generate a noise
signal configuring the high frequency components by adjusting the
gain of each zone of a predetermined signal, in which the zones are
divided by a noise boundary position represented by a noise
envelope information, on the basis of information representing the
gain of each zone represented by the noise envelope information;
wherein the extracting unit further extracts the noise envelope
information; and wherein the sine wave information includes
information representing the distance from the noise boundary
position until the emergence start position of the sine wave
components as the information used for identifying the emergence
position; and wherein the combining unit combines the low frequency
signal, the pseudo high frequency signal, the sine wave signal, and
the noise signal to generate the audio signal.
4. The signal processing device according to claim 1, wherein the
sine wave information includes information representing the
distance from a peak position of the high frequency component
envelope until the emergence start position of the sine wave
component as the information used for identifying the emergence
position.
5. The signal processing device according to claim 1, wherein the
sine wave information is extracted for each frame, and the sine
wave generating unit generates the sine wave signal for the high
frequency components of each frame.
6. The signal processing device according to claim 1, wherein the
sine wave information is extracted for each band configuring the
high frequency components, and the sine wave generating unit
generates the sine wave signal for each band.
7. A signal processing method to control a signal processing
device, the signal processing device including an extracting unit
configured to extract an envelope information representing low
frequency components of an audio signal and an envelope of high
frequency components of the audio signal and a sine wave
information used for identifying the frequency and emergence
position of sine wave components included in the high frequency
components, a pseudo high frequency generating unit configured to
generate a pseudo high frequency signal configuring the high
frequency components on the basis of the low frequency signal as
the low frequency component and the envelope information, a sine
wave generating unit configured to generate a sine wave signal at a
frequency represented by the sine wave information and which
designates the emergence position identified from the sine wave
information as the start position, and a combining unit configured
to combine the low frequency signal, the pseudo high frequency
signal, and the sine wave signal to generate the audio signal, the
method comprising the steps of: the extracting unit extracting the
low frequency components, the envelope information, and the sine
wave information; the pseudo high frequency generating unit
generating the pseudo high frequency signal; the sine wave
generating unit generating the sine wave information; and the
combining unit combining the low frequency signal, the pseudo high
frequency signal, and the sine wave signal to generate the audio
signal.
8. A program executing processing on a computer, the processing
including the steps of envelope information representing low
frequency components of an audio signal and an envelope of high
frequency components of the audio signal and sine wave information
used for identifying the frequency and emergence position of sine
wave components included in the high frequency components are
extracted, a pseudo high frequency signal configuring the high
frequency components is generated on the basis of the low frequency
signal as the low frequency component and the envelope information,
a sine wave signal at a frequency represented by the sine wave
information and which designates the emergence position identified
from the sine wave information as the start position is generated,
and the low frequency signal, the pseudo high frequency signal, and
the sine wave information are combined to generate the audio
signal.
9. A signal processing device comprising: an envelope information
generating unit configured to generate envelope information
representing an envelope of a high frequency signal, which is the
high frequency component of an audio signal; a sine wave
information generating unit configured to detect a sine wave signal
included in the high frequency signal, and generating a sine wave
information used for identifying the frequency and emergence
position of the sine wave signal; and an output unit configured to
generate and outputting data made up from a low frequency signal,
which is a low frequency component of the audio signal, the
envelope information, and the sine wave information.
10. The signal processing device according to claim 9, wherein the
sine wave information includes information representing the
distance from the start position of a frame of the high frequency
component until the emergence start position of the sine wave
signal as information used for identifying the emergence
position.
11. The signal processing device according to claim 9, further
comprising: a noise envelope information generating unit configured
to detect a noise signal included in the high frequency signal, and
generating a noise envelope information made up from information
representing a noise boundary position which divides the noise
signal into a plurality of zones and information representing the
gain of the noise signal in the zone; wherein the sine wave
information includes information representing the distance from the
noise boundary position until the emergence start position of the
sine wave components as the information used for identifying the
emergence position; and wherein the output unit generates and
outputs data made up from the low frequency signal, the envelope
information, the sine wave information, and the noise envelope
information.
12. The signal processing device according to claim 9, wherein the
sine wave information includes information representing the
distance from a peak position of the high frequency component
envelope until the emergence start position of the sine wave
component as the information used for identifying the emergence
position.
13. The signal processing device according to claim 9, wherein the
sine wave information is generated for each frame.
14. The signal processing device according to claim 9, wherein the
sine wave information is generated for each band configuring the
high frequency components.
15. A signal processing method to control a signal processing
device, the signal processing device including an envelope
information generating unit configured to generate envelope
information representing an envelope of a high frequency signal,
which is the high frequency component of an audio signal; a sine
wave information generating unit configured to detect sine wave
information included in the high frequency signal, and generating a
sine wave information used for identifying the frequency and
emergence position of the sine wave signal; and an output unit
configured to generate and output data made up from the low
frequency signal, which is the low frequency component of the audio
signal, the envelope information, and the sine wave information,
the method comprising the steps of: the envelope information
generating unit generating the envelope information; the sine wave
information generating unit generating the sine wave information;
and the output unit generating and outputting data made up from the
low frequency signal, the envelope information, and the sine wave
information.
16. A program executing processing on a computer, the processing
including the steps of generating envelope information representing
an envelope of a high frequency signal, which is a high frequency
component of an audio signal, detecting a sine wave signal included
in the high frequency signal, and generating a sine wave
information used for identifying the frequency and emergence
position of the sine wave signal, and generating and outputting
data made up from a low frequency signal, which is a low frequency
component of the audio signal, the envelope information, and the
sine wave information.
Description
TECHNICAL FIELD
[0001] The present invention relates to a signal processing device,
method, and program, and particularly, relates to a signal
processing device, program, and method that enables audio to be
obtained at a higher audio quality in a case of decoding encoding
audio signals.
BACKGROUND ART
[0002] In general, audio signal encoding methods such as HE-AAC
(High Efficiency MPEG (Moving Picture Experts Group) 4 AAC
(Advanced Audio Coding)) (international standard ISO/IEC 14496-3)
are known. With such an encoding method, a high frequency feature
encoding technology such as SBR (Spectral Band Replication) is used
(for example, refer to PTL 1).
[0003] According to SBR, when encoding audio signals, SBR
information is output for generating high frequency components of
the audio signal (hereafter, referred to as high frequency signal)
together with low frequency components of the encoded audio signal
(hereafter, low frequency signal). At the decoding device, while
decoding the encoded low frequency signal, the high frequency
signal is generated by using the low frequency signal obtained by
the decoding and the SBR information, and so the audio signal made
up of the low frequency signal and the high frequency signal is
obtained.
[0004] This kind of SBR information includes envelope information
mainly representing an envelope form for the high frequency
components, and noise envelope information representing for
obtaining a noise signal added during the generation of the high
frequency components at the decoding device.
[0005] Here, the noise envelope information includes information
representing a boundary position for dividing each SBR frame of the
noise signal included in the high frequency components into two
zones (hereafter, referred to as the noise boundary position), and
information representing gain of noise signals in each zone.
Therefore, at the decoding device, a gain adjustment is performed
on each zone divided by the noise boundary position on a
predetermined noise signal on the basis of the noise envelope
information to establish a final noise signal. Further, with SBR,
it is also possible to set the gain on the entire SBR frame without
dividing the SBR frame of the noise signal into two zones.
[0006] When decoding the audio signal, the decoding device
generates the high frequency components by combining a pseudo high
frequency signal obtained from the low frequency signal and the
envelope information, and the noise signal obtained from the noise
envelope information, and generates the audio signal from the
obtained high frequency components and the low frequency
signal.
[0007] Also, with SBR, an encoding using sine wave synthesis is
performed on an audio signal with a high tone characteristic. That
is to say, when generating the high frequency components at the
decoding side, a sine wave signal of a particular frequency is
added to the pseudo high frequency signal in addition to the noise
signal. In this case, the signal obtained from combining the pseudo
high frequency signal, the noise signal, and the sine wave signal
is set to the high frequency signal obtained as a prediction.
[0008] When using a sine wave signal to predict the high frequency
components, a sine wave information representing the
existence/non-existence of the sine wave signal in the SBR frame is
included in the SBR information. Specifically, the combination
start position of the sine wave signal used during decoding is
either the start position of the SBR frame or the noise boundary
position, and the sine wave information is made up of binary
information representing the existence/non-existence of a sine wave
signal combination in each zone of the SBR frame divided by the
noise boundary position.
[0009] In this way, the noise signal and the sine wave signal added
to the pseudo high frequency signal are components that are
difficult to reproduce from the envelope information within the
high frequency components of the source audio signal. Therefore, by
combining the noise signal and the sine wave signal at a suitable
position in the pseudo high frequency signal, it is possible to
predict the high frequency components with higher accuracy, and it
is possible to reproduce audio at a higher audio quality by
performing band pass expansion using the high frequency components
obtained by prediction.
CITATION LIST
Patent Literature
[0010] PTL 1: Japanese Unexamined Patent Application Publication
(Translation of PCT Application) No. 2001-521648
SUMMARY OF INVENTION
Technical Problem
[0011] However, when using a sine wave signal to predict the high
frequency components, the combination start position of the sine
wave signal is set as the SBR frame start position or the noise
boundary position, which may cause variance in the emergence start
position of the sine wave components in the original audio signal,
in some cases. Thus, it is not possible to reproduce the high
frequency components with high accuracy, and may cause degradation
in the audible perception of the audio signal obtained from the
decoding.
[0012] Particularly with SBR, the frame length is fixed and not
dependent on the sampling rate of the audio signal to be encoded,
and so when the sampling rate is low, the absolute time length for
one frame becomes longer. For this reason, the amount of variance
(difference) in absolute time between the emergence start position
of the sine wave components in the source audio signal and the
combination start position of the sine wave signal to be combined
during decoding increases, and quantization noise becomes
noticeable at these zones of variance.
[0013] The present technology has been made taking this kind of
situation into consideration to enable the obtainment of audio at a
higher audio quality when decoding audio signals.
Solution to Problem
[0014] A signal processing device of a first aspect of the present
invention is provisioned with an extracting unit configured to
extract an envelope information representing low frequency
components of an audio signal and an envelope of high frequency
components of the audio signal and a sine wave information used for
identifying the frequency and emergence position of sine wave
components included in the high frequency components, a pseudo high
frequency generating unit configured to generate a pseudo high
frequency signal configuring the high frequency components on the
basis of the low frequency signal as the low frequency component
and the envelope information, a sine wave generating unit
configured to generate a sine wave signal at a frequency
represented by the sine wave information and which designates the
emergence position identified from the sine wave information as the
start position, and a combining unit configured to combine the low
frequency signal, the pseudo high frequency signal, and the sine
wave signal to generate the audio signal.
[0015] The sine wave information may include information
representing the distance from the start position of a frame of the
high frequency component until the emergence start position of the
sine wave component as information used for identifying the
emergence position.
[0016] The signal processing device is further provisioned with a
noise generating unit configured to generate a noise signal
configuring the high frequency components by adjusting the gain of
each zone of a predetermined signal, in which the zones are divided
by a noise boundary position represented by a noise envelope
information, on the basis of information representing the gain of
each zone represented by the noise envelope information, wherein
the extracting unit further extracts the noise envelope
information, the sine wave information includes information
representing the distance from the noise boundary position until
the emergence start position of the sine wave components as the
information used for identifying the emergence position, and the
combining unit may combines the low frequency signal, the pseudo
high frequency signal, the sine wave signal, and the noise signal
to generate the audio signal.
[0017] The sine wave information may include information
representing the distance from a peak position of the high
frequency component envelope until the emergence start position of
the sine wave component as the information used for identifying the
emergence position.
[0018] The sine wave information may be extracted for each frame,
and the sine wave generating unit may generate the sine wave signal
for the high frequency components of each frame.
[0019] The sine wave information may be extracted for each band
configuring the high frequency components, and the sine wave
generating unit may generate the sine wave signal for each
band.
[0020] A signal processing method or program of the first aspect of
the present invention includes the steps of extracting the low
frequency components of the audio signal, the envelope information
representing the envelope of the high frequency component of the
audio signal, and the sine wave information used for identifying
the frequency and emergence start position of the sine wave
component included in the high frequency components, generating the
pseudo high frequency signal configuring the high frequency
components on the basis of a low frequency signal as the low
frequency component and the envelope information, generating a sine
wave signal at the frequency represented by the sine wave
information at a start position identified by the emergence start
position from the sine wave information, and combining the low
frequency signal, the pseudo high frequency signal, and the sine
wave signal to generate the audio signal.
[0021] Regarding the first aspect of the present invention, the
envelope information representing low frequency components of an
audio signal and an envelope of high frequency components of the
audio signal and sine wave information used for identifying the
frequency and emergence position of sine wave components included
in the high frequency components are extracted, a pseudo high
frequency signal configuring the high frequency components is
generated on the basis of the low frequency signal as the low
frequency component and the envelope information, a sine wave
signal at a frequency represented by the sine wave information and
which designates the emergence position identified from the sine
wave information as the start position is generated, and the low
frequency signal, the pseudo high frequency signal, and the sine
wave signal are combined to generate the audio signal.
[0022] A signal processing device of a second aspect of the present
invention is provisioned with an envelope information generating
unit configured to generate envelope information representing an
envelope of a high frequency signal, which is the high frequency
component of an audio signal, a sine wave information generating
unit configured to detect a sine wave signal included in the high
frequency signal, and generating a sine wave information used for
identifying the frequency and emergence position of the sine wave
signal, and an output unit configured to generate and output data
made up from a low frequency signal, which is a low frequency
component of the audio signal, the envelope information, and the
sine wave information.
[0023] The sine wave information may include information
representing the distance from the start position of a frame of the
high frequency component until the emergence start position of the
sine wave signal as information used for identifying the emergence
position.
[0024] The signal processing device is further provisioned with a
noise envelope information generating unit configured to detect a
noise signal included in the high frequency signal, and generating
a noise envelope information made up from information representing
a noise boundary position which divides the noise signal into
multiple zones and information representing the gain of the noise
signal in the zone, wherein the sine wave information includes
information representing the distance from the noise boundary
position until the emergence start position of the sine wave
components as the information used for identifying the emergence
position, and the output unit may generate and output data made up
from the low frequency signal, the envelope information, the sine
wave information, and the noise envelope information.
[0025] The sine wave information may include information
representing the distance from a peak position of the high
frequency component envelope until the emergence start position of
the sine wave component as the information used for identifying the
emergence position.
[0026] The sine wave information may be generated for each
frame.
[0027] The sine wave information may be generated for each band
configuring the high frequency components.
[0028] A signal processing method or program of the second aspect
of the present invention includes the steps of generating envelope
information representing an envelope of a high frequency signal,
which is the high frequency component of an audio signal,
generating sine wave information included in the high frequency
signal is detected, and a sine wave information used for
identifying the frequency and emergence position of the sine wave
signal, and generating and outputting data made up from a low
frequency signal, which is the low frequency component of the audio
signal, the envelope information, and the sine wave
information.
[0029] Regarding the second aspect of the present invention,
envelope information representing an envelope of a high frequency
signal, which is a high frequency component of an audio signal, is
generated, a sine wave signal included in the high frequency signal
is detected, and a sine wave information used for identifying the
frequency and emergence position of the sine wave signal is
generated, and data made up from a low frequency signal, which is a
low frequency component of the audio signal, the envelope
information, and the sine wave information is generated and
output.
Advantageous Effects of Invention
[0030] According to the first aspect and the second aspect of the
present technology, audio may be obtained at a higher audio quality
when decoding an audio signal.
BRIEF DESCRIPTION OF DRAWINGS
[0031] FIG. 1 is a diagram illustrating a configuration example of
a first Embodiment of an encoding device.
[0032] FIG. 2 is a flowchart describing an encoding processing.
[0033] FIG. 3 is a diagram illustrating a combination start
position of a sine wave signal.
[0034] FIG. 4 is a diagram illustrating a combination start
position of a sine wave signal.
[0035] FIG. 5 is a diagram illustrating a configuration example of
the first Embodiment of a decoding device.
[0036] FIG. 6 is a flowchart describing a decoding processing.
[0037] FIG. 7 is a flowchart describing a processing to generate
the sine wave signal.
[0038] FIG. 8 is a diagram illustrating a configuration example of
another encoding device.
[0039] FIG. 9 is a flowchart describing an encoding processing.
[0040] FIG. 10 is a diagram describing a combination start position
of the sine wave signal.
[0041] FIG. 11 is a diagram illustrating a configuration example of
another decoding device.
[0042] FIG. 12 is a flowchart describing a decoding processing.
[0043] FIG. 13 is a flowchart describing a processing to generate
the sine wave signal.
[0044] FIG. 14 is a diagram illustrating a configuration example of
another encoding device.
[0045] FIG. 15 is a flowchart describing an encoding
processing.
[0046] FIG. 16 is a diagram describing a combination start position
of the sine wave signal.
[0047] FIG. 17 is a diagram illustrating a configuration example of
another decoding device.
[0048] FIG. 18 is a flowchart describing a decoding processing.
[0049] FIG. 19 is a flowchart describing a processing to generate
the sine wave signal.
[0050] FIG. 20 is a diagram illustrating a configuration example of
another encoding device.
[0051] FIG. 21 is a flowchart describing an encoding
processing.
[0052] FIG. 22 is a diagram illustrating a configuration example of
another decoding device.
[0053] FIG. 23 is a flowchart describing a decoding processing.
[0054] FIG. 24 is a flowchart describing a processing to generate
the sine wave signal.
[0055] FIG. 25 is a diagram illustrating a configuration example of
a computer.
DESCRIPTION OF EMBODIMENTS
[0056] Hereafter, the embodiments applying the present technology
will be described with reference to the drawings.
First Embodiment
[Configuration Example of Encoding Device]
[0057] FIG. 1 is a diagram illustrating a configuration example of
a first Embodiment of an encoding device applying the present
technology.
[0058] An encoding device 11 is configured with a downsampler 21, a
low frequency encoding unit 22, a band pass division filter 23, an
envelope information generating unit 24, a noise envelope
information generating unit 25, a sine wave information generating
unit 26, and an encoding stream generating unit 27. The encoding
device 11 encodes and outputs an input audio signal, and the audio
signal input into the encoding device 11 is supplied to the
downsampler 21 and the band pass division filter 23.
[0059] The downsampler 21 extracts the low frequency signal, which
is the low frequency components of the audio signal, by
downsampling the input audio signal, and supplies this to the low
frequency encoding unit 22 and the noise envelope information
generating unit 25. Further, hereafter, the frequency band
components at or below a certain frequency of the audio signal are
referred to as the low frequency components, and the frequency band
components higher than the low frequency components of the audio
signal are referred to as the high frequency components.
[0060] The low frequency encoding unit 22 encodes the low frequency
signal supplied from the downsampler 21, and supplies this to the
encoding stream generating unit 27.
[0061] The band pass division filter 23 conducts a filter
processing on the input audio signal, and performs a band pass
division of the audio signal. As a result of this band pass
division, the audio signal is divided into a signal of multiple
band components. Further, hereafter, each band signal configuring
the high frequency components from within each band signal obtained
by the band pass division is referred to as the high frequency
signal. The band pass division filter 23 supplies the high
frequency signal from the high frequency side of each band obtained
by the band pass division to the envelope information generating
unit 24, the noise envelope information generating unit 25, and the
sine wave information generating unit 26.
[0062] The envelope information generating unit 24 generates an
envelope information representing a form of an envelope (envelope)
for the high frequency signal of the band for each band on the high
frequency side on the basis of the high frequency signal supplied
from the band pass division filter 23, and then supplies this to
the noise envelope information generating unit 25. Also, the
envelope information generating unit 24 is provisioned with an
encoding unit 41, and the encoding unit 41 encodes the envelope
information generated by the envelope information generating unit
24, and supplies this to the encoding stream generating unit
27.
[0063] The noise envelope information generating unit 25 generates
a noise envelope information while receiving information from the
sine wave information generating unit 26 as necessary, on the basis
of the high frequency signal from the band pass division filter 23
and the envelope information from the envelope information
generating unit 24.
[0064] Here, the noise envelope information is information made up
from information representing a boundary position (noise boundary
position) for dividing the noise signal included in the high
frequency components of the audio signal, and information
representing the noise signal gain for each zone divided at the
noise boundary position. Further, the noise signal is a previously
determined signal.
[0065] Also, the noise envelope information generating unit 25 is
provisioned with a signal generating unit 51, a boundary
calculating unit 52, and an encoding unit 53. When generating noise
envelope information, the signal generating unit 51 predicts the
high frequency side of the audio signal for each band component on
the basis of the low frequency signal from the downsampler 21 and
the envelope information from the envelope information generating
unit 24.
[0066] The boundary calculating unit 52 determines the noise
boundary position used for dividing the noise signal into multiple
zones on the basis of the noise signal envelope obtained from the
high frequency signal and a pseudo high frequency signal, which is
the result of the high frequency side of each band pass component
predicted during the generation of the noise envelope information.
The encoding unit 53 encodes the noise envelope information
generated by the noise envelope information generating unit 25, and
supplies this to the encoding stream generating unit 27.
[0067] The sine wave information generating unit 26 generates sine
wave information used for obtaining the sine wave signal included
in the band for each band at the high frequency side while
receiving the information from the noise envelope information
generating unit 25 as necessary, on the basis of the high frequency
signal supplied from the band pass division filter 23.
[0068] Here, the sine wave information is information made up from
information representing the existence/non-existence of a sine wave
signal included in the high frequency components of the audio
signal, and information used for identifying the emergence start
position of the sine wave signal. That is to say, the sine wave
information may be information made up from information
representing the existence/non-existence of a sine wave signal to
be combined with the pseudo high frequency components during
decoding of the audio signal, and information representing the
combination start position of the sine wave signal.
[0069] Also, then sine wave information generating unit 26 is
provisioned with a sine wave detection unit 61, a position
detection unit 62, and an encoding unit 63. The sine wave detection
unit 61 detects the existence/non-existence of the sine wave
components from the high frequency signal during generation of the
sine wave information.
[0070] When generating sine wave information, the position
detection unit 62 detects the combination start position indicating
where the combination of the sine wave signal should start, that is
to say, the emergence start position of the sine wave signal, on
the basis of the high frequency signal from the band pass division
filter 23. The encoding unit 63 encodes the sine wave information
generated by the sine wave information generating unit 26, and
supplies this to the encoding stream generating unit 27.
[0071] The encoding stream generating unit 27 encodes the low
frequency signal from the low frequency encoding unit 22, the
envelope information from the envelope information generating unit
24, the noise envelope information from the noise envelope
information generating unit 25, and the sine wave information from
the sine wave information generating unit 26, and outputs the
encoding stream obtained from this encoding. That is to say, the
low frequency signal, the envelope information, the noise envelope
information, and the sine wave information are multiplexed into the
encoding stream.
[Description of Encoding Processing]
[0072] Next, the operation of the encoding device 11 will be
described.
[0073] When the audio signal is input into the encoding device 11,
and instructed to encode the audio signal, the encoding device 11
performs the encoding processing to perform the encoding of the
audio signal, and outputs the encoding stream obtained as the
result. Hereafter, the encoding processing by the encoding device
11 will be described with reference to the flowchart in FIG. 2.
[0074] At a step S11, the downsampler 21 downsamples the input
audio signal to generate the low frequency signal, and supplies
this to the noise envelope information generating unit 25 and the
low frequency encoding unit 22.
[0075] At a step S12, the low frequency encoding unit 22 encodes
the low frequency signal supplied from the downsampler 21, and
supplies this to the encoding stream generating unit 27. For
example, the low frequency signal is encoded by an encoding method
such as MPEG4 AAC, MPEG2 AAC, CELP (Code Exited Linear Prediction),
TCX (Transform Coded Excitation), or AMR (Adaptive Multi-Rate).
[0076] At a step S13, the band pass division filter 23 divides the
input audio signal into bands, and the high frequency components
obtained as the result are supplied to the envelope information
generating unit 24 through the sine wave information generating
unit 26. For example, high frequency signals may be obtained as
high frequency components from 64 different bands.
[0077] At a step S14, the envelope information generating unit 24
generates the envelope information for each band on the basis of
the high frequency signal for each band supplied from the band pass
division filter 23. For example, the envelope information
generating unit 24 may designate a zone made up of 32 samples of
the high frequency signal as one frame, and generate the envelope
information for each band per frame.
[0078] Specifically, the envelope information generating unit 24
obtains an average sample value of two samples of the high
frequency signal neighboring on a time line in one frame, and this
average value becomes the new high frequency signal sample value.
As a result, the high frequency signal for one frame is converted
from a 32-sample signal to a 16-sample signal.
[0079] Next, the envelope information generating unit 24 performs a
difference encoding on the high frequency signal that is now 16
samples, and the information obtained as the result becomes the
envelope information. For example, the difference between the
sample value of two high frequency signal samples to be processed
neighboring on a time line is obtained by the difference encoding,
and this difference becomes the envelope information. Also, the
envelope information may be made up of the difference between the
sample value of a sample of the high frequency signal of the band
to be processed and the sample value of a sample in a band adjacent
to that band, in the same position as the high frequency signal
band, for example.
[0080] The envelope information obtained in this way is the
information representing the form of the envelope for one frame of
the high frequency signal. The encoding unit 41 performs a variable
length encoding such as Huffman encoding on the generated envelope
information, and supplies the encoded envelope information to the
encoding stream generating unit 27. Also, the envelope information
generating unit 24 supplies the envelope information to the noise
envelope information generating unit 25.
[0081] Further, hereafter, the high frequency signal will continue
to be described as that processed in units of one frame configured
of 32 samples. Also, hereafter, the zone configured from two
samples of the high frequency signal (audio signal) will be called
one timeslot.
[0082] At a step S15, the signal generating unit 51 in the noise
envelope information generating unit 25 generates the pseudo high
frequency signal for each band at the high frequency side on the
basis of the envelope information supplied from the envelope
information generating unit 24 and the low frequency signal
supplied from the downsampler 21.
[0083] For example, the signal generating unit 51 extracts the zone
for one frame of a predetermined band of the low frequency signal,
and manipulates the extracted low frequency signal into the
envelope form represented by the envelope information. That is to
say, the sample value of the sample of the low frequency signal is
increased or decreased so that the position gain corresponding to
the sample fits in the envelope represented by the envelope
information, and the signal obtained as the result becomes the
pseudo high frequency signal.
[0084] The pseudo high frequency signal obtained in this way has
the almost the same envelope form as the envelope of the actual
high frequency signal represented by the envelope information. That
is to say, the pseudo high frequency signal is generated from the
low frequency signal and the envelope information.
[0085] At a step S16, the noise envelope information generating
unit 25 extracts the difference between the high frequency signal
and the pseudo high frequency signal for each band at the high
frequency side, and obtains the envelope for the noise signal
(hereafter, referred to as the noise envelope).
[0086] Further, more specifically, the noise envelope obtained at
step S16 is a virtual noise envelope. The receiving side of the
encoding stream output from the encoding device 11 predicts the
high frequency components of the audio signal during the decoding
of the audio signal, but this prediction is performed by combining
of the pseudo high frequency signal, the noise signal, and the sine
wave signal.
[0087] That is to say, the high frequency components of the actual
audio signal are assumed to include the pseudo high frequency
signal, the noise signal, and the sine wave signal. Here, at the
step S16, the difference between the high frequency signal and the
pseudo high frequency signal is obtained, and this difference
should be the combination of the noise signal and the sine wave
signal. Thus, the difference obtained in this way is considered as
the envelope of the noise signal including the sine wave
signal.
[0088] The noise envelope information generating unit 25 supplies
the virtual noise envelope for each band at the high frequency side
obtained as previously described to the sine wave information
generating unit 26.
[0089] At a step S17, the sine wave detection unit 61 in the sine
wave information generating unit 26 detects the sine wave
components from the high frequency signal for each band on the
basis of the virtual noise envelope supplied from the noise
envelope information generating unit 25.
[0090] For example, the sine wave detection unit 61 conducts a
frequency conversion on the virtual noise envelope, and converts
the noise envelope into frequency components. Then, when there are
frequency spikes having high power in the obtained frequency
components, the sine wave detection unit 61 recognizes these
frequency components as the sine wave components. Specifically,
when the difference between the power of the frequency under
observation and the power of other surrounding frequencies is at or
above a predetermined threshold, the frequency under observation is
recognized as the sine wave component. The sine wave signal for the
frequency detected in this way is determined as the sine wave
signal included in the actual high frequency components.
[0091] At a step S18, the position detection unit 62 in the sine
wave information generating unit 26 detects, for each band, the
combination start position where the sine wave signal, which is the
detected sine wave component, should be combined on the basis of
the high frequency signal supplied from the band pass division
filter 23.
[0092] For example, the position detection unit 62 obtains the
difference between the average sample value of the samples included
in one timeslot of the high frequency signal, in units of
timeslots, and the average sample value of samples included in one
timeslot of the detected sine wave signal. Then, the position
detection unit 62 determines the combination start position looking
from the beginning of the zone for one frame as the final position
(start position of the timeslot or the final position of the
sample) where the value of the obtained difference is at or above a
predetermined threshold. This combination start position is the
emergence start position of the sine wave signal included in the
actual high frequency signals, from a timing after the combination
start position, the difference in the average sample values of the
high frequency signal and the sine wave signal should decrease.
[0093] Also, for each band at the high frequency side, the sine
wave information generating unit 26 supplies the information
representing whether or not the sine wave has been detected from
the bands, the information representing the frequency and power of
the detected sine wave signal, and the combination start position
to the noise envelope information generating unit 25.
[0094] At a step S19, the sine wave information generating unit 26
generates the sine wave information for each band at the high
frequency side, and supplies this to the encoding stream generating
unit 27.
[0095] For example, the sine wave information generating unit 26
designates the information made up from the information
representing whether or not the sine wave signal has been detected
from the high frequency band and the combination start position as
the sine wave information. Also, during the generation of the sine
wave information, the encoding unit 63 in the sine wave information
generating unit 26 performs the variable length encoding of the
information representing the combination start position.
[0096] Here, the information representing whether or not the sine
wave signal has been detected is, more specifically, information
representing which frequency in the high frequency band is the sine
wave component. For example, when multiple sine wave signals are
detected from the high frequency band, the information used for
identifying the frequencies of these sine wave signals is
designated as the information representing whether or not the sine
wave signals were detected. Also, when multiple sine wave signals
are detected from the high frequency band, information representing
the combination start position is generated for each sine wave
signal.
[0097] Also, when the sine wave component is not detected from the
high frequency band, the sine wave information made up only of
information representing whether or not the sine wave signal has
been detected is transmitted to the decoding side. That is to say,
the sine wave information not including information representing
the combination start position is transmitted.
[0098] Further, the encoding device 11 may select whether or not to
transmit the sine wave information to the decoding side per frame.
In this way, by enabling the transmission of the sine wave
information to be selectable, transfer efficiency of the encoding
stream in increased, and at the same time, a resetting of the time
information of the sine wave components may be performed. As a
result, when starting the decoding processing from an arbitrary
frame within the stream on the decoding side of the encoding
stream, the sine wave component from the frame including the
information representing the combination start position may be
started.
[0099] Further, as illustrated in FIG. 3 for example, the
combination start position on the decoding side has conventionally
been either the start position of the frame or the noise boundary
position. Further, the horizontal axis in the figure represents the
time line. Also, an arrow FS1 and an arrow FE1 in FIG. 3 represent
the start position and end position of the frame, respectively.
[0100] According to the example in FIG. 3, the position represented
by an arrow N1 is the noise boundary position, and the combination
start position of the sine wave signal is also in the same position
as the noise boundary position. Therefore, the sine wave signal is
combined in a zone from the position represented by the arrow N1
until the end position of the frame.
[0101] However, when the position that sine wave signal included in
the actual high frequency components arrives is after the noise
boundary position represented by the arrow N1, for example, at the
decoding side, unnecessary sine wave components are added in the
space from the noise boundary position to the emergence start
position of the actual sine wave signal. In this case, there is an
unpleasant audible sensation in the audio signal obtained by the
decoding, and audio at a high audio quality is unable to be
obtained.
[0102] Regarding this, as illustrated in FIG. 4, according to the
encoding device 11, the combination start position output to the
decoding side is not limited to being the same as the noise
boundary position. Further, the horizontal axis in the figure
represents the time line. Also, an arrow FS2 and arrow FE2 in FIG.
4 represent the start position and the end position of the frame,
respectively.
[0103] According to the example in FIG. 4, the position represented
by an arrow N2 represents the noise boundary position. Also, the
combination start position of the sine wave signal is the position
represented by an arrow G1, and this combination start position is
before the noise boundary position. According to this example, the
sine wave signal is combined in the zone from the combination start
position represented by the arrow G1 until the end position of the
frame.
[0104] Also, in this case, the information representing the length
of time (time distance) from the start position of the frame
represented by the arrow FS2 until the combination start position
represented by the arrow G1 is designated as the information
representing the combination start position. Here, the time from
the beginning of the frame until the combination start position is
an integral multiple of the timeslot length.
[0105] In this way, by specifying the combination start position
independent of the noise boundary position, the combination of
unnecessary signals is prevented during the decoding of the audio
signal, and audio at a higher audio quality may be obtained.
[0106] Further, the sine wave information has been previously
described as information generated representing the combination
start position for the high frequency side for each band, but the
sine wave information may use a representative value of the
combination start positions for these bands shared for each band
configuring the high frequency. In such a case, for example, the
information representing the combination start position for the
band out of multiple bands configuring the high frequency which has
the sine wave signal of the highest power becomes the sine wave
information.
[0107] Also, the information representing the combination start
position has been described above as the sine wave information to
which variable length encoding has been performed, but the
information representing the combination start position may not be
encoded.
[0108] Returning to the description of the flowchart in FIG. 2, at
the step S19, the sine wave information is generated, and
afterwards, processing proceeds to a step S20.
[0109] At a step S20, the boundary calculating unit 52 in the noise
envelope information generating unit 25 detects the noise boundary
position for each band at the high frequency side.
[0110] For example, the boundary calculating unit 52 generates the
sine wave information included in the frame for the band
configuring the high frequency on the basis of the information
representing whether or not the sine wave signal has been detected,
the information representing the frequency and power of the sine
wave signal, and the combination start position. For example, when
the sine wave signal is detected, the zone from the beginning of
the frame until the combination start position is designated as a
silent zone, and the zone from this point is made up of the sine
wave component of a predetermined amplitude of the detected
frequency. At this time, the amplitude of the sine wave signal is
determined from the information representing the power of the sine
wave signal supplied from the sine wave information generating unit
26. Also, when the sine wave signal is not detected, the amplitude
of the sine wave signal is set to zero.
[0111] Next, the boundary calculating unit 52 subtracts the sine
wave signal obtained in this way from the virtual noise envelope
obtained at a step S16 to obtain the final noise envelope. Then,
the boundary calculating unit 52 determines the noise boundary
position according to the distribution of the final noise envelope
gain.
[0112] That is to say, the boundary calculating unit 52 divides the
frame into two zones as necessary based on the distribution of the
gain of the final noise envelope. Specifically, when the noise
envelope gain is nearly the same value for the entire frame of the
band being processed, the division of the frame is not performed.
That is to say, there is no noise boundary position.
[0113] Also, when there is a large difference in the gain
distribution of the noise envelope at a predetermined position in
the frame for the zone before this position and the zone after this
position, this position becomes the noise boundary position.
Further, the noise boundary position is designated as the timeslot
boundary position.
[0114] At a step S21, the noise envelope information generating
unit 25 generates the noise envelope information for each band at
the high frequency side, and supplies this to the encoding stream
generating unit 27.
[0115] For example, the noise envelope information generating unit
25 designates the noise envelope information as the information
made up from the noise boundary position, and the noise signal gain
in each zone in the frame divided by this noise boundary position.
At this time, the encoding unit 53 performs an encoding of the
information representing the noise boundary position, and a
variable length encoding of the information representing the gain
for each divided zone.
[0116] Here, the gain for each divided zone is the average gain
value of the noise envelope in these zones, for example. That is to
say, the frame being processed is divided into two zones by the
noise boundary position. In this case, the gain for the zone from
the beginning of the frame until the noise boundary position is the
average gain value for each position of the final noise envelope in
this zone.
[0117] At a step S22, the encoding stream generating unit 27
encodes the low frequency signal from the low frequency encoding
unit 22, the envelope information from the envelope information
generating unit 24, the noise envelope information from the noise
envelope information generating unit 25, and the sine wave
information from the sine wave information generating unit 26, and
generates the encoding stream. Then, the encoding stream generating
unit 27 transmits the encoding stream obtained from the encoding to
the decoding device, etc., and the encoding processing
terminates.
[0118] In this way, the encoding device 11 generates and outputs
the encoding stream made up from the low frequency signal, the
envelope information, the noise envelope information, and the sine
wave information. At this time, by a more accurate combination
start position of the sine wave signal being detected, and
generating the sine wave information including this combination
start position, a more accurate sine wave signal combination may be
performed at the decoding side of the audio signal, which results
in the obtainment of audio at a higher audio quality.
[0119] Further, the low frequency signal generated by the
downsampler 21 has been described above to be supplied to the noise
envelope information generating unit 25, but the low frequency
signal supplied to the noise envelope information generating unit
25 may be a low frequency signal obtained by division of the bands
by the band pass division filter 23. Also, the low frequency signal
encoded by the low frequency encoding unit 22 is obtained by
decoding, but this may also be supplied to the noise envelope
information generating unit 25.
[Configuration Example of Decoding Device]
[0120] Next, a decoding device which receives the encoding stream
output from the encoding device 11 in FIG. 1, and obtains the audio
signal from the encoding stream will be described. This kind of
decoding device is configured as illustrated in FIG. 5, for
example.
[0121] A decoding device 91 in FIG. 5 is configured with an
encoding stream decoding unit 101, a low frequency decoding unit
102, an envelope information decoding unit 103, a noise envelope
information decoding unit 104, a sine wave information decoding
unit 105, and a band pass combination filter 106.
[0122] The encoding stream decoding unit 101 receives and decodes
the encoding stream transmitted from the encoding device 11. That
is to say, the encoding stream decoding unit 101 inverse
multiplexes the encoding stream, and the low frequency signal, the
envelope information, the noise envelope information, and the sine
wave information obtained as a result is supplied to the low
frequency decoding unit 102, the envelope information decoding unit
103, the noise envelope information decoding unit 104, and the sine
wave information decoding unit 105, respectively.
[0123] The low frequency decoding unit 102 decodes the low
frequency signal supplied from the encoding stream decoding unit
101, and supplies this to the envelope information decoding unit
103 and the band pass combination filter 106.
[0124] The envelope information decoding unit 103 decodes the
envelope information supplied from the encoding stream decoding
unit 101, and also supplies the decoded envelope information to the
sine wave information decoding unit 105. Also, the envelope
information decoding unit 103 is provisioned with a generating unit
121, and the generating unit 121 generates envelop information and
the pseudo high frequency signal based on the low frequency signal
from the low frequency decoding unit 102, and supplies this to the
band pass combination filter 106.
[0125] The noise envelope information decoding unit 104 decodes the
noise envelope information supplied from the encoding stream
decoding unit 101. Also, the noise envelope information decoding
unit 104 is provisioned with a generating unit 131, and the
generating unit 131 generates the noise signal based on the noise
envelope information, and supplies this to the band pass
combination filter 106.
[0126] The sine wave information decoding unit 105 decodes the sine
wave information supplied from the encoding stream decoding unit
101. Also, the sine wave information decoding unit 105 is
provisioned with a generating unit 141, and the generating unit 141
generates the sine wave signal based on the sine wave information
and envelope information from the envelope information decoding
unit 103, and supplies this to the band pass combination filter
106.
[0127] The band pass combination filter 106 combines the bands of
the low frequency signal from the low frequency decoding unit 102,
the pseudo high frequency signal from the envelope information
decoding unit 103, the noise signal from the noise envelope
information decoding unit 104, and the sine wave signal from the
sine wave information decoding unit 105 to generate the audio
signal. The band pass combination filter 106 outputs the signal
obtained from combining the bands as the decoded audio signal to a
downstream player unit or similar.
[Description of Decoding Processing]
[0128] When the encoding stream from the encoding device 11 is
transmitted to the decoding device 91 illustrated in FIG. 5, the
decoding device 91 performs the decoding processing in units of
frames to decode the audio signal. Hereafter, the decoding
processing performed by the decoding device 91 will be described
with reference to FIG. 6.
[0129] At a step S1, the encoding stream decoding unit 101 decodes
the encoding stream received from the encoding device 11, and
supplies the low frequency signal, envelope information, noise
envelope information, and sine wave information obtained as a
result to the low frequency decoding unit 102 through the sine wave
information decoding unit 105.
[0130] At a step S52, the low frequency decoding unit 102 decoded
the low frequency signal from the encoding stream decoding unit
101, and supplies this to the envelope information decoding unit
103 and the band pass combination filter 106.
[0131] At a step S53, the envelope information decoding unit 103
decodes the envelope information from the encoding stream decoding
unit 101. Also, the envelope information decoding unit 103 supplies
the decoded envelope information to the sine wave information
decoding unit 105.
[0132] At a step S54, the generating unit 121 in the envelope
information decoding unit 103 generates the pseudo high frequency
signal for each band at the high frequency side, on the basis of
the low frequency signal from the low frequency decoding unit 102,
and supplies this to the band pass combination filter 106. For
example, the generating unit 121 generates the pseudo high
frequency signal by extracting the zone for one frame regarding a
predetermined band of the low frequency signal, and increasing or
decreasing the low frequency signal so that the sample value of the
extracted low frequency signal sample matches the gain of the
position in the envelope represented by the envelope information
corresponding to this sample.
[0133] At a step S55, the noise envelope information decoding unit
104 decodes the noise envelope information from the encoding stream
decoding unit 101.
[0134] At a step S56, the generating unit 131 in the noise envelope
information decoding unit 104 generates the noise signal for each
band at the high frequency side, on the basis of the noise envelope
information, and supplies this to the band pass combination filter
106. That is to say, the generating unit 131 generates the noise
signal by adjusting the gain for each zone of a predetermined
signal which has been divided into zones by the noise boundary
position represented by the noise envelope information so that the
gain of this signal matches the gain represented by the noise
envelope information.
[0135] At a step S57, the sine wave information decoding unit 105
decodes the sine wave information from the encoding stream decoding
unit 101. For example, the information representing the combination
start position included in the sine wave information is decoded as
necessary.
[0136] At a step S58, the sine wave information decoding unit 105
performs the sine wave signal generation processing to generate the
sine wave signal for each band at the high frequency side, and
supplies this to the band pass combination filter 106. Further, the
details of the sine wave signal generation processing will be
described later.
[0137] At a step S59, the band pass combination filter 106 combines
the bands of the low frequency signal from the low frequency
decoding unit 102, the pseudo high frequency signal from the
envelope information decoding unit 103, the noise signal from the
noise envelope information decoding unit 104, and the sine wave
signal from the sine wave information decoding unit 105.
[0138] That is to say, the audio signal is generated by performing
the band combination by adding the samples at each timing from the
low frequency signal, the pseudo high frequency signal for each
band, the noise signal for each band, and the sine wave signal for
each band input from the low frequency decoding unit 102 through
the sine wave information decoding unit 105. Here, the signal made
up of the pseudo high frequency signal, the noise signal, and the
sine wave signal is the high frequency component obtained by
prediction.
[0139] When the audio signal has been obtained by the band
combination, the band pass combination filter 106 outputs this
audio signal to a downstream player unit or similar, and the
decoding processing terminates. This decoding processing is
performed per frame, and as the next frame of the encoding stream
is input, the decoding device 91 performs the decoding processing
on this frame of the encoding stream.
[0140] In this way, the decoding device 91 predicts the high
frequency components on the basis of the low frequency signal, the
envelope information, the noise envelope information, and the sine
wave information, and generates the audio signal by expanding the
bands from the high frequency signal obtained by prediction and the
decoded low frequency signal. At this time, by using the sine wave
information representing a more accurate combination start position
of the sine wave signal, a more accurate sine wave signal
combination may be performed, and so audio at a higher audio
quality may be obtained.
[Description of the Sine Wave Signal Generation Processing]
[0141] Next, the sine wave signal generation processing
corresponding to step S58 of the processing in FIG. 6 will be
described with reference to the flowchart in FIG. 7.
[0142] At a step S81, the generating unit 141 in the sine wave
information decoding unit 105 determines whether or not the start
timing for the sine wave signal combination processing has passed
based on the combination start position and the information
included in the sine wave information representing whether or not
the sine wave signal has been detected.
[0143] For example, the generating unit 141 generates the sine wave
signal as the sine wave component configuring the high frequency
component by designating the beginning of the frame as the
emergence start position and the end of the frame as the emergence
end position.
[0144] Here, the frequency of the sine wave signal designated as
the sine wave component configuring the high frequency component is
identified by the information included in the sine wave information
representing whether or not the sine wave signal has been detected.
Also, the amplitude of the sine wave signal frequency identified by
the sine wave information is identified from the envelope
information supplied from the envelope information decoding unit
103 through the sine wave information decoding unit 105. For
example, the generating unit 141 converts the envelope information
into frequencies, and obtains the amplitude of the sine wave signal
based on the power of the sine wave signal frequency from among the
power of all frequencies obtained as a result.
[0145] Next, the generating unit 141 selects the sample in the
start position of the timeslot for one frame of the sine wave
signal as the sample (timeslot) to be processed in order from the
beginning of the frame. Then, the generating unit 141 determines
whether or not the selected sample position is the sample position
represented by the combination start position, that is to say the
timing at which the combination of the sine wave signal should be
started. For example, when information included in the sine wave
information indicates that the sine wave signal has not been
detected, this will continue to be determined that the start timing
of the sine wave combination processing has not passed.
[0146] When it has been determined that the start timing has not
passed at the step S81, at a step S82, the generating unit 141
shifts the generated sine wave signal backward on a timeline by one
timeslot. As a result, the emergence start position of the sine
wave signal is shifted backward on a timeline. When the shifting of
the sine wave signal is performed, the sine wave has not yet
emerged in the timeslot zone to be processed, and so the sine wave
signal is not output from the sine wave information decoding unit
105 to the band pass combination filter 106.
[0147] At a step S83, the generating unit 141 determines whether or
not the end of one frame has been reached. For example, when the
zone for the final timeslot configuring the frame is being
processed, that is to say, when all timeslots in the frame have
been processed, this is determined that the end of the frame has
been reached.
[0148] When it has been determined that the end of the frame has
not been reached at the step S83, the next timeslot is selected as
that to be processed, the processing returns to step S81, and the
previously described processing repeats. In this case, the shit
processing, etc. is performed on the sine wave signal already
generated.
[0149] Conversely, when it has been determined that the end of the
frame has been reached at the step S83, the sine wave signal
generation processing terminates, and afterwards, the processing
proceeds to a step S59 in FIG. 6. In this case, the result is that
the sine wave signal combination is not performed.
[0150] Also, when it has been determined that the start position of
the sine wave combination processing has passed at the step S81, at
a step S84, the generating unit 141 performs the sine wave
combination processing. That is to say, the generating unit 141
outputs to the band pass combination filter 106 the sample value
configuring the timeslot being processed of the sine wave signal
which has been arbitrarily shift processed. As a result, the sample
value of the output sine wave signal sample is combined with the
low frequency signal as the sine wave component configuring the
high frequency component.
[0151] At a step S85, the generating unit 141 determines whether or
not the end of one frame has been reached. For example, when the
zone for the final timeslot configuring the frame is being
processed, that is to say, when all timeslots in the frame have
been processed, this is determined that the end of the frame has
been reached.
[0152] When it has been determined that the end of the frame has
not been reached at the step S85, the next timeslot is selected as
that to be processed, the processing returns to step S84, and the
previously described processing repeats. Conversely, when it has
been determined that the end of the frame has been reached at the
step S85, the sine wave signal generation processing terminates,
and afterwards, the processing proceeds to the step S59 in FIG.
6.
[0153] In this way, the sine wave information decoding unit 105
shifts the emergence start position of the sine wave signal to the
combination start position on the basis of the sine wave
information, and outputs the shifted sine wave signal. As a result,
the combination of the sine wave is started at a more accurate
position in one frame, and so audio at a higher audio quality may
be obtained.
Second Embodiment
[Configuration Example of Encoding Device]
[0154] Though it has been described above that the combination
start position representing the time (number of samples) from the
beginning position of the frame until the position at which the
combination of the sine wave signal should start is included in the
sine wave information, information of the difference between the
combination start position and the noise boundary position may be
included.
[0155] In this case, the encoding device is configured as
illustrated in FIG. 8. Further, the components in FIG. 8 that
correspond to those in FIG. 1 have the same reference numerals, and
so their descriptions will be omitted as appropriate. An encoding
device 171 in FIG. 8 and the encoding device 11 are different in
that a difference calculating unit 181 is newly provisioned in the
sine wave information generating unit 26 of the encoding device
171, and so are the same regarding other components.
[0156] The difference calculating unit 181 in the sine wave
information generating unit 26 calculates the difference between
the combination start position of the sine wave signal detected by
the position detection unit 62 and the noise boundary position. The
sine wave information generating unit 26 supplies information made
up from the difference information representing the difference with
the noise boundary position calculated by the difference
calculating unit 181 and the information representing whether or
not the sine wave signal has been detected to the encoding stream
generating unit 27 as the sine wave information.
[Description of Encoding Processing]
[0157] Next, the encoding processing performed by the encoding
device 171 will be described with reference to the flowchart in
FIG. 9. Further, the processing of the step S111 through the step
S118 are the same as the step S11 through the step S18 in FIG. 2,
and so their description is omitted.
[0158] At a step S119, the boundary calculating unit 52 in the
noise envelope information generating unit 25 detects the noise
boundary position for each band at the high frequency side. Then,
at a step S20, the noise envelope information generating unit 25
generates the noise envelope information for each band at the high
frequency side, and supplies this to the encoding stream generating
unit 27. Further, at the step S119 and step S120, the same
processing as at step S20 and step S21 in FIG. 2 is performed.
[0159] At a step S121, the difference calculating unit 181 in the
sine wave information generating unit 26 calculates the difference
between the noise boundary position and the combination start
position of the sine wave signal detected by the position detection
unit 62.
[0160] For example, as illustrated in FIG. 10, the time (number of
samples) from the start position of the sine wave combination until
the noise boundary position is calculated as the difference.
Further, the horizontal axis in the figure represents the timeline.
Also, an arrow FS11 and an arrow FE11 in FIG. 10 represent the
start position and the end position of the frame, respectively.
[0161] According to the example in FIG. 10, the position
represented by an arrow N11 in the frame represents the noise
boundary position. Also, the combination start position of the sine
wave signal is the position represented by an arrow G11, and the
combination start position is positioned before the noise boundary
position. Therefore, the sine wave signal is combined in the zone
from the combination start position represented by the arrow G11
until the end position of the frame.
[0162] According to this example, the length of time (temporal
distance) from the combination start position represented by the
arrow G11 until the noise boundary position represented by the
arrow N11 is designated as the difference information with the
noise boundary position. Here, the time from the combination start
position until the noise boundary position is an integral multiple
of the timeslot length.
[0163] By using the difference information representing the time
from the combination start position until the noise boundary
position obtained in this way, a more accurate combination start
position may also be identified at the decoding side of the audio
signal, and so audio at a higher audio quality may be obtained.
[0164] Returning to the description of the flowchart in FIG. 9,
after the difference information with the noise boundary position
is obtained at the step S121, the processing proceeds to a step
S122.
[0165] At a step S122, the sine wave information generating unit 26
generates the sine wave information for each band at the high
frequency side, and supplies this to the encoding stream generating
unit 27.
[0166] For example, the sine wave information generating unit 26
designates the information made up from the information
representing whether or not the sine wave has been detected from
the high frequency band and the difference information between the
combination start position and the noise boundary position as the
sine wave information. At this time, the encoding unit 63 in the
sine wave information generating unit 26 performs the variable
length encoding of the difference information with the noise
boundary position. The sine wave information generating unit 26
supplies the sine wave information made up from the difference
information processed by the variable length encoding and the
information representing whether or not the sine wave signal has
been detected to the encoding stream generating unit 27.
[0167] After the sine wave information is generated, the processing
at a step S123 is performed and the encoding processing terminates,
and as the processing at the step S123 is the same as the
processing at the step S22 in FIG. 2, so its description is
omitted.
[0168] As previously described, the encoding device 171 generates
and outputs the encoding stream made up from the low frequency
signal, the envelope information, the noise envelope information,
and the sine wave information. At this time, by detecting a more
accurate combination start position of the sine wave signal and
generating sine wave information including the difference
information used for identifying this combination start position, a
more accurate combination of the sine wave signal may be performed
during decoding, and so audio at a higher audio quality may be
obtained as a result.
[Configuration Example of Decoding Device]
[0169] Also, a decoding device that receives the encoding stream
transmitted from the encoding device 171, and obtains the audio
signal from the encoding stream is configured as illustrated in
FIG. 11. Further, the components in FIG. 11 that correspond to
those in FIG. 5 have the same reference numerals, and so their
descriptions will be omitted as appropriate. A decoding device 211
in FIG. 11 and the decoding device 91 are different in that a
position calculating unit 221 is newly provisioned in the sine wave
information decoding unit 105 of the decoding device 211, and so
are the same regarding other components.
[0170] The position calculating unit 221 in the decoding device 211
calculates the combination start position of the sine wave signal
from the difference information obtained from the sine wave
information and the noise boundary position supplied from the noise
envelope information decoding unit 104.
[Description of Decoding Processing]
[0171] Next, the decoding processing performed by the decoding
device 211 will be described with reference to the flowchart in
FIG. 12. Note that, the processing from step S151 through step S157
is the same as the processing from step S51 through step S57 in
FIG. 6, and so their descriptions are omitted. However, at the step
S155, the noise envelope information decoding unit 104 supplies the
information representing the noise boundary position included in
the noise envelope information obtained from the decoding to the
sine wave information decoding unit 105.
[0172] At a step S158, the sine wave information decoding unit 105
performs the sine wave signal generation processing, generates the
sine wave signal for each band at the high frequency side, and
supplies this to the band pass combination filter 106. Further,
details of the sine wave signal generation processing will be
described later.
[0173] After the sine wave signal generation processing has been
performed, the processing at a step S159 is performed, and the
decoding processing terminates, and as the processing at the step
S159 is the same as the step S59 in FIG. 6, its description will be
omitted.
[Description of Sine Wave Signal Generation Processing]
[0174] Also, at the step S158 in FIG. 12, the sine wave information
decoding unit 105 performs the sine wave signal generation
processing illustrated in FIG. 13. Hereafter, the sine wave signal
generation processing corresponding to the processing at the step
S158 will be described with reference to the flowchart in FIG.
13.
[0175] At a step S181, the position calculating unit 221 in the
sine wave information decoding unit 105 calculates the combination
start position of the sine wave signal from the noise boundary
position supplied from the noise envelope information decoding unit
104 and the difference information obtained from the sine wave
information. That is to say, the difference in the time between the
combination start position and the noise boundary position is
subtracted from the time from the start position of the frame being
processed until the noise boundary position, the time from the
start position of the frame until the combination start position of
the sine wave signal is obtained, and the timing (sample) of the
combination start position is identified.
[0176] After the combination start position is calculated, the
processing of a step S182 through a step S186 is performed, and the
sine wave signal generation processing terminates, and as this
processing is the same as the processing of the step S81 through
the step S85 in FIG. 7, their descriptions are omitted. After the
sine wave signal generation processing terminates in this way, the
processing proceeds to a step S159 in FIG. 12.
[0177] In this way, the sine wave information decoding unit 105
calculates a more accurate combination start position of the sine
wave signal from the difference information included in the sine
wave information signal and the noise boundary position. As a
result, the combination of the sine wave signal is started at a
more accurate position in one frame, and so audio at a higher audio
quality may be obtained.
Third Embodiment
[Configuration Example of Encoding Device]
[0178] Though the second Embodiment has been described above with
an example in which the difference information between the
combination start position and the noise boundary position is
included in the sine wave information, information of the
difference between the peak position of the combination start
position and the high frequency signal envelope may be
included.
[0179] In this case, the encoding device is configured as
illustrated in FIG. 14. Further, the components in FIG. 14 that
correspond to those in FIG. 1 have the same reference numerals, and
so their descriptions will be omitted as appropriate. An encoding
device 251 in FIG. 14 and the encoding device 11 are different in
that a peak detection unit 261 and a difference calculating unit
262 are newly provisioned in the sine wave information generating
unit 26 of the encoding device 251, and so are the same regarding
other components.
[0180] According to the encoding device 251, the envelope
information supplied from the envelope information generating unit
24 to the noise envelope information generating unit 25 is also
supplied from the noise envelope information generating unit 25 to
the sine wave information generating unit 26. The peak detection
unit 261 detects the peak position of the high frequency signal
envelope on the basis of the envelope information supplied from the
noise envelope information generating unit 25.
[0181] The difference calculating unit 262 calculates the
difference between the combination start position of the sine wave
signal detected by the position detection unit 62 and the peak
position of the high frequency signal envelope. The sine wave
information generating unit 26 supplies the information made up
from the difference information representing the difference with
the peak position calculated by the difference calculating unit 262
and the information representing whether or not the sine wave
signal has been detected to the encoding stream generating unit 27
as the sine wave information.
[Description of Encoding Processing]
[0182] Next, the encoding processing performed by the encoding
device 251 will be described with reference to the flowchart in
FIG. 15. Further, the processing of the step S211 through the step
S218 are the same as the step S11 through the step S18 in FIG. 2,
and so their description is omitted. However, at the step S214, the
generated envelope information is also supplied to the sine wave
information generating unit 26 from the envelope information
generating unit 24 through the noise envelope information
generating unit 25.
[0183] At a step S219, the peak detection unit 261 in the sine wave
information generating unit 26 detects the peak position of the
high frequency signal envelope on the basis of the envelope
information supplied from the noise envelope information generating
unit 25. For example, the position where the gain of the high
frequency signal envelope represented by the envelope information
is at a maximum is detected as the peak position of the high
frequency signal envelope.
[0184] At a step S220, the difference calculating unit 262
calculates, for each band at the high frequency side, the
difference between the combination start position of the sine wave
signal detected by the position detection unit 62 and the peak
position of the envelope detected by the peak detection unit
261.
[0185] For example, as illustrated in FIG. 16, the time (number of
samples) from the start position of the sine wave combination until
the peak position is calculated as the difference. Further, the
horizontal axis in the figure represents the timeline. Also, an
arrow FS21 and an arrow FE21 in FIG. 16 represent the start
position and the end position of the frame, respectively.
[0186] According to the example in FIG. 16, the envelope of the
high frequency signal is represented by a dotted line, and the
position represented by an arrow P1 in the frame represents the
peak position of this envelope. Also, the combination start
position of the sine wave signal is the position represented by an
arrow G21, and the combination start position is positioned before
the peak position of the envelope. During the decoding, the sine
wave signal is combined in the zone from the combination start
position represented by the arrow G21 until the end position of the
frame.
[0187] According to this example, the length of time (temporal
distance) from the combination start position represented by the
arrow G21 until the peak position of the high frequency signal
envelope represented by the arrow P1 is designated as the
difference with the peak position. Here, the time from the
combination start position until the peak position is an integral
multiple of the timeslot length.
[0188] By using the difference information representing the time
from the combination start position until the peak position
obtained in this way, a more accurate combination start position
may be identified during decoding of the audio signal, and so audio
at a higher audio quality may be obtained.
[0189] Returning to the description of the flowchart in FIG. 15,
after the difference information with the peak position is obtained
at the step S220, the processing proceeds to a step S221.
[0190] At the step S221, the sine wave information generating unit
26 generates the sine wave information for each band at the high
frequency side, and supplies this to the encoding stream generating
unit 27.
[0191] For example, the sine wave information generating unit 26
designates the information made up from the information
representing whether or not the sine wave has been detected from
the high frequency band and the difference information between the
combination start position and the peak position as the sine wave
information. At this time, the encoding unit 63 in the sine wave
information generating unit 26 performs the variable length
encoding of the difference information with the peak position. The
sine wave information generating unit 26 supplies the sine wave
information made up from the difference information processed by
the variable length encoding and the information representing
whether or not the sine wave signal has been detected to the
encoding stream generating unit 27.
[0192] After the sine wave information is generated, the processing
at a step S222 through a step S224 is performed and the encoding
processing terminates, and as this processing is the same as the
processing at the step S20 through the step S22 in FIG. 2, so its
description is omitted.
[0193] As previously described, the encoding device 251 generates
and outputs the encoding stream made up from the low frequency
signal, the envelope information, the noise envelope information,
and the sine wave information. At this time, by detecting a more
accurate combination start position of the sine wave signal and
generating sine wave information including the difference
information used for identifying this combination start position, a
more accurate combination of the sine wave signal may be performed
during decoding, and so audio at a higher audio quality may be
obtained as a result.
[Configuration Example of Decoding Device]
[0194] Also, a decoding device that receives the encoding stream
transmitted from the encoding device 251, and obtains the audio
signal from the encoding stream is configured as illustrated in
FIG. 17. Further, the components in FIG. 17 that correspond to
those in FIG. 5 have the same reference numerals, and so their
descriptions will be omitted as appropriate. A decoding device 301
in FIG. 17 and the decoding device 91 are different in that a
position calculating unit 311 is newly provisioned in the sine wave
information decoding unit 105 of the decoding device 301, and so
are the same regarding other components.
[0195] The position calculating unit 311 in the decoding device 301
calculates the combination start position of the sine wave signal
from the difference information obtained from the sine wave
information and the envelope information supplied from the envelope
information decoding unit 103.
[Description of Decoding Processing]
[0196] Next, the decoding processing performed by the decoding
device 301 will be described with reference to the flowchart in
FIG. 18. Further, the processing of a step S251 through a step S257
are the same as the step S51 through the step S57 in FIG. 6, and so
their description is omitted.
[0197] At a step S258, the sine wave information decoding unit 105
performs the sine wave signal generation processing, generates the
sine wave signal for each band at the high frequency side, and
supplies this to the band pass combination filter 106. Further,
details of the sine wave signal generation processing will be
described later.
[0198] After the sine wave signal generation processing has been
performed, the processing at a step S259 is performed, and the
decoding processing terminates, and as the processing at the step
S259 is the same as the step S59 in FIG. 6, its description is
omitted.
[Description of Sine Wave Signal Generation Processing]
[0199] Also, at the step S258 in FIG. 18, the sine wave information
decoding unit 105 performs the sine wave signal generation
processing illustrated in FIG. 19. Hereafter, the sine wave signal
generation processing corresponding to the processing at the step
S258 will be described with reference to the flowchart in FIG.
19.
[0200] At a step S281, the position calculating unit 311 in the
sine wave information decoding unit 105 calculates the combination
start position of the sine wave signal from the envelope
information supplied from the envelope information decoding unit
103 and the difference information obtained from the sine wave
information.
[0201] That is to say, the position where the gain of the high
frequency signal envelope represented in the envelope information
is at a maximum is calculated by the position calculating unit 311
as the peak position of the high frequency signal envelope. Then,
the position calculating unit 311 subtracts the difference in the
time between the combination start position and the peak position
is subtracted from the time from the start position of the frame
being processed until the peak position, the time from the start
position of the frame until the combination start position of the
sine wave signal, and the timing (sample) of the combination start
position is identified.
[0202] After the combination start position is calculated, the
processing of a step S282 through a step S286 is performed, and the
sine wave signal generation processing terminates, and as this
processing is the same as the processing of the step S81 through
the step S85 in FIG. 7, their descriptions are omitted. After the
sine wave signal generation processing terminates in this way, the
processing proceeds to a step S259 in FIG. 18.
[0203] In this way, the sine wave information decoding unit 105
calculates a more accurate combination start position of the sine
wave signal from the difference information included in the sine
wave information and the peak position of the high frequency signal
envelope. As a result, the combination of the sine wave signal is
started at a more accurate position in one frame, and so audio at a
higher audio quality may be obtained.
[0204] Further, though an example has been described above in which
the detection of the peak position of the envelope is performed at
the decoding device 301 side, information representing the peak
position may be included in the sine wave information. In this
case, the sine wave information generating unit 26 in the encoding
device 251 generates the sine wave information including the
information representing the peak position, and the position
calculating unit 311 in the decoding device 301 calculates the
combination start position from the difference information and the
information representing the peak position included in the sine
wave information.
Fourth Embodiment
[Configuration Example of Encoding Device]
[0205] Though an example has been described above that the sine
wave information included one type of previously determined
information from among the combination start position, the
difference information with the noise boundary position, or the
difference information with the peak position, the information
among these with the smallest encoding amount may be selected to be
included in the sine wave information.
[0206] In this case, the encoding device is configured as
illustrated in FIG. 20, for example. Further, the components in
FIG. 20 that correspond to those in FIG. 1 or FIG. 14 have the same
reference numerals, and so their descriptions will be omitted as
appropriate. An encoding device 341 in FIG. 20 and the encoding
device 11 in FIG. 1 are different in that a peak detection unit
261, a difference calculating unit 351, and a selection unit 352
are newly provisioned in the sine wave information generating unit
26 of the encoding device 341, and so are the same regarding other
components.
[0207] According to the encoding device 341, the envelope
information supplied from the envelope information generating unit
24 to the noise envelope information generating unit 25 is also
supplied from the noise envelope information generating unit 25 to
the sine wave information generating unit 26, and the peak
detection unit 261 detects the peak position of the high frequency
signal envelope on the basis of the envelope information.
[0208] The difference calculating unit 351 calculates the
difference between the combination start position of the sine wave
signal detected by the position detection unit 62 and the peak
position of the high frequency signal envelope. The difference
calculating unit 351 also calculates the difference between the
combination start position and the noise boundary position.
[0209] The selection unit 352 selects the information that will
result in the smallest encoding amount after the variable length
encoding from among the combination start position, the difference
information with the peak position, or the difference information
with the noise boundary position. The sine wave information
generating unit 26 supplies the information made up from the
information representing the result of the selection by the
selection unit 352, the information selected by the selection unit
352, and the information representing whether or not the sine wave
signal has been detected, to the encoding stream generating unit 27
as sine wave information.
[Description of Encoding Processing]
[0210] Next, the encoding processing performed by the encoding
device 341 will be described with reference to the flowchart in
FIG. 21. Further, the processing of the step S311 through the step
S321 are the same as the step S111 through the step S121 in FIG. 9,
and so their description is omitted.
[0211] However, at the step S321, the difference calculating unit
351 in the sine wave information generating unit 26 calculates the
difference between the combination start position of the sine wave
signal detected by the position detection unit 62 and the noise
boundary position for each band at the high frequency side. Also,
at the step S314, the generated envelope information is also
supplied to the sine wave information generating unit 26 from the
envelope information generating unit 24 through the noise envelope
information generating unit 25.
[0212] At a step S322, the peak detection unit 261 in the sine wave
information generating unit 26 detects, for each band at the high
frequency side, the peak position of the high frequency signal
envelop on the basis of the envelop information supplied from the
noise envelope information generating unit 25.
[0213] At a step S323, the difference calculation unit 351
calculates, for each band at the high frequency side, the
difference between the combination start position of the sine wave
signal detected by the position detection unit 62 and the peak
position of the envelope detected by the peak detection unit
261.
[0214] Further, the same processing at the step S219 and the step
S220 in FIG. 15 is performed at the step S322 and the step
S323.
[0215] At a step S324, the selection unit 352 selects, for each
band at the high frequency side, the information that will result
in the smallest encoding amount after the variable length encoding
from among the combination start position, the difference
information between the combination start position and the peak
position, or the difference information between the combination
start position and the noise boundary position. Then, the selection
unit 352 generates the selection information representing the
result of this selection. At this time, only the encoding amount of
the combination start position or similar may be calculated and
compared, or the actual combination start position or similar
information may be processed by the variable length encoding, and
this encoding amount may be compared.
[0216] At the step S325, the sine wave information generating unit
26 generates the sine wave information for each band at the high
frequency side, and supplies this to the encoding stream generating
unit 27.
[0217] Specifically, the sine wave information generating unit 26
designates the information made up from the information
representing whether or not the sine wave signal has been detected
from the high frequency band, the selection information, and the
information representing the selection information as the sine wave
information. At this time, the encoding unit 63 in the sine wave
information generating unit 26 performs the variable length
encoding of the selection information and the information
representing the selection information. The sine wave information
generating unit 26 supplies the sine wave information made up from
the selection information and the information representing the
selection information processed by the variable length encoding and
the information representing whether or not the sine wave signal
has been detected to the encoding stream generating unit 27.
[0218] For example, when the information representing the selection
information is the difference information between the combination
start position and the peak position, the information made up from
the selection information, the difference information with the peak
position, and the information representing whether or not the sine
wave signal has been detected is designated as the sine wave
information. In this way, by generating the sine wave information
including the information with the smallest encoding amount that
identifies the combination start position of the sine wave signal,
the encoding amount of the encoding stream may be further
reduced.
[0219] After the sine wave information is generated, the processing
at a step S326 is performed and the encoding processing terminates,
and as this processing is the same as the processing at the step
S224 in FIG. 15, its description is omitted.
[0220] As previously described, the encoding device 341 generates
and outputs the encoding stream made up from the low frequency
signal, the envelope information, the noise envelope information,
and the sine wave information. At this time, by generating the sine
wave information including the information with the smallest
encoding amount from among the information that identifies the
combination start position of the sine wave signal, the data amount
of the encoding stream to be transferred may be reduced, and at the
same time, a more accurate combination of the sine wave signal may
be performed during decoding at the decoding side of the audio
signal. As a result, audio at a higher audio quality may be
obtained.
[Configuration Example of Decoding Device]
[0221] Also, a decoding device that receives the encoding stream
transmitted from the encoding device 341, and obtains the audio
signal from the encoding stream is configured as illustrated in
FIG. 22, for example. Further, the components in FIG. 22 that
correspond to those in FIG. 5 have the same reference numerals, and
so their descriptions will be omitted as appropriate. A decoding
device 381 in FIG. 22 and the decoding device 91 are different in
that a position calculating unit 391 is newly provisioned in the
sine wave information decoding unit 105 of the decoding device 381,
and so are the same regarding other components.
[0222] The position calculating unit 391 in the decoding device 381
calculates the combination start position of the sine wave signal
from either the difference information with the peak position or
the difference information with the noise boundary position
obtained from the sine wave information, depending on the selection
information included in the sine wave information.
[Description of Decoding Processing]
[0223] Next, the decoding processing performed by the decoding
device 381 will be described with reference to the flowchart in
FIG. 23. Further, the processing of a step S351 through a step S356
are the same as the step S51 through the step S56 in FIG. 6, and so
their description is omitted.
[0224] However, at the step 355, the noise envelope information
decoding unit 104 supplies the information representing the noise
boundary position included in the noise envelope information
obtained by the decoding to the sine wave information decoding unit
105.
[0225] At a step S357, the sine wave information decoding unit 105
decodes the sine wave information from the encoding stream decoding
unit 101. For example, the selection information included in the
sine wave information, and the information used to obtain the
combination start position identified by the selection information,
are decoded.
[0226] At a step S358, the sine wave information decoding unit 105
performs the sine wave signal generation processing, generates the
sine wave signal for each band at the high frequency side, and
supplies this to the band pass combination filter 106. Further,
details of the sine wave signal generation processing will be
described later.
[0227] After the sine wave signal generation processing has been
performed, the processing at a step S359 is performed, and the
decoding processing terminates, and as the processing at the step
S359 is the same as the step S59 in FIG. 6, its description is
omitted.
[Description of Sine Wave Signal Generation Processing]
[0228] Also, at the step S358 in FIG. 23, the sine wave information
decoding unit 105 performs the sine wave signal generation
processing illustrated in FIG. 24. Hereafter, the sine wave signal
generation processing corresponding to the processing at the step
S358 will be described with reference to the flowchart in FIG.
24.
[0229] At a step S381, the position calculating unit 391 determines
whether or not the information used to obtain the combination start
position of the sine wave signal represented by the selection
information is the information actually representing the
combination start position. That is to say, it is determined
whether or not the combination start position is included in the
sine wave information.
[0230] In the event that determination is made in step S381 that
the information represented by the selection information is the
information representing the combination start position of the sine
wave signal, the processing proceeds to a step S385.
[0231] Conversely, in the event that determination is made in step
S381 that the information represented by the selection information
is not be the information representing the combination start
position of the sine wave signal, the processing proceeds to a step
S382.
[0232] At the step S382, the position calculating unit 391
determines whether or not the information used to obtain the
combination start position of the sine wave signal represented by
the selection information is the difference information between the
combination start position and the noise boundary position. That is
to say, it is determined whether or not the difference information
with the noise boundary position is included in the sine wave
information.
[0233] When the information represented by the selection
information is determined to be the difference information with the
noise boundary position, the processing proceeds to a step
S383.
[0234] At the step S383, the position calculating unit 391 in the
sine wave information decoding unit 105 calculates the combination
start position of the sine wave signal from the noise boundary
position supplied from the noise envelope information decoding unit
104 and the difference information with the noise boundary position
obtained from the sine wave information. After the combination
start position is calculated, the processing proceeds to the step
S385.
[0235] Also, when the information represented by the selection
information is determined to not be the difference information with
the noise boundary position in the step S382, that is to say, when
the information represented by the selection information is the
difference information between the combination start position and
the peak position, the processing proceeds to a step S384.
[0236] At the step S384, the position calculating unit 391 in the
sine wave information decoding unit 105 calculates the combination
start position of the sine wave signal form the envelope
information supplied from the envelope information decoding unit
103 and the difference information with the peak position of the
high frequency signal envelope obtained from the sine wave
information.
[0237] That is to say, the position calculating unit 391 detects
the position where the gain in the high frequency signal envelope
represented by the envelope information is at a maximum as the peak
position of the high frequency signal envelope. Then, the position
calculating unit 391 subtracts the difference in time between the
combination start position and the peak position from the time from
the start position of the frame to be processed until the peak
position, obtains the time from the start position of the frame
until the combination start position of the sine wave signal, and
identifies the timing (sample) of the combination start position.
After the combination start position is calculated, the processing
proceeds to the step S385.
[0238] After the information represented by the selection
information is determined to be the information representing the
combination start position at the step S381, or the combination
start position is calculated at the step S383, or the combination
start position is calculated at the step S384, the processing
proceeds to the step S385. Then, the processing of the step S382
through a step S389 is performed, and the sine wave signal
generation processing terminates, and as this processing is the
same as the processing of the step S81 through the step S85 in FIG.
7, their descriptions are omitted. After the sine wave signal
generation processing terminates in this way, the processing
proceeds to a step S359 in FIG. 23.
[0239] In this way, the sine wave information decoding unit 105
identifies the information included in the sine wave information
from the selection information, and arbitrarily calculates a more
accurate combination start position of the sine wave signal
according to the result of this specification. As a result, the
combination of the sine wave signal is started at a more accurate
position in one frame, and so audio at a higher audio quality may
be obtained.
[0240] The series of processing previously described may be
executed by hardware, or may be executed by software. When the
series of processing is executed by software, a program configuring
this software may be installed into a computer built with
specialized hardware, or by installing various programs from a
program recording medium into a general purpose personal computer,
for example, that may execute various functions.
[0241] FIG. 25 is a block diagram illustrating a configuration
example of computer hardware for executing the previously described
series of processing as a program.
[0242] A CPU 501, ROM (Read Only Memory) 502, and RAM (Random
Access Memory) 503, are connected together in the computer by a bus
504.
[0243] Also, an input/output interface 505 is connected to the bus
504. Devices connected to the input/output interface 505 include an
input unit 506 made up of a keyboard, a mouse, a microphone, etc.,
an output unit 507 made up of a display, speaker, etc., a recording
unit 508 made up of a hard disk, non-volatile memory, etc., a
communication unit 509 made up of a network interface, etc., and a
drive 510 for driving a magnetic disk, an optical disk, a
magneto-optical disk, or a removable media 511 such as
semiconductor memory.
[0244] According to the computer configured in this way, the CPU
501 loads and executes the program installed in the recording unit
508 into the RAM 503 through the input/output interface 505 and bus
504, for example, to perform the previously described series of
processing.
[0245] The program executed by the computer (CPU 501) may be
recorded in the removable media 511, which is a form of packaged
media configured of, for example, a magnetic disk (including a
floppy disk), an optical disk (such as CD-ROM (Compact Disc-Read
Only Memory) or DVD (Digital Versatile Disc)), a magneto-optical
disk, or semiconductor memory, etc., or may be supplied via a wired
or wireless transmission medium such as a local area network, the
Internet, or a digital satellite broadcast.
[0246] Also, the program may be installed to the recording unit 508
through the input/output interface 505 by installing the removable
media 511 to the drive 510. Also, the program may be installed to
the recording unit 508 after being received by the communication
unit 509 via the wired or wireless transfer medium. Also, the
program may be previously installed in the ROM 502 or the recording
unit 508.
[0247] Further, the program executed by the computer may perform
the processing in time-sequence order as described in the present
specification, may perform the processing in parallel, or at a
necessary timing such as when a call is performed.
[0248] Further, the embodiments of the preset technology are not
limited to the previously described embodiments, and various
modifications may occur insofar as they are within the scope of the
present technology.
REFERENCE SIGNS LIST
[0249] 11 encoding device [0250] 22 low frequency encoding unit
[0251] 24 envelope information generating unit [0252] 25 noise
envelope information generating unit [0253] 26 sine wave
information generating unit [0254] 52 boundary calculating unit
[0255] 61 sine wave detection unit [0256] 62 position detection
unit [0257] 91 decoding device [0258] 102 low frequency decoding
unit [0259] 103 envelope information decoding unit [0260] 104 noise
envelope information decoding unit [0261] 105 sine wave information
decoding unit [0262] 141 generating unit [0263] 181 difference
calculating unit [0264] 221 position calculating unit [0265] 261
peak detection unit [0266] 262 difference calculating unit [0267]
311 position detecting unit [0268] 351 difference calculating unit
[0269] 352 selection unit [0270] 391 position calculating unit
* * * * *