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United States Patent [19]
{11] Patent Number:
Kim
[45]
[54]
5,546,465
Date of Patent:
Aug. 13, 1996
AUDIO PLAYBACK APPARATUS AND
Primary Examiner?Forestcr w. lsen
METHOD
Attorney, Agent, or Firmevsughrue, Mion, Zinn, Maepeak &
Seas
[75] Inventor: Jae-young Kim, Suwon, Rep. of Korea
[57]
[73]
Assignee: Samsung Electronics Co. Ltd.,
ABSTRACT
_
Kyungkidm Rep. of Korea
_
All-311K110 playback apparatus and method are disclosed
WhlCh includes a Dolby pro-logic decoder for converting a
,
[211
[22]
digital audio signal into a left signal, a right signal, a center
Appl' No" 341922
Filed:
Nov. 16, 1994
_
[30]
_
signal, and a surround signal; a sound ?eld processor for
convening the left, right, center and surround signals into a
‘
_
'
front left signal, a front right signal, a rear left signal, and a
Fore'g" Apphcamm Pnonty Data
Nov. 18, 1993
[KR]
rear right signal; an audio processor for mixing the left,
Rep. ofKorea .................... .. 93-24617
6
Illl. Cl.
[521
158]
right‘ from 16ft, from right, rear 10“ and war right Signals
according to a predetermined relationship equation and
...................................................... ..
converting them into signals for two channels Composed of
US. Cl. ................................ .. 381/18; 381/63; 381/17
Field of Search ................................ .. 381/17, 22, 23,
3 left-speaker output signal and a right-speaker output
signal; and audio output means for outputting the left
381/63, 18
speaker output signal via a left speaker, the right-speaker
156]
output signal via a right speaker, and the center signal via a
central speaker. thereby allowing a listener to feel a rich
References Cited
UIS- PATENT DOCUMENTS
sound presence even with fewer output speakers then Wllh
conventional audio playback apparatuses.
5,261,005
11/1993
5,436,975
5,459,790
7/1995 Lowe et a1.
381/63
10/1995 Sco?eld et a1. ......................... .. 381/25
Masayuki ................................ .. 381/18
21
s
9 Claims, 4 Drawing Sheets
22
L
S
8
23
FL
S
5
DOLBY
R
PR0-
SC
SOUND
RL CHANNEL
' LOGIC
s
FIELD
s SOUND
HELD
RR
AUDIO
SIGNAL DECODER 5
S
FSR Two._
PROCESSOR
5 PROCESSOR
EL
24
3
,+,
ER
L+EL
25
+
R+ER
US. Patent
Aug. 13, 1996
Sheet 1 of 4
5,546,465
FIG. 1 (PRIOR ART)
:L
1&1
LR
L
DOLBY
AUDIO
PRO-
SIGNAL
LOGIC
R
____ FL
SOUND
____. FR
HELD
C
1. PROCESSOR ———- RL
5
———- RR
DECODER
\ 12
US. Patent
Aug. 13, 1996
Sheet 2 of 4
5,546,465
FIG.2
21
g
DOLBY
__.."R°
AUDIO
_
LOG'C
22
|_
s
23
5
FL
8
SR
C
S
$
EL
FSR Two_
SOUND
FIELD
R'
3
+
L+EL
CHANNEL
PROCESSOR S SOUND
SIGNAL DE°°°ER 5S
24
ER
2'5
RR
HELD
_L(?__.R+ER
S PRocEssoR
+
c
FIG.3
32
“m”
31
j
LPF
1
REFLECTION
GENERATOR
I
DELAY
__
:_
i
§1
‘I
—f\ :iFL
"
*FR
J3‘!
LRL
\
L
I
>
L
33
36
____
1
__.J
RR
US. Patent
Aug. 13, 1996
Sheet 4 of 4
5,546,465
FIG. 5
51
S
A
53
--
A
52
S.
Q
A’
A
54
5,546,465
1
2
AUDIO PLAYBACK APPARATUS AND
METHOD
feeling of presence, a sound-?eld signal and a Dolby pro
logic signal are coupled to output audio signals for seven
channels. For the listening environment of an ordinary home
environment, however, it is not easy to install rear speakers,
and moreover, a power ampli?er and speakers for rear
outputs are also required.
BACKGROUND OF THE INVENTION
The present invention relates generally to an audio play
back apparatus and method for an audio system, and more
SUMMARY OF THE INVENTION
particularly, to an audio playback apparatus and method for
outputting sounds containing a sound ?eld in order to better
In order to overcome such problems described above, it is
an object of the present invention to provide an audio
appreciate performances.
A sound ?eld is an indication of audio peculiarities which
are generated in accordance with the environment of a given
location, such as a concert hall, excluding the sounds
actually played therein, such as a performance. A sound ?eld
is made up of a direct wave reaching a listcner’s ear directly
playback apparatus and method in which audio signals for
seven channels made up of a sound~?eld signal and a Dolby
pro-logic signal are converted into signals for fewer chan
15
To accomplish the object of the present invention, there is
from the point of sound origin (e.g., a stage), and a group of
reflection waves re?ected by the walls, ceiling and ?oor (as
provided an audio playback apparatus comprising Dolby
pro-logic decoding means for converting a digital audio
well as other permanently ?xed obstacles) and thereby
signal into a left signal, a right signal, a center signal, and a
surround signal; sound ?eld processing means for convert
ing the left, right, center and surround signals into a front left
signal, a front right signal, a rear left signal, and a rear right
reaching the listener’s car at a time determined according to
the distance from the sound source. Further, the reflection
wave group is divided into two subgroups: one sub-group of
waves which is ?rst reflected by the left and right walls, and
the other which is repeatedly re?ected and re-re?ectcd after
the ?rst re?ection to thereby reach the listener’s car from all
directions and in an irregular pattern.
Along with efforts to reproduce the original sound of a
signal; audio processing means for mixing the left, right,
front left, front right, rear left and rear right signals accord
25
a right-speaker output signal; and audio output means for
outputting the left-speaker output signal via a left speaker,
the right-speaker output signal via a right speaker, and the
been achieved with respect to frequency characteristics or
dynamic range, with the advent of digital audio players such
as a compact disk player or digital audio tape player.
However, an audio playback technique for reproducing the
and particularly, since images are planar, the spatial audio
playback technique is more of a necessity in the reproduc
35
left-speaker output signal and a right-speaker output signal.
BRIEF DESCRIPTION OF THE DRAWINGS
The above object and advantages of the present invention
processor 12, and outputs audio signals L, R, C, FL, FR, RL
An audio signal digitized in an audio signal processor (not
shown) of an audio system is input to Dolby pro-logic
decoder 11. Dolby pro-logic decoder 11 separates and out
puts the input audio signal into four signals: a left signal L,
a right signal R, a center signal C, and a surround signal S.
45
FIG. 1 is a block diagram of a conventional audio
playback apparatus;
50
FIG. 2 is a block diagram of an audio playback apparatus
of the present invention;
FIG. 3 is a block diagram of the sound ?eld processor
shown in FIG. 2;
55
FIG. 4 illustrates a schematic diagram of a circuit that
performs an algorithm for the two—channel sound ?eld
processor shown in FIG. 2; and
FIG. 5 spatially illustrates a transfer function between a
sound source and a listener.
DETAILED DESCRIPTION OF A PREFERRED
EMBODIMENT
Dolby pro-logic decoder 11, and the front left signal FL,
front right signal FR, rear left signal RL and rear right signal
RR which are the output signals of sound ?eld processor 12,
while containing a sound ?eld.
With a conventional audio system in which audio signals
are output through two channels for left and right signals, a
listener cannot feel a “presence” quality of the sound. For a
will become more apparent by describing in detail a pre
ferred embodiment thereof with reference to the attached
drawings in which:
The left signal L, right signal R, center signal C, and
surround signal S are input to sound ?eld processor 12,
which converts and outputs them into four sound ?eld
signals: a front left signal FL, a front right signal FR, a rear
left signal RL, and a rear right signal RR.
In the conventional technology, the audio signal is repro
duced via two channels for left and right signals, or repro
duced via seven channels for the left signal, right signal and
center signal L, R and C which are the output signals of
center signal via a central speaker.
Further, a method is provided which includes the steps of
converting a digital audio signal into a left signal, a right
signal, a center signal, and a surround signal; converting said
left, right, center and surround signals into a front left signal,
a front right signal, a rear left signal, and a rear right signal;
and mixing said left, right, front left, front right, rear left and
rear right signals according to a relationship equation and
converting them into a two channel signal comprised of a
40
tion of sound with a feeling of presence.
In FIG. 1, a conventional audio playback apparatus com
prises a Dolby pro-logic decoder 11 and a sound ?eld
and RR for seven channels.
ing to a relationship equation and converting them into a two
channel signal comprised of a left-speaker output signal and
high-quality sound source, signi?cant improvement has
sound produced in a concert hall or studio like the original
sound in a listening room is unsatisfactory at present, in
view of the space and time dimensions of the original sound.
In a recently developed audio/video system, since a
transmission technique for audio and video signals is unsat
isfactory for transmitting a sufiicient amount of information,
nels, while containing the sound-?eld signal.
Referring to FIG. 2, an audio playback apparatus of the
present invention, comprising a Dolby pro-logic decoder 21,
65
a sound ?eld processor 22, a two-channel sound ?eld
processor 23 and ?rst and second signal mixers 24 and 25,
is designed to convert audio signals for seven channels into
5 ,546,465
3
4
audio signals for three channels, namely, the signals L+EL,
?lters (APF) 35. A signal mixer 36 mixes the re?ection
sound and reverberation, and outputs four sound ?eld sig
nals corresponding to the front left FL, front right FR, rear
left RL and rear right RR signals.
FIG. 4 schematically illustrates an example of a circuit
which performs an algorithm with which two-channel sound
?eld processor 23 of FIG. 2 converts the four sound ?eld
signals into sound ?eld signals for two channels. First front
R+ER and C.
An audio signal digitized by an audio signal processor
(not shown) of an audio system, is input to Dolby pro-logic
decoder 21. Dolby pro-logic decoder 21 separates and
outputs the input audio signal into four signals: a left signal
L, a right signal R, a center signal C, and a surround signal
S.
The left signal L, right signal R, center signal C, and
surround signal S are input to sound ?eld processor 22,
which converts them into four sound ?eld signals: a front left
1O
those of rear sound sources RL and RR. Here, K is an
signal FL, a front right signal FR, a rear left signal RL, and
arbitrary coelIicient determined for sound pressure matching
a rear right signal RR.
Two-channel sound ?eld processor 23 mixes from left
between front sound sources FL and FR and rear sound
sources RL and RR. Filters 43, 44, 45, 46, 47 and 48 convert
input signals according to transfer functions discussed
signal FL, front right signal FR, rear left signal RL, and rear
right signal RR, and converts them into sound ?eld signals
for two channels: left sound ?eld signal EL and right sound
?eld signal ER. A ?rst signal mixer 24 mixes left sound ?eld
signal EL and left signal L of Dolby pro-logic decoder 21,
and generates a signal L+EL output via the left speaker. A
second signal mixer 25 mixes right sound ?eld signal ER
and light signal R of Dolby pro-logic decoder 21, and
generates a signal R+ER output via the right speaker. The
center signal C output from Dolby pro-logic decoder 21 is
output via the central speaker. Therefore, the audio playback
below. Operation devices, such as the adders shown in FIG.
4, mix signals input thereto.
Functions S, A, S‘ and A’ used in the ?lters indicate a
sound source transmission characteristic relationship
between a sound source and a listener's car, as prescribed by
the position of the sound source and the listener‘s sense of
hearing.
25
apparatus ofthe present invention is able to reproduce audio
signals containing a sound ?eld signal employing only three
channels.
Referring to FIG. 3, the sound ?eld processor converts
left, right, center and surround signals L, R. C and S into a
transmission function corresponding to the path between
from sound sources 51 and 52 and the listener’s ear closest
to the respective front sound sources is represented by the
symbol S. An indirect sound transmission function corre
sponding to the path between from sound sources 51 and 52
and the listener’s ear farthest away from the respective rear
beration. A reflection sound portion of the sound ?eld
processor consists of a low-pass ?lter (LPF) 31 for control
walls and the like, and a re?ection generator 32 for gener
ating a reflection sound by using an external memory device
such as a DRAM. A reverberation portion of the sound ?eld
processor comprises a delay circuit 33 for controlling a
predetermined time delay between the reflection sound and
reverberation, four comb ?lters 34 for controlling the mag—
nitude and period of the reverberation, and two all-pass
FIG. 5 is a diagram for illustrating the function of the
sound source transmission characteristic between the vari
ous sound sources and the listener’s car. A direct sound
sound ?eld signal made up of a re?ection sound and rever
ling signal characteristics in accordance with signal fre
quency, depending upon the sound absorption properties of
leveler 41 and second front leveler 42 function to match the
sound pressure levels of front sound sources FL and FR to
sound source is represented by the symbol A. Moreover, a
direct sound transmission function and an indirect sound
35
transmission function for rear right sound source 53 and rear
left sound source 54 are represented by symbols S‘ and A‘,
respectively.
According to the algorithm of FIG. 4, the relationship
40
between the inputs and outputs of the two-channel sound
?eld processor is given according to the following equa
tions, using the reference characters and ?lter functions
indicated in the drawings.
RL] ]
RRl
5,546,465
l
0
FL
ltkliir lll
FR
RL
ll M
RR
S. A
A,S
1,0
0,1
FL
ll lll
FR
25
Therefore, the two-channel sound ?eld processor converts
the front left signal FL, front right signal FR, rear left signal
RL, and rear right signal RR for four channels into left sound
?eld signal EL and right sound ?eld signal ER for two
channels according to the following relationship equation.
EL
A,
ER
S’
l H
RL
ll l+Kl
RR
means for mixing said right sound ?eld signal and said
right signal so as to generate said right-speaker output
signal.
30
3. An audio playback apparatus as claimed in claim 2,
wherein said audio processing means converts said front left
(FL), front right (FR), rear left (RL) and rear right (RR)
signals into said left sound ?eld signal (EL) and right sound
?eld signal (ER) according to the relationship equation as
FL
ll 1
FR
follows:
35
As described above, in the present invention, in order to
reproduce a sound containing a sound ?eld, the conventional
sound signals for seven channels are converted into sound
[ EL
ER
ll 3', A‘ 1 l RL l* K l .9, A l
A‘,
s'
RR
A,
5
FL
FR
signals for three channels so that a listener can feel a rich
where S indicates a direr sound transmission function with
sound presence even when fewer output speakers are 4O respect to a front sound source;
employed than with a conventional audio playback appara
A indicates an indirect sound transmission function with
tus.
respect to said front sound source;
What is claimed is:
S‘ indicates a direct sound transmission function with
1. An audio playback apparatus comprising:
decoding means for converting a digital audio signal into
a left signal, a right signal, a center signal, and a
respect to a rear sound source;
45
surround signal;
K indicates a coefficient for sound pressure matching
sound ?eld processing means for converting said left,
right, center and surround signals into a front left
signal, a front right signal, a rear left signal, and a rear
between said front sound source and said rear sound
source.
50
right signal; and
audio processing means for mixing said left, right, front
left, front right, rear left and rear right signals according
to a relationship equation and converting them into a
two channel signal comprised of a left-speaker output
55
6O
5. An audio playback apparatus as claimed in claim 1,
6. An audio playback method, comprising the steps of:
converting a digital audio signal into a left signal, a right
signal, a center signal, and a surround signal;
converting said left, right, center and surround signals into
a front left signal, a front right signal, a rear left signal,
generate a left sound ?eld signal and a right sound ?eld
signal;
and
left-speaker output signal via a left speaker, said right
speaker output signal via a right speaker, and said center
signal via a central speaker.
means.
function between a sound source and a listener so as to
means for mixing said left sound ?eld signal and said left
signal so as to generate said left-speaker output signal;
4. An audio playback apparatus as claimed in claim 1,
further comprising an audio output means for outputting said
wherein said decoding means is a Dolby pro-logic decoding
signal and a right-speaker output signal.
2. An audio playback apparatus as claimed in claim 1,
wherein said audio processing means comprises:
means for converting said front left, front right, rear left
and rear right signals according to a transmission
A‘ indicates an indirect sound transmission function with
respect to said rear sound sources; and
and a rear right signal; and
65
mixing said left, right, front left, front right, rear left and
rear right signals according to a relationship equation
and converting them into a two channel signal com
5,546,465
7
8
prised of a left-speaker output signal and a right
lZZlZZlfI-Z illiilt‘lil illiiil
speaker output signal.
7. An audio playback method as claimed in claim 6.
wherein said mixing step comprises the steps of:
converting said front left. front right, rear left and rear
right signals according to a transmission function
between a sound source and a listener so as to generate
a left sound ?eld signal and a right sound ?eld signal;
mixing said left sound ?eld signal and said left signal so
as to generate said left-speaker output signal; and
5
where S indicates a direct sound transmission function with
respect to a front sound source;
A indicates an indirect sound transmission function with
respect to the from sound source;
8‘ indicates a direct sound transmission function with
respect to a rear sound source;
A‘ indicates an indirect sound transmission function with
respect to the rear sound source; and
mixing said right sound ?eld signal and said right signal
K indicates a coefficient for sound pressure matching
so as to generate said right-speaker output signal.
8. An audio playback apparatus as claimed in claim 7,
wherein said step of converting said front left (FL), front
right (FR), rear left (RL) and rear right (RR) signals into said
between said front sound source and said rear sound
left sound ?eld signal (EL) and right sound ?eld signal (ER),
outputs the left and right sound ?eld signals according to the
relationship equation as follows:
source.
9. An audio playback method claimed in claim 6, further
comprising a step for outputting said left-speaker output
signal via a left speaker, said right-speaker output signal via
a right speaker, and said center signal via a central speaker.
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