US3872249A - Encoding method for converting multi-channel sound signals into 2-channel composite signals - Google Patents

Encoding method for converting multi-channel sound signals into 2-channel composite signals Download PDF

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Publication number
US3872249A
US3872249A US427932A US42793273A US3872249A US 3872249 A US3872249 A US 3872249A US 427932 A US427932 A US 427932A US 42793273 A US42793273 A US 42793273A US 3872249 A US3872249 A US 3872249A
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channel
signal
phase shift
sound input
amplitude level
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US427932A
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Susumu Takahashi
Ryosuke Ito
Koichi Hirano
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Sansui Electric Co Ltd
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Sansui Electric Co Ltd
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04H—BROADCAST COMMUNICATION
    • H04H20/00—Arrangements for broadcast or for distribution combined with broadcast
    • H04H20/86—Arrangements characterised by the broadcast information itself
    • H04H20/88—Stereophonic broadcast systems
    • H04H20/89—Stereophonic broadcast systems using three or more audio channels, e.g. triphonic or quadraphonic
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04S—STEREOPHONIC SYSTEMS 
    • H04S3/00—Systems employing more than two channels, e.g. quadraphonic
    • H04S3/02—Systems employing more than two channels, e.g. quadraphonic of the matrix type, i.e. in which input signals are combined algebraically, e.g. after having been phase shifted with respect to each other

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  • ABSTRACT An encoding method for use in a four-channel matrix system in which a front sound signal in one channel signal consists of a relatively large amplitude portion and a relatively small amplitude portion in phase quadrature with each other and the front sound signal in another channel signal is substantially in phase with the front sound signal in the one channel signal and consists of relatively small amplitude portions in phase quadrature with each other, and a back sound signal in one channel signal consists of a relatively large amplitude portion and a relatively small amplitude portion in phase quadrature with each other and the back sound signal in another channel signal is substantially in opposite phase with the back sound signal in the one channel signal and consists of relatively small amplitude portions in phase quadrature with each other.
  • the present encoding method can improve the separation characteristic between the two composite signals and reduce the
  • A denotes a blend quantity whose representative value is 0.414 sin 22.5/cos 22.5").
  • the front-left signal I left signal L and back-left signal L included in the right channel signal R are greater in amplitude level than the front-right signal R and back-right signal R included in the left channel signal L
  • the front signals L, and R included in the right and left channel signals L and R respectively, are phase shifted by a reference angle
  • the back signals L and R included in the left channel signal L are phaseshifted by an angle equal to a reference angle plus 90 while the back signals R and L included in the right channel signal R are phase shifted by an angle equal to a reference angle minus 90.
  • the encoding system as shown in the above expression (1) has the following advantages. Since the front signals are coupled with the same phase to the first and second channels and the back signals are coupled with an opposite phase to the first and second channels, 4- channel reproducing signals can be obtained merely by effecting the addition and subtraction of the first and second channel signals in a decoder device. This renders the decoder simpler in construction. Furthermore, even when a 4-channel matrix stereophonic record is reproduced using a stereophonic sound system, a clear image localization is obtained from the front signals. However, the encoding system suffers from the following disadvantages.
  • an encoding method in which, in coupling to respective first and second channels at least first and second sound input signals associated with front channels and at least third and fourth sound input signals associated with back channels to generate first and second channel signals, said first, second, third and fourth sound input signals are coupled to the first and second channels with such an amplitude relation that the amplitude levels of said first and third sound input signals included in said first channel signal are greater than those of the first and third sound input signals included in the second channel signal, and the amplitude levels of the second and fourth sound input signals included in said second channel are greater than those of second and fourth sound input signals included in the first channel signal, and in such a phase relation that the first and second sound input signals included in said first channel signal are in a substantially in-phase relation to the first and second sound input signals included in said second channel signal respectively and the third and fourth sound input signals included in said first channel signal is in a substantially opposite relation to the third and fourth sound input signals included in said second channel signal respectively: said encoding method comprising the steps of coupling said
  • FIG. 1 shows a model diagram for explaining an encoding system according to this invention
  • FIG. 2 shows vector diagrams of left and right channel signals L and R o'btainedby the encoding system of this invention with respect to respective input sound signals;
  • FIG. 3 shows vector diagrams of the left and right tion
  • FIGS. 4A 4B show vector diagrams of the left and right channel signals, respectively,.of front-center and back center signals;
  • FIGS. 5 to 7 show vector diagrams of the left and right channel signals obtained under respective blend conditions.
  • FIG. 8' shows a concrete example of the encoding system embodying this invention.
  • FIG. 1 shows a model of an encoding system according to this invention.
  • reference numerals 1 to 4 denote encoding input terminals to which sound signals L L R and R are respectively applied, and reference numerals 5 and 6 represent encoding output terminals from which a left channel composite signal L and right channel composite signal R are respectively derived out.
  • the sound signal L is coupled to the output terminal 5 through a phase shifter 7 for phase shifting an input signal by a reference angle d) at a relatively large amplitude level and an adder 11.
  • the sound signal R has its amplitude multiplied by a blend quantity A 1) due to the action of a blend resistor R i.e.
  • the sound signal L has a relatively large amplitude channel signals obtained under a certain blend condilevel and is coupled to the output terminal 5 through a phase shifter 8 for phase shifting an input signal by an angle equal to the reference angle plus 90 and the adder 11.
  • the sound signal R has its amplitude multiplied by a blend quantity A through a blend resistor R i.e. is coupled, at a relatively small amplitude level to the output terminal 5 through the phase shifter 8 and adder 1 l.
  • the sound signal R has a relatively large amplitude level and is coupled to the output terminal 6 through a phase shifter 10 having a phase shift characteristic similar to that of the phase shifter 7 and adder 12, while the sound signal L has its amplitude multiplied by a blend quantity A and is coupled to the output terminal6 through phase shifter 10 and adder l2.
  • the sound signal R is coupled to the output terminal plitude multiplied by a blend quantity A, and is coupled to the output terminal 6 through phase shifter 9 and adder 12.
  • the encoding system .of this invention has blend quantites A and A in addition to the blend quantity A More particularly, the signal L is coupled to the out put terminal 5 through the phase shifter 8 with the blend quantity A due to a resistor R and also coupled to the output terminal 6 through an inverter 13 and the phase shifter 9 with the blend quantity A due to a resistor R The signal L is coupled through the phase shifter 7 to the output terminal 5 with the blend quantity A and also coupled to the output terminal 6 through an inverter 14 and phase shifter 10 with the blend quantity A due to a reisitor 5.
  • the signal R is coupled through phase shifter 10 to the output terminal 6 with the blend quantity A and also coupled to the output terminal 5 through the inverter 13 and phase shifter 7 with the blend quantity A
  • the signal R is coupled through phase shifter 9 to the output terminal 6 with the blend quantity A and also coupled through inverter 14 and phase shifter 8 to the output terminal 5 with the blend quantity A
  • the inverters l3 and 14 are shown as of bidirectional type.
  • FIG. 2 shows vector diagrams of respective signals included in the right and left channel signals L and R obtained by the above-mentioned encoding system.
  • the amplitude ratio of respective input signals contained in the out ut si nals L and R is. as will be clearly shown, I +A w/A, +A
  • FIG. 3 shows the vector diagrams of the output signals L and R involved where A, A A 0.3063. In this case, the amplitude ratio of the respective input signals included in the output signals L and R is 1:0.414 as in the conventional system.
  • FIGS. 4A and 4B show vector diagrams of the output signals L and R respectively, involved when the front-center signal C (L R and bac k-center signal C (L R are encoded by the encoding system as described above.
  • the output signals L and R have the same phase and the same level, while in the case of the back-center signal C the output signals L and R have opposite phases and the same level. From the above it will be understood that the encoding system of this invention is suitable for use as a 4- channel matrix encoding system.
  • a phase difference of 28 present between the corresponding front input signals included in the above-mentioned output signals L and R may be safely taken as meaning that the respective front input signals are coupled, in substantially the same phase relation, to the left and right transmission systems.
  • a phase difference of 152 present between the corresponding back signals may be safely taken as meaning that the respective input signals are coupled, in a substantially opposite phase relation, to the left and right transmission systems.
  • the corresponding front input signals included in the output signals are caused to be entirely in phase and the corresponding back input signals to be entirely in opposite phase.
  • phase difference of about 19 exists between the output signals L and R and, therefore, the sound image localization of the front center signal becomes somewhat indistinct during 2-channel stereophonic reproduction.
  • the left and right-center signals 1 and R separation between the output signals L and R stays at 15.3 db. Generally, however, this separation is sufficient from the practical view point.
  • the output signals L and R are in phase and a phase difference between the front input signals is held down to 17.
  • separation of 16 db between output signals L and R and separation between the diagonal channels is 19.57 db.
  • encoding is effected to cause the output signals L and R to be in phase.
  • a phase difference between thee output signals becomes greater with respect to the frontcenter signal.
  • the output signals are caused to be in phase, a phase difference between the output signals becomes greater with respect to the respective front input signals.
  • a phase difference between the output signals L and R can be held down to about 10. More particularly a phase difference between the respective front input signals is l0.27 and a phase difference between the front-center input signals is 10.07.
  • left and right separation with respect to left and right-center signals L and R is about 17 db and a better compatibility is obtained with regard to a 2- channel stereophonic reproduction.
  • separation between the diagonal channels is 25.35 db.
  • the blend quantity A may be varied between the front and back directions; the blend quantity A; between the left and right directions and the blend quantity A between the two diagonal directions.
  • the blend quantities A A and A may take any value below unity.
  • FIG. 8 shows one example of an encoding system according to this invention in which elements identical to those shown in FIG. 1 are designated by the same reference characters, so that any detailed explanation is believed unnecessary.
  • the encoding system With the encoding system according to this invention, it is possible to optionally vary a phase difference between the respective input signals by varying the blend condition, and therefore it is possible to produce left and right channel signals having a compatibility practically sufficient for the conventional Z-channel stereophonic reproduction in respect of separation between the left and right channels, image localization involved in the case of front-center input signals and sound quality.
  • the encoding system can be of simple construction because phase shifters as used in the conventional encoding system can be used intact.
  • An encoding method in which, in coupling to respective first and second channels at least first and second sound input signals associated with front channels and at least third and fourth sound input signals associated with back channels to generate first and second channel signals, said first, second, third, and fourth sound input signals are coupled to the first and second channels with such an amplitude relation that the amplitude levels of said first and third sound input signals included in said first channel signal are greater than those of the first and third sound input signals included in the second channel signal and the amplitude levels of the second and fourth sound input signals included in said second channel are greater than those of second and fourth sound input signals included in the first channel signal, and in such a phase relation that the first and second sound input signals included in said first channel signal are in a substantially in-phase relation to the first and second sound input signals included in said second channel signal respectively and the third and fourth sound input signals included in said first channel signal is in a substantially opposite relation to the third and fourth sound input signals included in said second channel signal respectively: said encoding method comprising the steps of coupling said first sound input signal to said first

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Signal Processing (AREA)
  • Mathematical Physics (AREA)
  • Mathematical Analysis (AREA)
  • Mathematical Optimization (AREA)
  • General Physics & Mathematics (AREA)
  • Pure & Applied Mathematics (AREA)
  • Theoretical Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Algebra (AREA)
  • Multimedia (AREA)
  • Stereophonic System (AREA)
  • Stereo-Broadcasting Methods (AREA)
  • Compression, Expansion, Code Conversion, And Decoders (AREA)
US427932A 1973-09-18 1973-12-26 Encoding method for converting multi-channel sound signals into 2-channel composite signals Expired - Lifetime US3872249A (en)

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JP48105172A JPS5248002B2 (enrdf_load_stackoverflow) 1973-09-18 1973-09-18

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JP (1) JPS5248002B2 (enrdf_load_stackoverflow)
DE (1) DE2364997C3 (enrdf_load_stackoverflow)
GB (1) GB1397900A (enrdf_load_stackoverflow)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0880301A3 (en) * 1997-05-19 2001-01-03 Qsound Labs Incorporated Full sound enhancement using multi-input sound signals

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3787622A (en) * 1971-02-05 1974-01-22 Sansui Electric Co Quadrasonic sound system for two channel transmission
US3825684A (en) * 1971-10-25 1974-07-23 Sansui Electric Co Variable matrix decoder for use in 4-2-4 matrix playback system

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3745252A (en) * 1971-02-03 1973-07-10 Columbia Broadcasting Syst Inc Matrixes and decoders for quadruphonic records

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3787622A (en) * 1971-02-05 1974-01-22 Sansui Electric Co Quadrasonic sound system for two channel transmission
US3825684A (en) * 1971-10-25 1974-07-23 Sansui Electric Co Variable matrix decoder for use in 4-2-4 matrix playback system

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0880301A3 (en) * 1997-05-19 2001-01-03 Qsound Labs Incorporated Full sound enhancement using multi-input sound signals

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Publication number Publication date
JPS5057201A (enrdf_load_stackoverflow) 1975-05-19
JPS5248002B2 (enrdf_load_stackoverflow) 1977-12-07
DE2364997C3 (de) 1981-05-27
GB1397900A (en) 1975-06-18
DE2364997A1 (de) 1975-04-10
DE2364997B2 (de) 1980-07-03

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