EP0712264A2 - Method and apparatus for multi-channel sound reproduction - Google Patents

Abstract

The sound reproduction system uses at least 3 front sound reproduction channels positioned on the left and right and at the centre and 2 surround sound reproduction channels positioned on the left and right. Each of the received sound channel signals is divided, with one part provided with an increased delay time and an altered amplitude and phase before summation with the unaltered signal parts, for supplying summated signals to each of the sound reproduction channels. pref. auxiliary sub-sound reproduction channels (LSn,RSn) are supplied with further signals obtained by similar division and summation.

Description

The invention relates to a method of the type described in the preamble of claim 1 for processing multichannel source-oriented sound signals of a sound event, which can also be recorded, transmitted and matriculated between recording and playback, for the purpose of changing these signals before final amplification and radiation via a Loudspeaker arrangement with at least three front and two surround loudspeakers and a device suitable for this purpose, which is defined in more detail in the preamble of claim 4.

Such systems and associated display devices are described in ITU-R (formerly CCIR) recommendation BS.775 as well as in SMPTE standard PR 173 (1992) for a 3 / 2- or 3 / 4- or 3/2 / 1 system described.

Conventional two-channel stereo playback devices have so far been used predominantly for playback in living rooms and in small to medium-sized event or listening rooms, also in connection with image representations. With two-channel stereo playback, however, there was previously only a very small, tubular stereo listening zone with only one reference point. Another disadvantage of two-channel stereo playback is the imaging of a center signal with limited sound and location quality, which is only possible through the formation of phantom sources.

It is therefore also known to transmit a real center signal or real half-left and half-right signals (5-channel stereo) and to transmit them separately.

It is also known to provide the listener with room information in addition to the previously common two-channel stereo transmission and primary supply of direct information by means of a stereo reproduction device, which is either assigned or transmitted separately or in opposite phase, correlated or not correlated as side signals and transmitted via additional loudspeakers distributed in the room become.

The widespread efforts to summarize and transmit all these signals in a uniform format have led to the ITU-R recommendation BS.775 and the SMPTE standard PR 173 for a 3 / 2- (3/4) or 3 / 2/1 system.

Another proposal (Sony SDDS system) is the expansion to an 8-channel system (5 front and 2 surround channels as well as a sub-bass channel)

It should also be borne in mind that multichannel sound transmissions should be coupled with the introduction of new television transmission systems.

It is also known that the multi-channel sound system Dolby Stereo Surround has been used for years in the film industry. This 3-plus-1 system (3 front channels and 1 surround channel nested in 2 transmission / recording channels) is also available for home use. The advantages of a center loudspeaker in this three-channel matrix transmission of front or primary information have also been proven in this system, despite the matrix circuit used with regard to the two-channel film.

The difference between this Dolby stereo surround system and the recommendations mentioned is a discrete one Center channel mainly in the different number of surround channels.

Studies have proven that two decorrelated spatial information guarantee a much better supply than the previously practiced channel.

In order to reduce the disadvantages, particularly with regard to the insufficient supply of room information, two playback speakers for the two-channel room information were created, similar to the practice common at first with the stereo ambiophony system according to Keibs (1960) for two- or single-channel room information or also similar to the later practice with the Dolby stereo surround system with single-channel spatial information, integrated into the overall display arrangement. But this variant also only brings significant advantages in the overall impression if the defects in the directional assignment and the previously inadequate provision of the listener seats are overcome.

The shortcomings of the single-channel reproduction of spatial information have recently been taken up again and, in addition to the acceptance of the ITU and SMPTE standards, have led to new film sound processes, in which two-channel spatial information is used in each case.

There are also known two-channel stereo reproducing arrangements in which the low-frequency reproduction (up to approx. 120 Hz) takes place separately from the directional signals by means of separate loudspeakers, so-called subwoofers, in order to limit the physical size of the individual loudspeakers. When applied to the aforementioned international recommendations, a 3/2/1 system or a maximum of 5/2/1 system results.

Sound signal reproduction so perfected shows an improvement in the reproduction quality with regard to the imaging of now three (or more) front information and regarding the spatial information within a slightly enlarged listening zone.

Outside this defined hearing area, which is very small in relation to the total room size, location errors have a considerably more disruptive effect. The distributed front signals are not shown in the correct direction, but are only heard from the nearest loudspeaker. The two spatial information is perceived to a large extent in a differentiated manner depending on the location.

Although it is also known to optimally supply large auditoriums (DE 3413 181), this requires separate source treatment and therefore a very high outlay which is disproportionately large for transmission and for small rooms.

When playing back at home, the disadvantage of the insufficient listening area, in particular in connection with high-quality picture reproduction, is serious, however, since the space dependency means too great a restriction and also has a major impediment to the introduction of these methods in the home area.

This multitude of suggestions and recommendations for different applications and their constant expansion confirms the inadequacy of the known methods described and the need to create a more generally applicable solution for the improved reproduction of multichannel sound systems.

The object of the invention is therefore to make it possible for transmitted and recorded two-channel and multi-channel stereo signals to enlarge the defined listening zone for the space-independent reproduction of the spatial information while at the same time maintaining the specified directional information of the individual audio signal sources . The should Loudspeakers can receive favorable placements within the location distribution possibilities given by the space limits.
At the same time, the proportion of the total room size for acoustic / visual usability should be increased. This also applies to larger rooms. It should be taken into account that by converting available program materials with less than 5 channels, pseudo-multi-channel playback conditions should be created.

This object is achieved with the procedure described in the characterizing part of patent claim 1.

Advantageous developments of the method are described in claims 2 and 3.

A device that is particularly suitable for performing this method is described in the characterizing part of patent claim 4.

Developments of this device are described in claims 6 to 9.

Fig. 1

einen Vergleich der Stereo-Hörzonen bei üblicher 5-Kanal-Wiedergabe und bei Anwendung der Erfindung (schraffierter Bereich);

Fig. 2

die Grundstruktur der Vorrichtung mit den Funktionseinheiten Eingangsstufen E, Eingangsmatrix EM, Bearbeitungsstufen FD, Summier- und Pegeldosierungsstufen SE, Ausgangsmatrix AM, "intelligente" Eingabe EA und einer Anzeige;

Fig. 3

eine Ergänzung durch die Funktionseinheit Konvertierungsmatrix KM;

Fig. 4

eine Ergänzung mit den Funktionseinheiten FE für die Erzeugung eines Tiefsttonkanals zur getrennten Ansteuerung eines sog. Subwoofers;

Fig. 5

eine weitere mögliche Ergänzung der Bearbeitungsmöglichkeit jedes Eingangssignals für ergänzende Wiedergabekanäle bei größeren Räumen;

Fig. 6

eine Konfiguration für die Bearbeitungsmöglichkeit aller Kanäle.

The invention is explained in more detail below on the basis of exemplary embodiments. In the accompanying drawings, the

Fig. 1

a comparison of the stereo listening zones in conventional 5-channel playback and when using the invention (hatched area);

Fig. 2

the basic structure of the device with the functional units input stages E, input matrix EM, processing stages FD, summing and level metering stages SE, output matrix AM, "intelligent" input EA and a display;

Fig. 3

supplemented by the functional unit conversion matrix KM;

Fig. 4

a supplement with the functional units FE for the generation of a low-frequency channel for the separate control of a so-called subwoofer;

Fig. 5

a further possible addition to the processing possibility of each input signal for additional playback channels in larger rooms;

Fig. 6

a configuration for editing all channels.

The main effect of the invention is the enlargement of the stereo listening zone shown in FIG. 1 while maintaining the complex auditory impression to be achieved, which was reduced to a single reference point in the previous two-channel stereophonic system and in the standardized multichannel sound arrangement (3/2 arrangement). allows only a small enlargement of the listening zone, taking into account the standard arrangement.

A further significant advantage in the application of the invention results from the placement of the loudspeakers in the respective individual reproduction area, which is not rigidly bound to the standard arrangement.

• der Eingangsmatrix EM mit den davorliegenden Eingangsstufen E,
• den Funktionseinheiten FD zur mehrkanaligen, unabhängigen Laufzeit-, Pegel- und ggf. erforderlichen Phasenkorrektur,
• den Summierstufen SE und
• der Ausgangsmatrix AM.

In order to enable the advantageous reproduction of program contributions that are transmitted using one of the matrix methods, for example by means of the Dolby stereo surround system, a device using the method described is required after the decoder that is usually used (eg Dolby Pro Logic Surround Decoder). which - depending on the wishes and ideas of the user - can process a five- or 5-plus-1-channel program as well as other single- or multi-channel programs.
The loudspeaker arrangement available for multi-channel playback and set up in a room in compliance with the standard and the available possibilities is supplemented by a device which is designed for a radio and / or TV receiver or a playback device for multi-channel Sound recordings and before the power levels of the individual speakers must be switched.
According to FIG. 2, it consists of:

• the input matrix EM with the input stages E in front of it,
• the functional units FD for multi-channel, independent runtime, level and possibly necessary phase correction,
• the summation stages SE and
• the output matrix AM.

The inputs of the input stages (1-n) are thus connected to the outputs of a multi-channel receiver or other single- or multi-channel program sources. The outputs of these input stages are connected to the inputs of the input matrix EM. This distributes the existing input signals over the connections to the functional units FD, so that each FD receives n-1 of the available input signals. The (n-1) outputs of each FD are connected to the inputs of a summing stage SE. An unprocessed input signal reaches each summing stage via a direct connection between the input matrix EM and each summing stage SE, so that a summing signal can be formed from the n input signals in each SE.

These sum signals differ in that differently processed signals and an unprocessed signal from the number of signals available on the input side are present in each sum signal.

The outputs of the summing stages SE - which contain the possibility of controllable level influencing on the output side - are connected to the output matrix AM, so that they are connected to the existing connected playback channels, ie to the inputs of the power amplifiers and via the output matrix can be assigned to the corresponding playback channels.
When taking into account the multi-channel playback of a program with fewer than 5 signals, a conversion matrix KM, which distributes the existing input signals to the input matrix EM, can lie in front of the input matrix EM according to FIG. 3 in addition to this functional complex.

In this case, the outputs of the input stages E are connected to the inputs of the conversion matrix KM and their outputs to the corresponding inputs of the input matrix EM.

If a separate bass channel is not included in the program signal, a filter unit FE-1 can be connected to the outputs of the input stages E in accordance with FIG. 4 in order to produce a separate bass channel. In this, as is also known, the low-frequency signal components are filtered out, summed and assigned to a separate low-frequency channel via a low-pass circuit from the existing input signals, preferably the three front signals.

In order to adapt the speakers to the existing room conditions, a further filter module FE-2 of the output matrix can be connected downstream of the output matrix for the playback channels, as already practiced in stereo playback in high-quality home playback systems (FIG. 4).

An input unit EA must be assigned to this special device to acoustically optimize this playback arrangement to the existing room conditions, locations of the loudspeakers and the desired listening zone. This enables the location of the speakers, their parameters, the existing room conditions and the desired listener positions to be entered, as well as the possibility of correcting and adjusting the conditions between direct information and desired room information (R / D) depending on the program material.

In terms of control, this input arrangement EA is connected to the individual assemblies of the entire device and controls the variably adjustable parameters of the individual assemblies. It automatically calculates parameters based on the entered room and location parameters and assigns them to the corresponding modules.

In order to visually check the entered parameters, a display is provided as a supplement to the input arrangement.

When supplying larger listening zones, additional functional units FD are inserted, the inputs of which are connected to all outputs of the input matrix EM and thus a sum signal from all - but differently treated - input signals for each further playback channel 1 to m, which is connected to further distributed loudspeakers , is formed (Fig. 4).

This permissible extension of the device - each input signal, including the signal that is not to be processed, reaches the summing stage via an FD - simplifies the circuitry solution of this device, as shown in FIG. 6.

The signal flow for a 5-channel program can be explained as follows:
The signals pass from the source (transmission channel, multi-channel recording, etc.) to the input stages E of this special device. They are distributed to the existing functional units FD by means of the input matrix in such a way that four of these 5 available input signals are assigned to each FD, so that one signal in each FD is not one Parameter correction is subjected. (In the first FD, the first signal is switched unprocessed to the subsequent summing stage SE, in the second FD the second, etc.).

In the downstream summing stage SE, the four signals treated differently in terms of level, transit time and phase and the untreated signal in each case are summed again and the level is corrected together. At the output of the output matrix AM, these sum signals are assigned to the existing playback channels and the loudspeakers connected to them with their power levels in accordance with their function definition (front loudspeaker surround loudspeaker).

In a permissible extension of the device, the functional units FD can be expanded in such a way that they enable a parameter change for all input channels, so that a sum of all available and treated input signals is created for each playback channel (FIG. 6).
If a filter device FE-1 is connected downstream of the input stages, the low-frequency components of the individual unprocessed source signals are filtered out, summed in the SE and assigned to a separate woofer channel, which supplies a special woofer with a corresponding power unit via a level correction unit.

The placement of the loudspeakers, which does not always conform to the standard, and the optimal location of the listener, which can hardly be maintained in practice, as well as the spatial home conditions, require in most applications a frequency response correction of the loudspeakers adapted to the respective room and the desired listening zone and, if necessary, a runtime correction of the playback channels depending on their Location. The latter can be done in the FD.

4 and 5, the signals at room correction filter modules FE-2 can be switched between the output matrix AM and the inputs of the power amplifiers of the playback channels for a necessary spatial adaptation of the frequency response.

These room correction filters make it possible to adapt the timbre of the entire display arrangement by changing the individual display channels, the respective room and the ideas of the user by entering correction values.

The deviations from a standard list can be corrected by entering the location parameters in the input unit. By entering further parameters such as loudspeaker data, listening zone or listener positions, etc., volume ratios can be corrected and the listening conditions outside of an optimal listener position, in particular in the preferred range (preferred listener position) of the user, can be optimized.

The relationship between the direct component and the surround component can also be changed depending on the program material by entering appropriate correction values in the existing input unit, stored and retrieved in association with the current program.

The use of this device also for the reproduction of program material with less than five audio channels is made possible by the conversion matrix KM connected upstream of the input matrix EM.

Claims (9)

Method for multi-channel sound reproduction, in which the sound signals of a sound event are recorded in a multi-channel, source-oriented manner, in which further steps of the recording, transmission and matrixing of the further processing for the purpose of changing these signals can be upstream and in which these signals prior to the final amplification and emission to at least three front and two surround channels and optionally also be distributed to a sub-bass channel, characterized in that after the distribution of the existing multichannel audio signal or after the assignment of a smaller number of signals to the at least three front and two surround channels of each of these signals divided and a part with an increased transit time, a reduced level, if necessary changed phase position and a summation with one of the five or more different, unchanged signal components is supplied that the sum signals ent in accordance with the directional assignment of the respective unchanged signal components to the three front and the two surround playback channels and preferably after further similar divisions and summations, to channels of further playback speakers arranged in the room. Method according to Claim 1, characterized in that the additional surround loudspeakers are supplied with further summing signals which are each formed from one of the five (or more) signals corrected differently in terms of transit time, level and, if necessary, phase, and a further signal, its additional amplitude reduction and increase in transit time is carried out according to the distance from the location of the first two surround speakers and the assigned coverage area of said additional surround speakers. Method according to Claim 1, characterized in that a summation of signals processed exclusively in this way is also carried out, in which a processed signal is formed from each input for each output. Device for multi-channel sound reproduction with five (or more) input connections for preferably three front and two surround signals, in which the five (or more) inputs of a matrix, each having an input stage, are connected to the corresponding input connections, characterized in that the outputs of the Matrix (M) on the one hand is due to the same number of input connections of a functional unit (FD) for the respectively separate, different correction of the fed signals with regard to transit time, level and possibly phase for each output of this functional unit (FD) and on the other hand with the first inputs of a summing unit (SE) are connected, with the second or further inputs of which the outputs of the functional unit (FD) are connected, and that the sum signals formed from an unchanged input signal at the input stage (E) with differently processed signals from other input signals correspond accordingly the assignment of the unchanged input signals to the outputs of the matrix (M) for the preferably three (or more) front and two surround channels. Apparatus according to claim 4, characterized in that the matrix (M) is preceded by a further conversion matrix (KM), which converts the existing audio signals from recordings or transmissions with fewer than five audio channels (mono, 2-, 3-, 4-, 5 / 2-channel stereo surround method) distributed over the five (or more) input stages of the matrix (M). Apparatus according to claim 4, characterized in that, in the absence of a separate sub-bass transmission or recording channel, the matrix (M) is preceded by a multi-channel filter unit which contains low-pass circuits (TP) and a summing stage and which filters out, sums and sums the low-frequency components of the existing audio channels assigned to a separate sub-bass channel, to the output of which subwoofers are connected. Apparatus according to claim 4, characterized in that the functional unit (FD) is provided with an input arrangement (EA) for the input of the spatial conditions of the playback arrangement (loudspeaker positions) and the desired parameters (volume ratios of front and surround loudspeakers). Device according to Claims 4 and 7, characterized in that the input arrangement (EA) is assigned a display which shows the inputs and the parameters to be changed (runtime correction, level correction, correlation degree correction, etc.). Device according to claims 4 and 7, characterized in that the input arrangement (EA) for further parameters of the sound signals to be influenced is provided and is therefore connected to the units (KM, FE, SE. M) which influence the sound signal paths via their processing elements including the required parameter values from the entered room parameters and individual specifications.

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