Sound reproducer for high definition television

A sound reproducer is disclosed for a Hi-vision 3-1 sound system composed of an audio signal decoding unit coupled with an AV amplifier, which amplifier has a surround processor and is originally arranged for reproducing surrounding sounds from two-channel stereophonic audio signals of the Dolby.RTM. surround system, wherein volume controllers for controlling right and left rear Hi-vision audio signals of monaural and a center front Hi-vision audio signal, and first through third switching circuits for selecting outputs of the audio signal decoding units, are provided in case of reproducing sounds of the Hi-vision 3-1 sound system, or outputs of the surround processor, in case of reproducing sounds of the two-channel sound surround system, for providing the acoustic balance of the audio signals when the first through third switching circuits are switched to reproduce the sounds of the Hi-vision 3-1 sound system.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a sound reproducer for a high definition 
television (hereinafter referred to as "Hi-vision") system and, more 
particularly, to a sound reproducer of the type for reproducing 
surrounding sounds in accordance with a Hi-vision sound system by making 
use of an Audio-Video (AV) amplifier originally arranged for the Dolby 
(registered trademark) surround system which is one of two-channel sound 
surround systems. 
i. Description of the Prior Art 
The Hi-vision system is a television system proposed for the next 
generation of television systems and is capable of reproducing powerful, 
fine-grained, rich with colors and high-definition images in a large-sized 
display as compared with the existing television systems. Accordingly, it 
is required to provide a sound reproducer of the Hi-vision system with a 
sense of presence and high quality fit for the high quality Hi-vision 
images. 
To study a sound reproducing system suitable for the Hi-vision images, 
experiments for evaluating a number of stereophonic sound reproducing 
systems have been implemented in order to determine the optimum number 
audio channels to be employed and an arrangement of speakers. Through 
these experiments, it was found that a 3-1 sound reproducing system is the 
most suitable in all respects, for reproducing a surrounding sound effect 
for the Hi-vision images. The 3-1 sound reproducing system has an optimum 
number of three audio channels and an optimum arrangement of speakers such 
that three front speakers for the three audio channels and two rear 
speakers for a monaural audio channel. In the arrangement of the front and 
rear speakers, two speakers are arranged at the right (R) front and left 
(L) front of the listener and that one speaker at the center (C) front, 
while two speakers are arranged at the right (R) rear and left (L) rear of 
the listener. 
The Hi-vision 3-1 sound system is a kind of four-channel stereophonic sound 
reproducing system consisting of three front audio channels and one rear 
audio channel and is capable of realizing a so-called surrounding sound 
effect fit for Hi-vision images as if the listener were in the midst of 
the reproduced sounds. 
In order to reproduce audio signals in accordance with the Hi-vision 3-1 
sound system by employing a two-channel stereophonic amplifier, it is 
necessary to adapt at least three amplifiers in total, one amplifier for 
the right and left front audio signals, one amplifier for the center front 
audio signal and one amplifier for the right and left rear audio signals, 
thus resulting in a large-scaled sound reproducing system. 
As an alternative to the above, it may be thought of by those skilled in 
the art to adapt an AV (audio and video) amplifier employed in the Dolby 
surround system, wherein three front audio channels of L, R and C and one 
rear audio channel reproduced are for making four audio channels in total. 
However, as shown in FIG. 2, the AV amplifier for use in the Dolby 
surround system converts two-channel stereophonic sound signals of SL and 
SR, which are fed to input terminals of 1a and 1b, into four-channel, five 
signals by means of a contained surround processor 2, wherein the five 
signals are Right and Left front signals of FR and FL, Right and Left rear 
signals of RR and RL, whereas RR and RL are the same signal, and a Center 
front signal of FC. 
In the circuit configuration as described above, the signals FL and FR are 
fed directly to main volume controllers 3a and 3b, while the signals RL, 
RR and FC are fed to main volume controllers 3c, 3d and 3e through 
balancing volume controllers 4a, 4b and 4c, whereby the sound volume as 
well as the acoustic balance of reproduced sounds are controlled 
respectively. The main volume controllers 3a-3e are interlocked each other 
in the operation. 
Each audio signal controlled by the main volume controllers 3a-3e is output 
to each exterior speaker (not shown) from respective output terminals 
7a-7e through connecting terminals 5a-5e and power amplifiers 6a-6e. This 
circuit configuration, however may cause a problem for the AV amplifier, 
in case of amplifying the audio signals in accordance with the Hi-vision 
3-1 sound system, such that it is possible to apply the front audio 
signals of two channels R and L, but unable to apply the rear audio signal 
of one channel S and that the front center audio signal of one channel C 
thereunto. 
To eliminate the above problem, connecting pins are pulled off from the 
connecting terminals, and the rear audio signal and the front center audio 
signal may be fed directly to the power amplifiers 6c-6e through the 
connecting terminals 5c-5e by applying the rear audio signal 
simultaneously on the audio channels R and L provided for amplifying the 
audio signals RR and RL and providing the front center audio signal on the 
audio channel C provided for amplifying the audio signal FC. 
However, even with the modification, since the rear audio signal and the 
front center audio signal are fed directly to the power amplifiers 6c-6e 
as the audio signals of RR, RL and FC without passing through the volume 
controllers, another problem is caused such that there is no way to 
control the acoustic balance between the audio signals. 
SUMMARY OF THE INVENTION 
It is therefore an object of this invention to provide a Hi-vision sound 
reproducer capable of controlling acoustic balance between audio signals 
in the event of reproducing audio signals in accordance with the Hi-vision 
3-1 sound system by employing an AV amplifier developed for the Dolby 
surround system. 
A sound reproducer in accordance with this invention comprises a surround 
processor for converting stereophonic right and left audio signals in two 
channels into right, left and center front audio signals in three channels 
and right and left rear audio signals in two channels, first and second 
power amplifiers for amplifying the right and left front audio signals in 
two channels and driving two corresponding right and left front speakers, 
first through third sound volume controllers for controlling center front 
audio signal in one channel and right and left rear audio signals in two 
channels, fourth through sixth sound volume controllers (fifth and sixth 
sound volume controllers are not shown separately in the drawing) for 
controlling the center front Hi-vision audio signal in one channel and 
right and left rear Hi-vision audio signals of monaural in two channels, 
first through third switching circuits for switching outputs between the 
first through third sound volume controllers and the fourth through sixth 
sound volume controllers, and third through fifth power amplifiers for 
amplifying the center front audio signal in one channel and the right and 
left rear audio signals in two channels fed from the first through third 
switching circuits and driving a center front speaker and right and left 
rear speakers, whereby, in case of reproducing audio signals of the 
Hi-vision 3-1 sound system, outputs of the fourth through sixth sound 
volume controllers are selected by the first through third switching 
circuits while, in case of reproducing audio signals of the two-channel 
sound surround system, outputs of the first through third sound volume 
controllers are selected by the first through third switching circuits. 
As it has been described above, in case of reproducing the audio signals of 
the Hi-vision 3-1 sound system, since the outputs of the fourth through 
sixth sound volume controllers are selected by the first through third 
switching circuits, the right and left front Hi-vision audio signals in 
two channels are fed directly to the first and second power amplifiers 
through the surround processor for amplification, the center front 
Hi-vision audio signal in one channel is fed to the third power amplifier 
through the fourth sound volume controller for amplification, and the 
right and left rear Hi-vision audio signals in two channels are fed to the 
fourth and fifth power amplifiers through the fifth and sixth sound volume 
controllers for amplification, and then all the amplified audio signals 
are fed to respective speakers for reproducing the surrounding sounds for 
the Hi-vision system. Accordingly, the acoustic balance of the audio 
signals can be adjusted effectively by utilizing the fourth through sixth 
sound volume controllers. 
On the other hand, in case of reproducing the audio signals of the 
two-channel sound surround system, the outputs of the first through third 
sound volume controllers are selected by the first through third switching 
circuits. In this case, the two-channel audio signals are fed to the AV 
amplifier, and provided are the right and left front audio signals in two 
channels, the center front audio signal in one channel by adding the 
two-channel audio signals being fed, and the right and left rear audio 
signals for monaural in two channels by subtracting the two-channel audio 
right and left front. 
In this way, the derived right and left front audio signals in two channels 
are fed to the first and second power amplifiers for amplification, the 
derived center front audio signal in one channel is fed to the third power 
amplifier through the first volume controller and that the right and left 
rear audio signals in two channels are fed the the fourth and fifth power 
amplifiers through the second and third volume controllers for 
amplification. The amplified audio signals are then applied on respective 
speakers arranged in front and rear of the user. 
In accordance with this invention, it is possible to reproduce audio 
signals of the Hi-vision 3-1 sound system by making use of an AV 
amplifier, which contains a surround processor and is developed for the 
two-channel sound surround system, for providing the acoustic balance of 
the audio signals.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
The preferred embodiment of this invention will now be described in detail 
by referring to the accompanying drawings. Referring to FIG. 3, there is 
shown a sound reproducer for reproducing sound signals in accordance with 
the Hi-vision 3-1sound system. 
The sound reproducer in accordance with this invention consists of a 
Hi-vision audio signal decoding unit 10 and an AV amplifier 20 arranged 
for the Dolby surround system. The audio signal decording unit 10 includes 
a circuit for providing the AV amplifier 20 with five signals of right 
front audio signal FR, left front audio signal FL, center front audio 
signal FC, right rear audio signal RR and left rear audio signal RL by 
converting the four-channel audio signal of SR (right), SL (left), SS 
(surround) and FC (center) of the Hi-vision 3-1 sound system thereinto 
when the sound reproducer is switched to a Hi-vision mode, and by 
converting the two-channel stereophonic sound signals of SR (right) and SL 
(left) of the Dolby surround system thereinto when the sound reproducer is 
switched to a Dolby surround mode. 
In operation of the audio signal decoding unit 10, the audio signals SL and 
SR fed to input terminals 11a and 11b of the audio signal decoding unit 10 
will be derived therefrom as they are. The audio signal SS fed to an input 
terminal 11c has its valve controlled by means of a volume controller 14a 
after being amplfied by an amplifier 13a, once again amplified by an 
amplfier 15a, and then fed to one of fixed terminals of both switching 
circuits 16a and 16b by separating it into two-channel signals. In like 
manner, the audio signal SC fed to an input terminal 11d has it valve 
controlled by means of a volume controller 14b after being amplfied by an 
amplifier 13b, again amplified by an amplifier 15b, and then fed to one of 
fixed terminals of a switching circuit 16c. 
The other fixed terminals of the switching circuit 16a-16c are connected 
respectively to input terminals 17a-17c for receiving audio signals frodm 
the AV amplifier 20 hereinafter described in detail. Movable terminals of 
the switching circuits 16a-16c are connected to output temrinals 18a-18c 
of the audio signal decoding unit 10, whereby the audio signal applied on 
the input terminal 17a or the audio signal amplfied by the amplifier 15a 
is output from the output terminal 18a as the audio signal RL, the audio 
signal applied on the input terminal 17b or the audio signal amplified by 
the amplifier 15a is output from the output terminal 18b as the audio 
signal RR, and all that the audio signal applied on the input terminal 17c 
or the audio signal amplified by the amplifier 15b is output from the 
output terminal 18c as the audio signal FC. The selected audio signals FL, 
FR, RL, RR and FC are in turn fed to the AV amplifier 20 respectively. 
Further, the switching circuits 16a-16c are interlocked in operation for 
switching. 
The AV amplifier 20 arranged for the Dolby surround system includes a 
surround processor 23 which derives five signals of right and left front 
output signals FR, and FL, right and left rear output signals RR and RL of 
monaural and a center front output signal FC by converting, with a help of 
an inner contained logic circuit, the reproduced right and left 
stereophonic audio signals SR and SL fed from input terminals 21a and 21b 
through interlocked switching circuits 22a and 22b. The audio signals FL 
and FR amongst the output signals of the surround processor 23 are fed 
directly to main volume controllers 24a and 24b which are provided for 
controlling sound volume while the remaining three audio signals of RR, RL 
and FC are fed to main volume controllers 24c-24e through volume 
controllers 25a-25c which are provided for controlling acoustic balance. 
The main volume controllers 24a throught 24e are structurally interlocked. 
Moreover, it is so arranged in the circuit that the reproduced 
stereophonic signals SL and SR applied on the input terminals 11a and 11b 
of the audio signal decoding unit 10 are fed directly to the main volume 
controllers 24a and 24b at the time when the switching circuits 22a and 
22b are turned off. 
Outputs of the main volume controllers 24a and 24b are fed to output 
terminals 26a and 26b and then to input terminals 28a and 28b by means of 
connecting pins 27a and 27b. Further, outputs of main volume controllers 
24c-24e are fed to input terminals 17a-17c of the audio signal decoding 
unit 10 through output terminals 26c-26e of the AV amplifier 20. Still 
further, input terminals 28c-28e of the AV amplifier 20 are connected to 
output terminals 18c-18c of the audio signal decoding unit 10. The audio 
signals received at the input terminals 28a-28e are then amplified by 
power amplifiers 29a-29e and fed to respective speakers from output 
terminals 30a-30e. 
In accordance with the circuit configuration as described above, to 
reproduce audio signal of the Hi-vision 3-1 sound system, the movable 
terminals of the switching circuits 16a-16c the audio signal decoding unit 
10 are switched to the fixed terminals connected to the amplifiers 15a and 
15b and, at the same time, the switching circuits 22a and 22b of the AV 
amplifier are turned off for setting the sound reproducer to the Hi-vision 
mode. 
In the Hi-vision mode, the audio siganls SL and SR supplied to the input 
terminals 11a and 11b of the audio signal decoding unit 10 are fed 
directly to the input terminals 21a and 21b through the output terminals 
12a and 12b of the audio signal decoding unit 10. The audio signal SS 
applied to the input terminal 11c of the audio signal decoding unit 10 has 
its valve controlled by the volume controller 14a for providing the 
acoustic balance, and fed in turn to the input terminals 28c and 28d of 
the AV amplifier 20 as the separated audio signals of RL and RR through 
the switching circuits 16a and 16b. Similarly, the audio signal SC applied 
to the input terminal 11d of the audio signal decoding unit 10 has its 
valve controlled by the volume controller 14b for providing the acoustic 
balance, and fed in turn to the input terminal 28e of the AV amplifier 20 
as the audio signal FC through the switching circuit 16c. 
In the AV amplifier 20, the audio signals SL and SR received at the input 
terminals 21a and 21b are fed directly to the main volume controllers 24a 
and 24b for controlling their values after by-passing the surround 
processor 23. The volume-controlled audio signal SL is then fed, through 
the output terminal 26a, connecting pin 27a and input terminal 28a, to and 
amplified at the power amplifier 29a, and supplied to the left front 
speaker as an audio signal FL from the output terminal 30a. On the other 
hand, the volume-controlled audio signal SR is also fed, through the 
output terminal 26b, connecting pin 27b and input terminal 28b, to and 
amplified at the power amplifier 29b, and supplied to the right front 
speaker as an audio signal FR from the output terminal 30b. The audio 
signals RL, RR and FC received at the input terminals 28c, 28d and 28e are 
directly amplified by the power amplifiers 29c, 29d and 29e, and supplied 
respectively to the right and left rear speakers and to the center front 
speaker. 
Consequently, in case of operating under the Hi-vision mode, the sound 
volume of the audio signal FL and that of the audio signal FR are 
controlled by means of the volume controllers 24a and 24b, the sound 
volume of the audio signals RL and RR (i.e. audio signal SS) is controlled 
by the volume controller 14a and the volume of the audio signal FC is 
controlled by the volume controller 14b, thus provided is the acoustic 
balancing between the audio signals in the four channels. 
On the contrary, in case of reproducing sounds in accordance with the Dolby 
surround system, the movable terminals of the switching circuits 16a-l6c 
of the audio signal decoding unit 10 are switched to a side of input 
terminals 17a-17c and, at the same time, the switching circuits 22a and 
22b of the AV amplifier 20 are turned on for operating under the Dolby 
surround mode. 
When the sound reproducer is operating under the Dolby surround mode, the 
reproduced two-channel sterophonic audio signals SL and SR supplied to the 
input terminals 11a and 11b of the audio signal decoding unit 10 are 
output, in the same way as that of the Hi-vision mode, from the output 
teminals 12a and 12b, and then fed to the input terminals 21a and 21b of 
the AV amplifier 20. 
In the AV amplifier 20, the audio signals SL and SR received at the input 
terminals 21a and 21b are processed in the surround processor 23 in 
accordance with a required logic operation, and then output four-channel 
five signals therefrom. That is, the input signals SL and SR are passed 
through the surround processor for outputting the unprocessed input 
signals SL and SR as the right and left front signals Fl and FR, while the 
input signals SL and SR are subtracted in the surround processor for 
outputting a subtracted signal (SL-SR) as the right and left rear monaural 
signals RL and RR, and the input signals SL and SR are added in the 
surround processor for outputting an added signal (SL+SR) as the center 
front signal FC. 
In the audio signals derived from the surround processor 23, the audio 
signals FL and FR are fed directly to the main volume controllers 24a and 
24b for controlling the sound volume thereof, whereby the 
volume-controlled audio signals FL is fed to the power amplifier 29a 
through the output terminal 26a, connecting pin 27a and input terminal 
28a, and then the amplified audio signal FL is fed to the left front 
speaker through the output terminal 30a, while the volume-controlled audio 
signal FR is fed to the power amplifier 29b through the output terminal 
26b, connecting pin 27b and input terminal 28b, and then the amplified 
audio signal FR is fed to the right front speaker through the output 
terminal 30b. 
Further, the audio signals RL, RR and FC are fed to the volume controllers 
25a-25c, and then to the main volume controllers 24c-24e for controlling 
both the acoustic balance and sound volume. The volume controlled audio 
signals RL, RR and FC are in turn fed to the input terminals 17a-17c of 
the audio signal decoding unit 10 through the output terminals 26c-26e. 
In the audio signal decoding unit 10, since the movable terminals of the 
switching circuits 16a-16c are switched to the fixed terminals connected 
to the input terminals 17a-17c, the input audio signals RL, RR and FC 
received at the input terminals 17a-17c are fed to the output terminals 
18a-18c through the switching circuits 16a-16c, and then to the input 
terminals 28c-28e of the AV amplifier 20. The audio signals received at 
the input terminals 28c-28e are fed to the power amplifiers 29c-29e and 
the amplified audio signals are applied respectively on the right rear 
speaker, left rear speaker and center front speaker through the output 
terminals 30c-30e. 
As it has been described herein above, according to the present invention, 
the four-channel audio signals in accordance with the Hi-vision 3-1 sound 
system can be reproduced properly by providing the adjustment of the 
acoustic balance therebetween with use of the AV amplifier arranged for 
the Dolby surround system. 
It is to be understood by those skilled in the art that the foregoing 
description relates only to the preferred embodiment of the invention and 
that various changes and modifications may be made in the invention 
without departing from the spirit and scope thereof.