Abstract: A frame type for a current SBR frame is determined according to a type of end border of a previous frame, as well as presence of a transient in the current SBR frame. A start border is determined according to the end border of the previous SBR frame. For a FIXFIX frame, a low time-resolution setting is used. For a FIXVAR or a VARVAR frame, a search for intermediate borders is conducted in the region between the transient and maximum allowed end border location. The end border is also determined at this stage. If there is excess capacity for more borders, another search is conducted in the region between the transient and the start border. For a VARFIX frame, only one search needs to be conducted, in the whole region partitioned by a variable start border and a fixed end border. All of the above are accomplished with two Forward Search operations and one Backward Search operation.

Abstract: A method of encoding a multichannel signal, such as a stereophonic audio signal, including at least first and second signal components includes transforming at least the first and second signal components by a predetermined transformation into a principal signal including most of the signal energy and at least one residual signal including less energy than the principal signal. The predetermined transformation is parameterized by at least one transformation parameter. The method further includes representing the multichannel signal at least by the principal signal and the transformation parameter.

Abstract: Apparatus and method for transmitting and reproducing stereophonic audio signals are disclosed. The method comprises splitting first and second channels into two frequency bands, combining the lower frequency band signals of the two channels, and transmitting the combined signals of the two channels or signals representative thereof. The apparatus comprises: a splitter for splitting each of the two channels into two frequency bands, a combiner, for combining the lower frequency band signals of the two channels, and a transmitter for transmitting the combined signals, or signals representative thereof, and the higher frequency band signals of the two channels, or signals representative thereof.

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 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 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: 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: A decoding method, medium, and system decoding an input compressed multi-channel signal, as a mono or stereo signal, into 2-channel binaural signals. Channel signals making up the multi-channel signals may be reconstructed from the input compressed signal in the quadrature mirror filter (QMF) domain, and head related transfer functions (HRTFs) for localizing channel signals in the frequency domain, represented as values in the time domain, may be transformed into spatial parameters in the QMF domain. Accordingly, channel signals may be localized in the QMF domain in directions corresponding to the channels, thereby decoding the input compressed signal as 2-channel binaural signals.

Abstract: A method and system accept left and right channel inputs of audio data and provide output audio data for at least three channels in a fashion that may effect a facsimile of the original soundstage on which the left and right inputs were recorded.

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: A method and apparatus for performing audio post processing using mode information that indicates the degree of similarity between a right channel signal and a left channel signal in MPEG-1 layer 3 audio data, are provided. If the difference between the two channel signals is small, a first mode is used in which the high frequency component of only one channel is recovered and the recovered high frequency component is used to recover the high frequency component of the other channel. If the difference between the two channel signals is large, a second mode is selected in which the high frequency component in only one of every two frames is recovered alternately in the left channel and the right channel and the high frequency component of each of the skipped frames is interpolated based on the high frequency components of the previous frame and the next frame.

Abstract: A multi-channel decoder for generating a binaural signal from a downmix signal using upmix rule information on an energy-error introducing upmix rule for calculating a gain factor based on the upmix rule information and characteristics of head related transfer function based filters corresponding to upmix channels. The one or more gain factors are used by a filter processor for filtering the downmix signal so that an energy corrected binaural signal having a left binaural channel and a right binaural channel is obtained.

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 motion picture soundtrack reproduction system has a center front soundtrack channel and a plurality of other soundtrack channels. A volume control adjusts the gain of all the channels. The volume control has a range of settings from a minimum to a maximum, the gain of the center front channel having substantially a first relationship to the volume control settings and the gain of the other channels having substantially a second relationship to the volume control settings, the relationships being such that for a range of volume control settings less than a first setting the gain of the center front channel remains substantially constant while the gain of the other channels decreases as the setting decreases or decreases more gradually than the gain of the other channels as the setting decreases.

Abstract: An information signal reproducing apparatus which is capable of forming a suitable reproducing environment and building an easy-handling reproducing system regardless of differences such as signal format or recorded media of audio data to be reproduced is provided, in which: a medium type of an optical disc and signal format information of audio data to be read from the optical disc and to be reproduced are detected by an RF signal processing circuit and a Video/audio decoding unit so that a system control unit estimates whether the audio data to be reproduced is a music sound, a movie sound or another type of audio data in accordance with the detected information, and, in accordance with this estimation result, the system control unit and an interface control unit control an audio signal processing unit, an audio volume unit and a speaker amplifier unit so as to carry out a signal processing suitable for the audio data to be reproduced.

Abstract: An audio processing unit that provides a high-sound-quality reproduction even when a band property of an input encoded signal drops at or below a Nyquist frequency. The audio processing unit has a band-variable bandpass filter 1500; a band determining section 1700 for determining a passband of the band-variable bandpass filter with respect to a band extension component from an extended band generating section 1300 by using decoding information from a decode-processing section 1100 as a band determination information; and a bandpass filter controller 1600 for controlling the passband of the band-variable bandpass filter in accordance with an indication from the band determining section.

Abstract: A codec in a processor-based system handles at least two separate audio programs at the same time. This may be useful, for example, for simultaneously playing one audio program while recording another audio program. A first digital to analog converter pair may be coupled to a first mixer and a second digital to analog converter pair may include a second mixer. Thus, two separate audio programs may be handled at the same time, each by a separate digital to analog converter and mixer.

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: This invention addresses sound recording and mixing methods for 3-D audio rendering of multiple sound sources over headphones or loudspeaker playback systems. Economical techniques are provided, whereby directional panning and mixing of sounds are performed in a multi-channel encoding format which preserves interaural time difference information and does not contain head-related spectral information. Decoders are provided for converting the multi-channel encoded signal into signals for playback over headphones or various loudspeaker arrangements. These decoders ensure faithful reproduction of directional auditory information at the eardrums of the listener and can be adapted to the number and geometrical layout of the loudspeakers and the individual characteristics of the listener. A particular multi-channel encoding format is disclosed, which, in addition to the above advantages, is associated with a practical microphone technique for producing 3-D audio recordings compliant with the decoders described.

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: Reproduction accuracy of a digital signal, representing for example stereo audio signals, is improved by transmitting sample data which have been encoded to form transmission signals. The transmission signals are arranged in consecutive frames, each frame including a plurality of information packets, and each information packet including N bits. The number of information packets in a frame is determined by the ratio of the product of the transmission bit-rate and the number of samples represented in the frame, to the product of the number of bits in a packet and the sampling frequency. The transmission signals are recorded in a record carrier, or are transmitted in real time. In a digital stereo audio signal embodiment, the samples may be sub-band encoded or transform encoded. The transmission signal may include an indicator signal indicating a combination of certain samples, or scale factor signals for specific components of the sampled signal.

Abstract: A sound processing system reduces the instances when only a center speaker is heard. The gain of a volume setting is adjusted for individual speakers in response to one or more input signals. The gain of the center speaker is attenuated in relation to the global volume setting. In addition or as an alternative, the gain of front and/or rear speakers is increased. A virtual center channel is generated for locations where the center speaker may not be heard.

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: A method for processing and transducing audio signals. An audio system has a first audio signal and a second audio signal that have amplitudes. A method for processing the audio signals includes dividing the first audio signal into a first spectral band signal and a second spectral band signal; scaling the first spectral band signal by a first scaling factor proportional to the amplitude of the second audio signal; and scaling the first spectral band signal by a second scaling factor to create a second signal portion. Other portions of the disclosure include application of the signal processing method to multichannel audio systems, and to audio systems having different combinations of directional loudspeakers, full range loudspeakers, and limited range loudspeakers.

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: The degree of correlation between two audio signals is determined and the channels are normalized according to first and second normalization modes responsive to correlation and uncorrelation respectively.

Abstract: There is provided a surround device which processes stereo signals decoded by a decoder of a multi-channel surround method comprises boost means which boosts middle and low frequency components of a center channel signal in the stereo signals. There is also provided a surround device which processes stereo signals decoded by a decoder of a Dolby Pro Logic method comprises boost means which boosts high frequency components of a surround channel signal in the stereo signals. The boost means is composed of a level detector for detecting an output level of the channel signal, an operation portion for calculating and determining an amount of boost based on a result of the level detector, and a signal boost portion for boosting the channel signal based on a result of the operation portion.

Abstract: The present invention provides a method of decoding two-channel matrix encoded audio to reconstruct multichannel audio that more closely approximates a discrete surround-sound presentation. This is accomplished by subband filtering the two-channel matrix encoded audio, mapping each of the subband signals into an expanded sound field to produce multichannel subband signals, and synthesizing those subband signals to reconstruct multichannel audio. By steering the subbands separately about an expanded sound field, various sounds can be simultaneously positioned about the sound field at different points allowing for more accurate placement and more distinct definition of each sound element.

Abstract: An audio decoding apparatus includes a CPU which groups received sample data into one block. Furthermore, the CPU adds control information relating to attributes to data of each block.

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: An audio decoder solution is here provided where a reduction in computing power is required. The proposed method consists of forcing the multiple output channels to only one type of inverse transformation format. A format of long transform length is more suitable for input signals whose spectrum remains stationary or quasi-stationary. This provides a greater frequency resolution, improved coding performance and a reduction of computing power required. Another format of two or more short transform lengths, possessing greater time resolution, is more desirable for rapidly changing signals with time. The computer power required for two or more short transforms should be higher than for only one transformation. The time versus frequency resolution trade-off should be considered when selecting a transform block length. Advantage is taken of human hearing behaviour to reduce the computing power of a processing engine (e.g. DSP) when downmixing from an M-channel input to a P-channel output is required.

Abstract: Various equivalent adaptive audio matrix arrangements are disclosed, each of which includes a feedback-derived control system that automatically causes the cancellation of undesired matrix crosstalk components in the matrix output. Each adaptive audio matrix arrangement includes a passive matrix that produces a pair of passive matrix signals in response to two input signals. A feedback-derived control system operates on each pair of passive matrix signals, urging the magnitudes of pairs of intermediate signals toward equality. Each control system includes variable gain elements and a feedback and comparison arrangement generating a pair of control signals for controlling the variable gain elements. Additional control signals may be derived from the two pairs of control signals for use in obtaining more than four output signals from the adaptive matrix.

Abstract: An audio reproducing device includes an input for receiving an n-channel input signal, an output for supplying an 1-channel output signal to 1 loudspeakers, and an audio processing unit for processing the input signal. The audio processing unit a signal enhancer for enhancing an m-channel signal part of the n-channel input signal, where m<n, the signal enhancer having, for each channel signal part of said m-channel signal part, a non-linear anti-symmetric monotone transfer function. The audio reproducing device is further provided with a speech-music discriminator, which, in response to one of the channel signal parts of the m-channel signal part designated for speech, generates a control signal indicating the probability p that the one of the channel signal parts contains speech signals. This control signal is used to control the signal enhancer.

Abstract: The invention provides a sound field correction circuit for a surround playback apparatus wherein a decoding circuit is formed from a comparatively simple circuit and similar effects to those of a ordinary sound field correction circuit can be achieved at a reduced cost. A sound field correction circuit includes a decoding circuit for restoring 2-channel stereo signals encoded for a multi-channel surround effect to obtain multi-channel surround signals. The decoding circuit includes an adder for adding the encoded 2-channel stereo signals to each other, a subtractor for subtracting one of the encoded 2-chhanel stereo signals from the other, a level adjusting volume for adjusting the output level of the adder, and another level adjusting volume for adjusting the output level of the subtractor. An output of the level adjusting volume is used as a center channel signal while an output of the level adjusting volume 6 is used as a surround channel signal.

Abstract: In audio-decoder apparatus, a circuit substrate common to a 2-channel model and a 5.1-channel model, on which a decoder and a D/A converter with built-in PLL are installed, and which has installing portions and for enabling installation of D/A converters without built-in PLL. The line connection modes of signal lines connecting the output terminal of the decoder to the input terminals of each D/A converter can be changed by a switching apparatus, corresponding to the channel model, thus it becomes possible to realize D/A converters without built-in PLL having better audio performance under a line connection mode desired for an improved audio performance. Therefore, a good audio performance can be secured, while a common circuit substrate can be used for a variety of channel models, which is advantageous in view of fabrication cost.

Abstract: A system and method of producing an output sound field that is representative of an input sound field compatible with both existing prior art sound reproduction systems, for example ITU 5.1/6.1, and with a three-dimensional reproduction system unique to this disclosure. One embodiment of the disclosed system is comprised of a microphone array, an encoder, a decoder, and a plurality of speakers, some of which may not be located in the plane of the listener. A further embodiment discloses matrices to encode and decode the signals representative of the input and output sound fields respectively.

Abstract: A sound signal encoder for high efficiency encoding of sound signals from a plurality of channels is provided which includes a to-be-correlated object setter (52), to-be-correlated object selector (56) and a variable-length encoder (58). The to-be-correlated object setter (52) sets, on the basis of left-channel frequency information held in a left-channel frequency information holder (50) and right-channel frequency information held in a right-channel frequency information holder (51), index [i] indicating which ones of sine waves on the left channel are to be correlated with, namely, are to be subtracted from, sine waves on the right channel. The to-be-correlated object selector (56) selects a default value read from a storage unit (55) or index [i]-th amplitude information read from a left-channel amplitude information holder (53) as an object to be subtracted from the i-th amplitude information on the right channel according to the index [i].

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: There is provided a surround device which processes stereo signals decoded by a decoder of a multi-channel surround method comprises boost means which boosts middle and low frequency components of a center channel signal in the stereo signals. There is also provided a surround device which processes stereo signals decoded by a decoder of a Dolby Pro Logic method comprises boost means which boosts high frequency components of a surround channel signal in the stereo signals. The boost means is composed of a level detector for detecting an output level of the channel signal, an operation portion for calculating and determining an amount of boost based on a result of the level detector, and a signal boost portion for boosting the channel signal based on a result of the operation portion.

Abstract: In an audio signal encoding apparatus, a first audio signal and a second audio signal are added into an addition-result signal. The first audio signal is subtracted from the second audio signal to generate a subtraction-result signal. A first difference signal is generated which represents a difference in the addition-result signal. A second difference signal is generated which represents a difference in the subtraction-result signal. A plurality of first predictors have different prediction characteristics respectively, and are responsive to the first difference signal for generating first different prediction signals for the first difference signal, respectively. A plurality of first subtracters operate for generating first prediction-error signals representing differences between the first difference signal and the first different prediction signals, respectively. A first minimum prediction-error signal representative of a smallest difference is selected from among the first prediction-error signals.

Abstract: A method of processing a series of input audio signals representing a series of virtual audio sound sources placed at predetermined positions around a listener to produce a reduced set of audio output signals for playback over speaker devices placed around a listener, the method comprising the steps of: (a) for each of the input audio signals and for each of the audio output signals: (i) convolving the input audio signals with an initial head portion of a corresponding impulse response mapping substantially the initial sound and early reflections for an impulse response of a corresponding virtual audio source to a corresponding speaker device so as to form a series of initial responses; (b) for each of the input audio signals and for each of the audio output signals: (i) forming a combined mix from the audio input signals; and (ii) forming a combined convolution tail from the tails of the corresponding impulse responses; (iii) convolving the combined mix with the combined convolution tail to form a combined t

Abstract: A method for decoding an audio signal includes receiving a digital audio signal having a plurality of channels defined thereon, wherein one of the plurality of channels is a center channel and at least one of the other of said plurality of channels is a remaining audio channel; comparing the center channel with the at least one of the other of the plurality of channels to determine a ratio of the center channel to the other of the plurality of channels; and automatically adjusting the center channel and the at least one of the plurality of other channels when a predetermined value for the ratio is not met.

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 digital audio decoder decodes or expands compressed data such as bit stream data, which are compressed based on the MPEG/Audio standard. Inverse quantization circuits perform inverse quantization on plural bit stream data, which are supplied thereto in connection with multiple channels respectively, thus producing inversely quantized data with respect to a prescribed number (e.g., thirty two) of sub-band samples respectively. The inversely quantized data are combined together among the multiple channels with respect to the prescribed number of the sub-band samples respectively. Then, a filter bank synthesizes together combined data corresponding to all of the sub-band samples, thus reproducing original digital audio signals. Multipliers are provided for use in gain control on the inversely quantized data with respect to the sub-band samples respectively.

Abstract: A method of down mixing a plurality of signals including at least a left surround signal, a right surround signal, a left signal and a right signal into a stereophonic pair that is a left transmitted signal and a right transmitted signal includes summing the left surround and right surround signals to provide a monophonic surround signal, filtering the monophonic surround signal to provide a filtered monophonic signal having properties related to the diffraction pattern around the head of a listener, multiplying the filtered monophonic surround signal with a right coefficient signal related to the ratio of the magnitude of the right surround signal to the sum of the magnitudes of the left surround signal and the right surround signal to provide a left product signal and multiplying the filtered monophonic surround signal with a left coefficient signal related to the ratio of the magnitude of the left surround signal to the sum of the magnitudes of the left surround signal and the right surround signal to prov

Abstract: Surround sound encoding and decoding includes apparatus and techniques for encoding a number of major channels of a surround sound signal, such as left, right, center, left surround and right surround, into a lesser number of channels, such as left transmitted and right transmitted, and decoding the lesser number of channels into a larger number of decoded channels, such as left, right, center, left surround and right surround, for being electroacoustically transduced.

Abstract: The invention relates to an audio reproducing apparatus having a converting means for converting main audio signals included in an audio signal for a plurality of channels into audio signals that provide a reproduction sound field similar to that obtained in reproduction by means of speakers even when the audio signals are reproduced by means of headphones; and an adding means for adding an auxiliary audio signal included in the audio signal for a plurality of channels to an audio signal outputted from the converting means; wherein an audio signal outputted from the adding means is supplied to headphones.

Abstract: A apparatus formed on a motherboard of computer complied with PC99 standard for converting to six-channel output from two-channel is disclosed. The apparatus comprises a CODEC, a MIC_IN connector switch, first, second, and third filters, and a resistor circuit. In a six-channel output mode, the rear left and rear right surround signals and LINE_IN_L and LINE_IN_R signals are fed into the third filter.