Abstract: A sound processing system increases the robustness of surround sound in various playback situations. The system may process an incoming signal, such as a five channel surround sound signal, with a first and a second matrix. The first and second matrices produce outputs signals from the input incoming signals. At least one of the output signals may be combined before being sent to the speakers.

Abstract: A lossless audio codec segments audio data within each frame to improve compression performance subject to a constraint that each segment must be fully decodable and less than a maximum size. For each frame, the codec selects the segment duration and coding parameters, e.g., a particular entropy coder and its parameters for each segment, that minimizes the encoded payload for the entire frame subject to the constraints. Distinct sets of coding parameters may be selected for each channel or a global set of coding parameters may be selected for all channels. Compression performance may be further enhanced by forming M/2 decorrelation channels for M-channel audio. The triplet of channels (basis, correlated, decorrelated) provides two possible pair combinations (basis, correlated) and (basis, decorrelated) that can be considered during the segmentation and entropy coding optimization to further improve compression performance.

Abstract: Sound processing systems have been developed that create a surround effect without quality degradation experienced by known sound processing systems in non-optimum listening environments. The sound processing systems may include matrix decoding systems that manipulate input signals prior to converting them into a number of output signals so that the output signals are a function of a greater number of input signals. These sound processing systems may also or alternately include a bass management system that from the input signals preserves the low frequency components of the input signals in separate channels. Both the matrix decoding systems and bass management systems may also produce additional signals. Further, the matrix decoding and bass management systems may be implemented separately or jointly in vehicular sound systems.

Abstract: A multi-channel audio reproduction apparatus and method for loudspeaker reproduction using virtual sound images whose positions can be adjusted is provided. The multi-channel audio reproduction apparatus includes a virtual sound image forming unit for compensating for the occurrence of cross-talk in at least one input audio signal according to the arrangement of loudspeakers, obtaining transfer functions occurring when sound from a position in a three dimensional space is transmitted to both ears of a listener, and forming a plurality of first virtual sound images in a three dimensional space using the transfer functions. A controller generates adjusting factors for adjusting the position of at least one second virtual sound image.

Abstract: The present invention provides improvements to prior art audio codecs that generate a stereo-illusion through post-processing of a received mono signal. These improvements are accomplished by extraction of stereo-image describing parameters at the encoder side, which are transmitted and subsequently used for control of a stereo generator at the decoder side. Furthermore, the invention bridges the gap between simple pseudo-stereo methods, and current methods of true stereo-coding, by using a new form of parametric stereo coding. A stereo-balance parameter is introduced, which enables more advanced stereo modes, and in addition forms the basis of a new method of stereo-coding of spectral envelopes, of particular use in systems where guided HFR (High Frequency Reconstruction) is employed. As a special case, the application of this stereo-coding scheme in scalable HFR-based codecs is described.

Abstract: An L-channel signal and an R-channel signal are input into a subtractor in which the difference between the L-channel signal and the R-channel signal is determined. The resulting signal is input into first and second multipliers. In the first multiplier, a mixed output signal is generated by using the channel mixture ratio calculated in a previous frame. In the second multiplier, a mixed output signal is generated by using the channel mixture ratio calculated in a current frame. The mixed output signals from the first and second multipliers respectively undergo spectrum transform in first and second spectrum transformers, and quantized in first and second quantizers. A comparator compares a quantization error in the first quantizer with that in the second quantizer. If the quantization error in the second quantizer is greater than that in the first quantizer by a predetermined factor, the comparator controls a switch to select the output of the first quantizer.

Abstract: Inputting of a parametrically encoded audio signal comprising at least one combined signal of a plurality of audio channels and one or more corresponding sets of side information describing a multi-channel sound image and including channel configuration information is shown along with deriving, from the channel configuration information, audio source location data describing at least one of horizontal and vertical positions of audio sources in the binaural audio signal; selecting, from a predetermined set of head-related transfer function filters, a left-right pair of head-related transfer function filters matching closest to the audio source location data, wherein the left-right pair of head-related transfer function filters is searched in a stepwise motion in a horizontal plane; and synthesizing a binaural audio signal from the at least one processed signal according to side information and the channel configuration information.

Abstract: A method of mixing audio channels is effective at rebalancing the audio without introducing unwanted artifacts or overly softening the discrete presentation of the original audio. This is accomplished between any two or more input channels by processing the audio channels to generate one or more “correlated” audio signals for each pair of input channels. The in-phase correlated signal representing content in both channels that is the same or very similar with little or no phase or time delay is mixed with the input channels. The present approach may also generate an out-of-phase correlated signal (same or similar signals with appreciable time or phase delay) that is typically discarded and a pair of independent signals (signals not present in the other input channel) that may be mixed with the input channels. The provision of both the in-phase correlated signal and the pair of independent signals makes the present approach well suited for the downmixing of audio channels as well.

Abstract: An active audio matrix decoding method and apparatus to generate multi-channel audio signals from a stereo channel audio signal. The method includes: decoding a stereo channel audio signal into a multi-channel signal, extracting a power vector of each channel signal by multiplying a magnitude of each decoded channel signal by positions of a plurality of channel speakers, extracting a vector of a virtual sound source existing between each channel by linearly combining power vector values of each decoded channel, extracting a vector value of a dominant sound image by linear combination of the vectors of the extracted virtual sound sources and normalizing the position of each channel speaker with respect to the vector value of the dominant sound image, and distributing a gain value to each channel position by comparing the magnitude of an entire decoded channel signal with the magnitude of each channel signal.

Abstract: In a multi-channel acoustic apparatus with a DVD reproduction function, comprising a DVD reproduction control unit for controlling the reproduction of a DVD, and a system control unit for controlling the overall acoustic apparatus and controlling the reproduction of another input source other than the DVD, the DVD reproduction control unit comprising the function of controlling a first Dolby Pro Logic decoder which can be used at the time of reproducing the DVD, and the system control unit comprising the function of controlling a second Dolby Pro Logic decoder which can be used at the time of reproducing the input source other than the DVD, there are provided means for adjusting a surround delay time period on the basis of a user operation, and means for transmitting to the system control unit the adjusted surround delay time period.

Abstract: A sound processing system adaptively mixes active matrix decoding and passive matrix processing of incoming audio signals. Mixed output signals are generated with active matrix decoding where the audio signals are stereo. Mixed output signals are generated with passive matrix processing where the audio signals are monaural. The sound processing system reduces the degree of active matrix decoding in the mixed output signals where the incoming audio signals are stereo and monaural. The sound processing system also generates virtual stereo signals from incoming audio signals having monaural signals. Mixed output signals are generated of the virtual stereo signals using active matrix decoding.

Abstract: An audio system for a vehicle that includes a first passenger location and a second passenger location, the second passenger location situated behind the first passenger location, the audio system including a first directional audio channel signal source; a surround audio channel signal source; a first electroacoustical transducer coupled to the first directional audio signal source and to the surround audio channel source, situated forward of the second passenger location and behind the first passenger location. The first electroacoustical transducer radiates sound waves corresponding to audio signals from the first directional audio channel signal source and corresponding to audio signals from the surround audio channel signal source. The system further includes a second electroacoustical transducer coupled to the first directional audio signal source, situated forward of the first electroacoustical transducer.

Abstract: A method and apparatus for processing multi-channel audio signals in which the channels are processed by one of alternatively selectable processes to produce an alternatively selectable number of output channels, the process being responsive to information contained in the input signal.

Abstract: A sound reproduction system has been developed, for converting signals on two input channels into surround signals on five or seven output channels and vice-versa. A decoder is included in the sound reproduction system which enhances the correlated component of the input signals in the desired direction and reduces the strength of such signals in channels not associated with the encoded direction, while preserving the apparent loudness of all output channels, the separation between the respective left and right output channels and the total energy of the uncorrelated component of the input channels in each output channel. The decoder may include a uniquely defined matrix that helps to ensure that the surface of the output signals is smooth and continuous.

Abstract: The inventive mechanism uses several sub-systems to generate outputs from the stereo input signal. A first sub-system synthesizes the phantom center output, which places the monaural center image between the left and right speakers in front of the listener. A second sub-system synthesizes the virtual surround (or rear) output signals, which places the sound images to the sides of the listener. A third sub-system synthesizes the left and right stereo outputs, and expands the locations of the left and right sound images.

Abstract: A multidirectional audio decoder using an “adaptive” audio matrix derives at least one of a plurality of output audio signals from two or more directionally-encoded audio input signal streams (S1(?), S2(?), . . . SN(?), wherein ? is the encoded angle of a source audio signal. Each output signal is associated with a principal direction ?. In order to generate each output signal, a pair of intermediate signals (“antidominant” signals) are generated, constituting the antidominant signal for each of the two adjacent principal output directions of the decoder. The antidominant signal for any arbitrary principal (or “dominant”) direction is the combination of input signals having coefficients such that the combination goes to zero for that dominant direction. Amplitude control is applied to the two antidominant signals to deliver a pair of signals having substantially equal magnitudes that are additively or subtractively combined to provide the output audio signal associated with a principal direction.

Abstract: A vehicle audio system has an audio central unit to which one or more further audio components are connected via an associated first data bus, and are interfaced for data communication between the first data bus and a second data bus of another type in the vehicle. One of the audio components is an audio gateway unit which contains the interface, and is an independent component separate from the audio central unit. In addition to the data bus gateway functions, the audio gateway unit includes further standard audio functions spanning vehicle types or countries, or further audio functions which are implemented so as to be parameterizable according to specific vehicle type and/or country.

Abstract: The present invention improves the stability of aural images in the decoding of multichannel signals. Output center-channel and back-surround channel signals are derived or augmented by applying signal processors such as matrix decoders to multichannel input signals.

Abstract: The present invention includes a gaming machine with a first control module that includes a main processor for randomly selecting one of a plurality of outcomes of said gaming machine in response to a wager amount and for sending audio information that controls audio output from the gaming machine. An audio control module is separate and distinct from the first control module, and includes an audio processor that receives the audio information from the main processor. The audio control module is coupled to an audio speaker system for broadcasting the audio output corresponding to the audio information. Also, the first control module may include a memory device that stores operating instructions for the gaming machine, while the audio control module may include an audio memory device for storing audio data sets that the audio processor processes to produce the audio output.

Abstract: A system and method is disclosed to remove cross talk terms from speech signals in a multi-party conference system using an estimator to first estimate the respective cross talk terms for each of the said plurality of users. In one embodiment, these terms are then multiplied with a filter based on the estimated cross talk terms. Source speech signals may thereby be recovered from the plurality of multi-party conference users without the cross talk.

Abstract: Three surround sound channels are provided within the current formats of the Dolby Digital, Sony SDDS and DTS digital soundtrack systems in a manner that provides compatibility with conventional two surround channel playback in standard 5.1 channel and 7.1 channel systems while allowing the soundtrack preparer to send the same signal to all surround sound channels and preserving the ability to pan among the three matrix decoded surround sound channels in an arrangement that employs an active matrix decoder to provide the three surround sound channels.

Abstract: A method derives at least three audio signals, each associated with a direction, from two input audio signals. In response to the two input signals, a passive matrix generates a plurality of passive matrix audio signals, including two pairs of passive matrix audio signals, a first pair of passive amtrix audio signals represent directions lying on a first axis and a second pair of passive matrix audio signals represent direction lying on a second axis, the first and second aces being substantially at ninety degrees to ach other. The pairs of passive matrix audio signals are processed to derive a plurality of matrix coefficients therefrom, The processing includes deriving a pair of intermediate signals and urging each pair of intermediate signals toward equality in response to a respective error signal. At least three output signals are produced by matrix multiplying the two input signals by the matrix coefficients.

Abstract: A sound reproduction system has been developed for converting signals on two input channels into surround signals on five or seven output channels and vice-versa. A decoder is included that enhances the correlated component of the input signals in the desired direction and reduces the strength of such signals in channels not associated with the encoded direction, while preserving the apparent loudness of all output channels, the separation between the respective left and right output channels and the total energy of the uncorrelated component of the input channels in each output channel. Included within the decoder is a uniquely defined matrix that helps to ensure that the surface of the output signals is smooth and continuous. An encoder is also included which encodes five or seven channels of sound into two so the two channels may be decoded by a variety of decoders with the correct sound direction and level.

Abstract: Sound processing systems have been developed that create a surround effect without quality degradation experienced by known sound processing systems in non-optimum listening environments. The sound processing systems may include matrix decoding systems that manipulate input signals prior to converting them into a number of output signals so that the output signals are a function of a greater number of input signals. These sound processing systems may also or alternately include a base management system that from the input signals preserves the low frequency components of the input signals in separate channels. Both the matrix decoding systems and base management systems may also produce additional signals. Further, the matrix decoding and base management systems may be implemented separately or jointly in vehicular sound systems.

Abstract: A sound reproduction system has been developed, for converting signals on two input channels into surround signals on five or seven output channels and vice-versa. A decoder is included which enhances the correlated component of the input signals in the desired direction and reduces the strength of such signals in channels not associated with the encoded direction, while preserving the apparent loudness of all output channels, the separation between the respective left and right output channels and the total energy of the uncorrelated component of the input channels in each output channel. Included within the decoder is a uniquely defined matrix that helps to ensure that the surface of the output signals is smooth and continuous. An encoder is also included which encodes five or seven channels of sound into two so the two channels may be decoded by a variety of decoders with the correct sound direction and level.

Abstract: An encode/decode 5-2-5 matrix system is combined with a discrete digital, multi-channel audio system to expand the number of independently addressable output channels. One embodiment of the system provides additional output channels by matrix encoding the additional audio information into the rear surround channels of a discrete digital five channel surround system. The expanded channels provide additional center surround and left and right overhead outputs. The 5-2-5 matrix channel separation is improved by increasing the surround channel attenuation when no dominant surround signal is present in the input to the 5-2-5 matrix decoder. In a second embodiment the system provides a surround encode/decode system offering eleven independently addressable output channels.

Abstract: A car-borne sound system that reproduces a recorded multi-channel music source in the 5. 1 system or the like system into a natural sound environment in a room of an automobile. Conventionally, at a driver's seat or at a front passenger seat, a sound image of vocal sounds (singing voice) was locating deviated from the natural placement. The present sound system eliminates such unnatural sound image positioning. A front center signal and a front right and a front left signals, which include much of the vocal components, are added on to a rear right and a rear left signals so that rear speakers (106 and 107) also reproduce the vocal components. Thus the vocal sound image is placed and fixed in the central place to provide a natural listening environment.

Abstract: A method and apparatus for preserving matrix-surround information in encoded audio/video includes a receiver operative to receive matrix-surround encoded audio signals via a modem, separate the audio signals into a frequency spectrum having discrete audio frequencies, and determine a cutoff threshold used to encode the matrix-surround encoded audio signals. The method and apparatus further includes a decoder operative to decode a first set of the audio frequencies below the determined cutoff threshold using a first matrix-surround preserving audio encoding method and to decode a second set of audio frequencies above the cutoff threshold using a second non matrix-surround preserving audio encoding method.

Abstract: A sound processing system increases the robustness of surround sound in various playback situations. The system may process an incoming signal, such as a five channel surround sound signal, with a first and a second matrix. The first and second matrices produce outputs signals from the input incoming signals. At least one of the output signals may be combined before being sent to the speakers.

Abstract: The method and system of present invention sequences audio post-processing algorithms to simulate live or theater sound. An audio signal is selectively post-processed according to equipment availability and listener preferences. Downmixing or Prologic algorithms are applied to a signal arriving at sound system. A listener inputs their speaker configuration to a player console. Desired post-processing effects are likewise indicated to the console. For instance, if surround sound equipment is both available and selected, then surround portions of the audio signal are parsed to surround speakers. Bass management techniques then transfer low frequency channels of the signal to compatible speakers. VES or DCS algorithms further manipulate the surround portion of the signal to create an illusion of immersion, and a center channel equalizer balances the signal playback. Alternatively, the post-processed signal is transmitted to a headphone set.

Abstract: An apparatus for recording a multichannel program includes an audio converter adapted to convert said multichannel program at least partially into a modified program requiring less channels than said multichannel program. The audio converter including control elements used to modify the conversion process used to generate said modified program. A coefficient generator coupled to said converter to generate a coefficient indicative of the operation of said controls. A mixer is arranged to mix the coefficient with program data. A recorder is arranged to record the mixed data on a medium, whereby the medium can be played either using a multichannel player device or a reduced channel player device by using said coefficient.

Abstract: An encoding device converts four-channel or five-channel audio signals to two-channel audio signals, which are then subjected to compression in accordance with the MPEG standard. Matrix coefficients are calculated based on the two-channel audio signals. A decoding device receives the compressed two-channel audio signals together with the matrix coefficient. The compressed two-channel audio signals are expanded and are then subjected to prescribed arithmetic operations using the matrix coefficients. Thus, the decoding device reproduces the original audio signals. The decoding device, which is normally actualized by a digital signal processor (DSP), is noticeably reduced in amounts of calculations and is simplified in circuit configuration because of the elimination of calculations of matrix coefficients therein.

Abstract: A multi-channel stereo converter is described comprising stereo magnitude determining means for generating a stereo information signal (a/b; &rgr;), which represents a degree of stereo between audio input signals (L, R), and transforming means for transforming said audio signals (L, R) based on said stereo information signal (a/b; &rgr;) into at least a surround signal (S). A space mapping interpretation is presented and an audio centre signal may be derived from the stereo input signals as well. The result is more flexibility in application and design, without substantial cross talk in the audio signals.

Abstract: For audio coding, the MPEG-2 standard provides for a spatial representation by multi-channel reproduction. In order to ensure backwards compatibility with MPEG-1 signals, the signals of the multi-channel sound channels are matrixed. Before being matrixed, the audio signals generally have their levels reduced in order to prevent overdriving. In order to balance again the reduction at the encoder end, an option that is provided in the MPEG-2 standard is for a decoder to raise the output levels again. If, however, a transmission error then occurs in the multi-channel section, the decoder cannot carry out the reverse matrixing. In that case, only the MPEG-1-compatible signal component will be decoded. The auditory impression can therefore be disturbed in various ways during the changeover to MPEG-1 decoding.

Abstract: A system for extracting a bass signal from left and right audio input signals of a stereo signal including a differencing circuit generating a difference mode signal from the left and right audio input signals; a detector circuit generating a first coefficient of proportionality that is a function of the relative phase of the left and right input signals; and a first multiplier circuit multiplying the first coefficient of proportionality times the difference mode signal to produce a modified difference mode signal, wherein the modified difference mode signal is used to generate the bass signal.

Abstract: The system and method of the present invention provides enhanced surround sound effects. In one embodiment, 90.degree. phase shift and copy of the modified head related transfer functions (HRTF) are applied to each rear sound signal. The modified HRTF for each rear signal is generated by removing the head related transfer function corresponding to the front center signal from the HRTF corresponding to the rear sound signal. This provides the audible effect of distinguishing more clearly sounds originating in front of the listener or to the rear of the listener while not limiting the perceived bandwidth of the signal. The rear signals corresponding to the first channel are inverted. The front and rear signals for each corresponding channel are then combined. The two channels, generated can be stored on media, such as film, and subsequently read and input to a surround sound decoder to generate enhanced surround sound output.

Abstract: A surround sound system for personal computer includes a control card and a PC surround decoder. The control card is a PC interface card for interfacing to the personal computer and draining the 5 VDC and .+-.12 VDC power from the personal computer as power source for both the control card and the PC surround decoder to operate. The PC surround decoder for processing the stereo source signal and generating left, center, right, surround and subwoofer signals. A connecting means electrically connects the PC surround decoder to the control card. The PC surround sound system is specified for incorporating with personal computer which enables the users to command the PC surround sound system with their computer keyboard or mouse and receive the full benefit of Dolby Surround encoded multimedia software and the like.

Abstract: A surround sound apparatus wherein a decoder decodes directionally encoded audio signals for reproduction via a loudspeaker layout over a listening area wherein the signals are decoded by a matrix. The coefficients of the decoding matrix are such that at a predetermined listening position, the reproduced velocity vector direction and the reproduced energy vector position directions are substantially equal to each other and substantially independent of frequency in a broad audio frequency range The gain coefficients of the decoding matrix are such that the reproduced velocity vector magnitude varies systematically with encoded sound direction at frequencies in the region of and above a predetermined middle audio frequency.

Abstract: A matrix decoding system and method generates left, right, center and surround output signals by adding and subtracting weighted versions of first and second input signals. The output signals are generated using a variable matrix to combine the input signals. The variable matrix is controlled by steering control signals derived from a controller which generates the steering control signals responsive to the detected phase difference between the first and second input signals. The decoding system and method uses compressors to generate constant amplitude versions of the input channels prior to performing phase detection. Because the compressors generate constant amplitude signals, phase detection is not affected by an imbalance in channel power.

Abstract: A frequency-dependent linear audio signal processor takes source signals S in input signals and provide directionally spread directionally encoded output signals. The processor directionally encodes with constant gain magnitude frequency components of the source signal S to-and-fro across a predetermined directional stage P" as frequency increases such that at least three predetermined positions within the stage P", the directional encoding has substantially zero perceived phasiness. The processor may be a frequency-dependent rotation matrix for stereo input signal and may be a unitary network using a feedback path around parallel identical all-pass networks in series with a rotation matrix and a feedforward path bypassing the all-pass networks. Successive frequencies of positioning of source signal S at a predetermined position P within the stage P" are preferably spaced approximately uniformly on a logarithmic or Bark Frequency scale.

Abstract: An improved theater surround sound system incorporates a screen top speaker and an overhead speaker driven by corresponding upper surround channels to more accurately reproduce sounds produced from above the listener. These top surround channels are encoded along with the left and right surround channels. A pilot signal is used to direct the sound from the side surround channels to the upper surround channels when needed.

Abstract: Matrix reproduction decoding means derive from input signals intended to feed a stereophonic plurality of loudspeakers output signals intended to feed a second greater plurality of loudspeakers in a stereophonic arrangement covering a sector of directions, substantially so as to preserve total reproduced energy to within an overall gain and equalization, and to preserve to within constants of proportionality the angular dispositions of reproduced acoustical velocity and sound intensity vectors at an ideal listening position. Preferably for two-channel signals matrix means is frequency-dependent giving increased angular width above 5 kHz, and may incorporate width control. Matrix means encoding loudspeaker feed signals into transmission channel signals, and matrix means decoding transmission channel signals into loudspeaker feed signals may be used giving overall matrix means in accordance with the invention.

Abstract: In an MPEG multi-channel audio signal processor, a decoder requires a respective decoder matrix for determining different output channels from coded audio data. Some transmitted information indicates basic parameters of the multi-channel system. This information may be used to address a currently required decoder matrix which is stored in a decoder memory. The storage of a large number of such matrices would be required to enable the decoder to decode all possible channel configurations. Instead of addressing a required decoder matrix stored in decoder memory, initially the current encoder matrix is reconstructed in the decoder using the related transmitted information. The required decoder matrix is then computed from the reconstructed encoder matrix using a matrix inversion technique.

Abstract: A device for effecting a modification in a stream of transmission blocks detects a transmission block to be modified and generates a detection signal via detection means, which comprises delay means for effecting a delay in the stream of transmission blocks. The device further comprises memory means for generating, in response to the detection signal, the modification to be applied, and combining means for combining the stream of transmission blocks and the modification to be applied, provided with a first input for receiving the stream of transmission blocks, with a second input for receiving the modification to be applied and with an output for generating a modified stream of transmission blocks. The combining means comprises switch-over means for coupling one of the inputs through to the output, as a function of the detection signal. Due to the use of the switch-over means and due to the delay means being a part of the detection means, the combining means can be bufferless.

Abstract: Spectral imbalance (alteration in timbre) when playing home video versions of motion pictures having soundtrack equalized for playback in a room whose room-loudspeaker system is aligned to the standard motion picture theater X-curve is overcome by timbre correction which compensates for the X-curve equalization. Surround-sound home playback of motion pictures is enhanced by employing main channel loudspeakers that produce generally direct sound fields and surround channel loudspeakers that produce generally diffuse sound fields. In addition, the reproduced surround-sound channel is further enhanced by decreasing the interaural cross-correlation of the surround-sound channel sound field and by reducing comb filtering effects in the surround-sound channel at listening positions within the room, preferably by introducing slight pitch shifting in the signals applied to multiple surround loudspeakers.

Abstract: Spectral imbalance (alteration in timbre) when playing home video versions of motion pictures is overcome by re-equalization according to a unique correction response curve which compensates for the equalization for playback in large theater-sized auditoriums inherent in motion picture soundtracks. Surround-sound home playback of motion pictures is enhanced by employing main channel loudspeakers that produce generally direct sound fields and surround channel loudspeakers that produce gnerally diffuse sound fields. In addition, the reproduced surround-sound channel is further enhanced by decreasing the interaural cross-correlation of the surround-sound channel sound field and by reducing comb filtering effects in the surround-sound channel at listening positions within the room, preferably by introducing slight pitch shifting in the signals applied to multiple surround loudspeakers.

Abstract: A television receiver includes a volume control circuit (4) for controlling levels of sound signals corresponding to a left channel, a right channel, a center channel and a surround channel and speakers (6 to 10) corresponding to these channels. The television receiver further comprises a test tone circuit (11; 18), a microcomputer (14) and a character display circuit (16). The test tone circuit (11; 18) supplies a test tone of a prescribed frequency sequentially to the speakers (6 to 10) through the volume control circuit (4). The microcomputer (14) provides a command to the character display circuit (16) so that a CRT 17) displays which speaker is currently supplied with the test tone as well as volume levels of the respective speakers.

Abstract: The present invention provides a multi-channel stereo reproducing apparatus which can reproduce a recording medium such as an audio disc or the like in which in order that users can enjoy screen musics or the like reproduced at, for example, a concert hall and a movie theater.

Abstract: A directional enhancement system for quadrophonic sound systems wherein the improvement comprises an automatic dimension control. The automatic dimension control utilizes a plurality of limiting devices, each of which has an input terminal, an output terminal and a control terminal and is operative to limit the voltage at its output terminal to the lesser of the voltages appearing at its input terminal and its control terminal. The dimension control can also be operative to limit the maximum values of the directional control signals generated and their sums to a voltage controlled by the user of the system thereby limiting the amount of directional enhancement provided by the system.

Abstract: The disclosed invention relates to directional enhancement systems and provides apparatus for enhancing the directional content of information contained in a plurality of composite signals derived from preceding decoding apparatus of the system. The apparatus of this invention includes a plurality of limiting devices equal in number to the number of control signals provided in the processor of the directional enhancement system. Each one of the plurality of limiting devices has an input terminal connected to a different one of the control signal outputs of the processor, a control terminal and a control device having an input coupled to a variable control voltage source and an output coupled in common to all of the control terminals of said limiting device. The apparatus of this invention limits any control signal which may be developed in the processor to a value less than or equal to that which would obtain in the absence of the dimension control apparatus of this invention.