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Name of the Patent Office President October 10, Showa 4e Title of invention of invention 4
channel stereo sound reproduction system% formula% (K or J name) whereabouts Tokyo, Tokyo
Chiyoda Ward Marunouchi-Shimoguchi 5 No. 1 ■ JP Sho-48-439 C) L examination request (all 7
pages) Office internal reference number 10 Japan classification 171723 (/ l) 2 IV description
title of the invention 4-channel stereo recording playback system title of the invention 4-channel
stereo recording playback system
■ Japan Patent Office
DETAILED DESCRIPTION OF THE INVENTION The present invention is a so-called 4-2-4 multistereo system% system in which 4-channel signals can be recorded and reproduced using
conventional stereo disk records and magnetic tapes. Recording and reproduction in the -4 multi
stereo system are performed as follows. FIG. 1 is a block diagram showing a conventional system,
in which 1 is a recording room. In the recording room 1, four microphones 1a. Four signals E1.
E、。 E3. The signal E4 is converted by the mixing circuit 2 into a signal of 2 channels. In
this case, generally, four or more and sixteen or so microphones are used, but these signals are
appropriately mixed to form four channel signals (which are two channel signals as described
above). 3 is a normal recording disk recording device such as a recording or reproducing device
such as a magnetic tape. When the above 2 channel signals are to be recorded by the normal
stereo recording and playback by the playback device 3 i, the normal stereo recording and
playback device 3 is first played back as a 2 channel signal from the playback device 3
Decomposition Matrix EndPage: Decomposition by 4 signals "" "E21 E (, g7) by 4 boxes. The four
speakers 5a, 5b, 5c, 5d are driven by these four signals. In this way, a 4-channel stereo is
reproduced in the listening room 5. This reproduced four signals E, ', E (, Et. Ej is the original
signal E1. E2. E3. It does not correspond completely one to one with E, and contains an
extra signal that crosses each other between signals. For this reason, the sense of sound in the
listening room 5 is different from the sense of sound in the recording room 1, and causes
blurring of the sound image, and rotation of sound image localization due to the listening
position. In the past, various proposals have been made to improve such crosstalk between the 42-4 system and the four channels, but none of them are insufficient, or their logic operations are
erroneous. In some cases, even if the sound quality is adversely affected. Among them, the
method 1 of controlling the reproduction level between channels also by comparison of the
reproduction level, for example, the Scheiver system (5 cheiber system), the CBS SQ system.
However, since these operations are performed only on the playback side, they are often very
different from the correct level instruction. (1) The object of the present invention is to provide a
four-channel, Korean-speaking Korean sound reproduction system which reproduces the
reproduction level of a valley channel accurately and obtains excellent crosstalk characteristics,
except for the above-mentioned drawbacks.
In order to achieve the above object, the present invention converts signals of four channels into
two channels on the recording side and extracts in advance characteristic signals that indicate
relationships between sound sources such as intensity ratios among the channels. Note that this
is recorded along with the baseband signal in the unused band on the high band side of the
baseband signal, and the playback side is used to control the playback level of each channel (by
controlling the playback level for each channel). Is an accurate reproduction with less crosstalk.
FIG. 2 shows the distribution of signals in the case of converting 4 channels of information
according to the method of the present invention into 2 channels and recording on a disk record,
magnetic tape or the like. For example, in the left channel L, the four signals are mixed in the
base band and J 十 E3-mg, (m is a mix factor / 7 g coefficient and m <1) is in the base band of the
right channel. Record E2 + E4171B3. For a stereo recording or magnetic tape to be used here, a
general six device having a bandwidth of about 20 KHz is sufficient. In the band of 20 KHz or
more, the recording level, playback and bell etc. decrease, but when the occupied band is narrow
like the feature signal and a large SZN ratio (signal S to noise N ratio) is not required, There is
enough recording capacity for In this unused band, L side <y ratio g1 / E3. On the R side, the
ratio E2 / E4 is converted to a band of 20 to 25 KHz as shown in FIGS. 2 (a) and 2 (b) using an
operation such as frequency modulation, and is recorded simultaneously with the baseband
signal. . In this case, since the level of the music signal of each channel changes relatively slowly,
the required band of the characteristic signal such as the intensity ratio is only about several
hundreds Hz. For this reason, even if it converts to an FM (frequency modulation) signal, a
necessary band is 2 to 3 KHz. For recording the feature signal to the above unused information v
outside the basic band, the influence of uneven rotation, level fluctuation, etc. is appropriate for
the bell FPi, but in some cases the required band is narrow It can be referred to as Z using
amplitude modulation. The present invention will be described in detail by the following
examples. 3 and 4 show the C embodiment of the present invention. FIG. 3 is a block diagram of
a circuit for performing the operation on the recording side and FIG. 4 for performing the
operation on the reproduction side. In FIG. 3, 6 is a mixing matrix circuit, 71.72 is two
designated; level comparison circuit comparing levels between channels, 81 ° 82 is a low pass
filter, 9 is a carrier generator, 101 ° 102. Is an FM modulator, and 111 and 112 are mixed
Four signals E1. And E4 collected into four channels collected in the recording room. E2.
E3. E4 is converted to a 2-channel signal through the mixing matrix circuit 6. As the matrix
circuit 6Q matrix, for example, the following matrix of End Row 2 of 4 in 2 rows and 4 columns is
used. 01 ml where m: mixing constant m <1 Furthermore, as a matrix other than the above
equation, m) -n1 where m, n: using mixing constant and using m, n as a constant, complex
number, or arithmetic element It can also be done. On the other hand, the level ratio of E and E3
is detected at 71, and the level ratio of E2 and E4 is detected at 72. These outputs are added to
the low pass filters 81 and 82 to form narrow band signals. The cut-off frequency of the low pass
filter is about 200 Hz. Although the bandwidth of the signal handled by this level comparison
circuit reaches about 20 KH'z, it is mainly a music signal, so its level change is relatively gentle,
even if the bandwidth is limited to about 200 Hz, It can sufficiently cope with the change of the
music signal. This signal is a feature signal indicating the relationship of strength between the
four music signals "'1'pE2 + B3'1b4" and is used to determine which channel's signal is dominant
on the playback side. This narrowband feature signal frequency modulates the carrier wave from
carrier generator 9 by Frl modulator 101 ° 102. This frequency modulation, for example, has a
spectrum between 20 KH'z and 25 KHz and, together with the output power of the mixing matrix
circuit 6, makes the mixing circuits 111 and 112 through two channels of confidence. The
frequency distribution of this synthesized 2-channel signal is as shown in FIG. 2 (a,) and (b)
shown above. This signal is recorded on a conventional 2-channel disc record or magnetic tape
or the like. In the case of this recording, if the band of the recording device is narrow enough to
significantly attenuate the portion of the characteristic signal, decelerated recording may be
performed. In the above description, the bandwidth of the feature signal after modulation is 5
KHz. However, since it is sufficient if the S / N ratio is 20 dB, even if narrowing from 500 Hz to 'l
KHz, it can withstand practical use sufficiently. Further, since this characteristic signal is
recorded in a frequency band of 20 KHz or higher, reproduction of a disk record and a magnetic
tape recorded by the method of the present invention with a normal stereo reproduction
apparatus is not recommended at all. Next, the reproduction side will be described. FIG. 4 is a
block diagram of an apparatus Ω for reproducing the sound i according to the above method.
12 is a disk record, 2 channel resuming device for extracting 2 channels of electric signal from
magnetic tape, 131, 132 is a filter for separating a baseband signal and a μ to quadrature signal,
14 is a level comparison circuit 151. 152 Demodulation circuit 16 is a control circuit for
controlling four signals and bells based on signals from level comparison circuit 14 and
demodulation circuits 151 and 152, and 17 is a decomposition matrix circuit 181 ° 1 '82, 183,
184. Is a decompression compression circuit. The operation of this reproduction system will be
described below. First, the signal of the 2-channel disc recorded from the disc 2 or the magnetic
tape recorded by the method described above with the 2-channel bio-generator 12 is reproduced.
This 9 signal. Rとする。 This signal consists of one channel, the baseband signal, and a highfrequency feature signal above. This composite signal is applied to the filter 131 ° 132 and
separated into a baseband signal and a feature signal, respectively. The two separated baseband
signals L /, R / are applied to the decomposition matrix circuit 17. This decomposition matrix
circuit is a 4 × 2 matrix symmetrical to the mixing matrix circuit 6. The following is obtained by
multiplying the mixing matrix of the first equation and the decomposition matrix of the third
equation. EndPage: 3 Furthermore, if normalization is performed as in the following equation, the
outputs between the respective main channels become identical. Here, K = V /, and 'm2. The
matrix of 4 rows and 4 columns in the above equation is E, m2 ° E3. E、とJgJ、E7. It
shows the relationship between E and E, and indicates the amount of crosstalk between each
channel that occurs when a 4-channel signal passes through a 2-channel transmission system. 〜
−3,dBである。 This crosstalk can be improved by the circuit shown in FIG. The operation
will be described below. The signals separated by the filters 131 and 132 are demodulated by
the demodulation circuits 351 and 152 and separated by the radio units 131 and 13 by 6 ° as
the original low frequency, narrow band feature signals. A part of the two baseband signals L /, R
/ is subjected to level comparison between the two channels through the level comparison circuit
14. The three output signals of the level comparison circuit 14 and the demodulation circuits
151 and 152 have three independent level ratios for the sweep signal indicating the level
relationship between the original four channel signals. By using this, it is possible to accurately
convey information such as which channel of the four channels is large.
The above three feature signals are applied to the control circuit 16 to determine which channel
signal is large, and the four channel expansion and compression circuits 181 and 182 ° 183.
184 are individually controlled. By this circuit operation, the original input signal E1 ° E2.
E3. Any one of E, or any combination thereof can be designated -7,1. This can improve
crosstalk by 10 to 15 dB. The expansion and compression circuits 181 to 184 may be known
circuits, for example, a circuit that increases the amplification by 10 dB at a positive control
voltage and decreases OaB at a negative voltage. The logic determination operation in the control
circuit 16 is as follows. Do what you do. When there are four independent signals, there are 15
possible combinations of the signals (or signals to be considered as signals to be emphasized)
existing among them, as shown in the right side of FIG. Become. Since the determination
operation is easily understood digitally, it will be explained by digital determination logic. Now,
three ratios of the ratio L // R, / of the baseband signals L / and R / of the outputs of t / E 3, E
2 / E 4 r and the filters 131, 132 are obtained as characteristic signals. ここで、
s>1のとき+−1E、=E 3のときO。 A digital signal is generated by providing
a-+ value so that E, / E3 <z, and a -1 threshold. Similarly, m2 / B + to +1; 0. A signal of -1 is
obtained from L // R 'to a signal of + ItOp "1. Since there are 27 combinations of these
combinations, it is possible to completely specify all 15 channels required to enhance the signals
of the above four channels. ,. The ratio L // R / of these baseband signals and EndPage: 4
produced from the original signals E, / E3. When B2 / E is digitally displayed, it is as shown on
the fifth left side. In the figure, + represents +1, 0 represents O, and-represents -1. The black
circles shown on the right side of the figure indicate that there was a signal in the channel. When
the signal shown on the left side of FIG. 5 is received, a positive control signal is added to the
channel indicated by a black circle on the right side, and a negative control signal is added to the
other channels. In this way, the signal of the designated channel can be expanded and
compressed. As described above, the simple non-logic operation allows the locations of the
outputs of the four independent channels to be clearly transmitted to the playback side, and the
output of the channel corresponding to the original input is expanded, The output of the channel
corresponding to the channel having no input (crosstalk causes a signal to appear at the output)
can be compressed to improve crosstalk.
In the above description, simple table information such as level comparison of input valley
channel is transmitted as a characteristic signal outside the basic band, and on the reproduction
side, using this, it is described using a simple 3fi logic as a logic operation. However, it is also
possible to use the amount of level ratio as it is for Yj, as it is-(· Ki, and an example using a simple
level ratio as the feature signal has been described, but in addition to the level ratio, The
information on whether or not the output exists in the specified band, the level ratio existing in
the low band part and the high band part of the two designated channels, etc. are also converted
into strong information, and this is frequency shifted It can be modulated and transmitted as a
hunting signal. In this case, the bandwidth required for transmission of the 4n ′ ′ signal (信号
± IKHz and so on. It may be narrow. As described above, according to the present invention, it is
possible to conveniently count the apparatus having a simple circuit configuration, which is a
drawback of the conventional 4-2-4 recording and reproduction system. In addition, the present
invention can provide high quality 4-channel stereo recording and reproduction without
requiring major changes in conventional recording media, pickup cartridges, magnetic heads and
the like. Furthermore, the disk record magnetic tape manufactured according to the method of
the present invention does not give a t-to-fold signal interference even when it is reproduced by a
normal 2-channel stereo reproduction apparatus. Also, even if it is played back by the
conventional 4-2-4 type playback device, it can be played back as a normal matrix 4-channel
stereo. There is also compatibility with conventional ones. Figure 2 (a), (b) is a schematic diagram
in the case of transmission by the equation, Figure 2: (a), (b) shows the spectrum arrangement on
the recording medium of the detection signal or the baseband signal according to the present
invention; FIG. 4 is a block diagram showing an embodiment of the present invention, and FIG. 5
is a view showing the relationship between a feature signal and a signal for controlling expansion
and compression of each channel as a crosstalk improvement signal. 6 is a mixing matrix circuit,
71.72 is a level comparison circuit) 81.82 is a low-pass filter, 9 is a carrier generator 101.102 is
an FM modulator 1.111, 112 is a mixing circuit, 12 is a 2 channel Regenerator, 1ul 1132 is a
filter, 14 is a level comparison circuit, IIM. 152 is a demodulator, 16 is a control circuit% 17,
resolution matrix times%, and 181 to 184 are expansion and compression circuits. Attorney
Attorney Attorney Mr. Yumada End Page: 5 1st Order '$ 2 Figure R Number zog H, 25 kl -1 °
Figure 5 End Page: 6 List of Appended Documents (1) One Specification (2) One Drawing (1) 3)
Delegation 吠 1 (4) Patent Application Subsidiary 1-Other Inventors, Patent Applicants or Agent
Inventors EndPage: