Showing papers on "Audio signal processing published in 1985"

Fast Algorithms for Digital Signal Processing

Abstract: Fast algorithms for digital signal processing , Fast algorithms for digital signal processing , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

Stereo laser disc viewing system

Abstract: A portable television playback system includes a video source unit, video processing circuitry, audio processing circuitry, and a stereo viewing and sound unit. The video source unit is a television receiver, a small videocassette tape cartridge player, or a stereo optical video disc player. The viewing and sound unit has stereoscopic and stereophonic capabilities and is generally a head worn unit having right and left image display devices and right and left earphones. The video and audio processing circuits receive the signals from the video source unit and parallel the video and audio signals to drive the stereo output devices if the source is a television receiver or a videocassette tape player or perform demultiplexing functions to separate the right and left video and audio signals from the right and left multiplexed video/audio signals. The video source unit and the video and audio processing circuits are packaged in a single portable case which may be connected to the head worn viewing and sound unit by an appropriate cable for use.

Video/audio coded data recovery from a record medium

Abstract: Method and apparatus for playing back a plurality of digitally encoded audio messages along with associated video data. The audio messages are combined along with a plurality of corresponding audio message start address signals when recorded on a recording medium. The digitally encoded information can be recorded in the audio domain, i.e. as digitized audio recorded on an audio channel of the medium, or in the video domain, i.e., as digitized audio recorded on the video channel of the medium. In playback, the address and audio data signals are retrieved from the recording medium and stored. The address signals are utilized to access selectable messages for decoding and playback of the selected audio message.

Apparatus and methods for electrical signal discrimination

Abstract: A novel apparatus and method for electronically determining whether audio signals which are present in an electrical audio device (for example, a telephone) are voice signals or, on the other hand, some type of supervisory or system-generated signals. Audio signal lines are connected to an audio detector and a digitizer. The audio detector provides an output which indicates the presence of an audio signal. The digitizer transforms any audio signal into a series of high and low level signals in some manner. The outputs from the audio detector and the digitizer are then provided to a central processing unit which is used to analyze the data. If an audio signal is detected and the digitized audio signal is determined to have a regular periodic pattern, it is presumed that the audio signal is some type of system-generated supervisory tone. If, on the other hand, the digitized audio signal does not have a regular periodic pattern, it is presumed that the audio signal is a voice signal. Accordingly, upon detecting an irregular audio signal, the central processing unit produces an output signal which can be detected by associated circuitry as indicating that voice signals are present.

Audio processing system for restoring bass frequencies

Abstract: An audio processing system for injecting left and right channel audio signals with a signal having a fundamental frequency component that is half the frequency of the highest amplitude low frequency component in the left and right channel audio signals. The left and right channel audio signals are combined to form a monaural signal that is low pass filtered and applied to a demodulator circuit. The demodulator circuit generates a control signal having a frequency that is half the frequency of the highest amplitude frequency component in the signal at the output of the band pass filter. The control signal varies the phase of the signal at the output of the band pass filter according to the polarity of the control signal. The resulting signal is selectively added to the left and right input signals. In order to prevent the audio processing circuit from producing annoying artifact when the audio signals are vocally generated, a voice detector determines that the input signals are from a vocal source and then disables the audio processing circuit. The voice detector operates by comparing the monaural (left plus right) signal to a differential signal (left minus right). Vocal source material has a relatively higher monaural signal while a musical source has a relatively higher differential signal.

Digital graphic equalizer

Abstract: A digital graphic equalizer includes a pulse-sequence generator for generating a sequence of pulse signals, a first digital signal processor for filtering the pulse signals to produce a filtered signal, a digital-to-analog converter responsive to the filtered signal for producing a calibrating signal, and a loudspeaker responsive to the calibrating signal for propagating a calibrating sound in a listening environment, the frequency characteristics of the calibrating sound being subject to modification by the listening environment. A detector detects the calibrating sound as propagated in the listening environment and produces a detection signal representative thereof. An analog-to-digital converter is responsive to the detection signal for producing a digital signal corresponding thereto, and a second digital signal processor is responsive to the digital signal for producing a plurality of frequency-divided signals. A spectrum analyzer is responsive to the frequency-divided signals for analyzing the frequency characteristics of the calibrating sound as propagated in the listening environment and producing a compensating signal adapted to compensate for the modification by the listening environment of the frequency characteristics of the calibrating sound.

Digital audio synchronizing system with cross-fade means

Abstract: A digital audio synchronizing system resynchronizes the audio signal of a video signal by storing the audio signal in a memory and reading it out from the memory after a time period which is related to the time by which the video signal is delayed as a result of being synchronized to a reference video signal. In order to prevent a discontinuity in the audio signal waveform caused by variations in the time difference between the video signal and the reference signal, the digital audio signal is read out from memory addresses which correspond to the previous difference time and also to a new updated difference time value. The two outputs which are generated by reading the signal from two different areas of the memory are cross-faded with one another over a predetermined time period. The cross-fade operation can be repeated over several cycles, each taking a predetermined unit of time until the audio signal is synchronized to its video counterpart.

Television sound signal processing apparatus

Abstract: A television sound signal processing apparatus receives a digitized delta-encoded sound signal being superposed in the horizontal blanking period and a digital signal showing the standard value of said sound signal being superposed in the vertical blanking period, compares the reference signal of this field with that of one field before, and, when the difference is greater than specified, employs the decoded value of the delta encoded signal immediately before that reference signal as the standard value for delta decoding of sound signal. The apparatus is intended for use in the sound transmission of a CATV system, a pay TV system or the like.

Apparatus for recording and reproducing video signal and digital signal other than video signal

Abstract: In a recording and reproducing apparatus wherein a video signal and an audio signal are recorded on the same recording track, a signal subjected to a quadrature differential PSK modulation with PCM audio signal is generated as an audio recording signal. The audio recording signal is disposed between occupied bands of FM luminance signal and down converted chrominance signal in a video recording signal and also recorded on a track where the video recording signal is to be recorded.

Analog to digital conversion method and system with the introduction and later removal of dither

Abstract: For the distortionless conversion of an audio or like data signal from analog to digital form as by pulse code modulation, the input data signal is time division multiplexed with an analog dither (white noise) signal to provide a multiplex signal composed of the analog dither signal and an analog data/dither signal, the latter being an addition of the analog data and dither signals. Then the multiplex signal is converted from analog to digital form by one and the same analog to digital converter. The subsequent removal of the digital dither component from the digital data/dither signal provides a digital data signal as a replica of the input analog data signal. The use of the same converter for the conversion of both dither signal and data/dither signal from analog to digital form makes possible the maximum possible removal of the dither from the digital data/dither signal.

Recording and reproducing digital audio signals formed into groups of varying lengths

Abstract: A method of recording a digital audio signal in association with a digital video signal which is to be recorded in oblique tracks on a magnetic tape using a rotary head the rotational frequency of which is locked to the digital video signal, comprises the steps of assembling incoming audio data words which correspond to successive samples of an audio signal into groups nominally of N audio data words where N is the number of audio samples corresponding to the digital video signal to be recorded in one oblique track, allowing the number of audio data words in each group to vary preferably over the range N-1 to N+1 to maintain synchronism of the audio signal with the rotational frequency of the rotary head, coding the audio data words into error-correcting blocks for recording by the rotary head, and associating with each error-correcting block a status code for use on reproduction and which indicates whether the number of audio data words in the corresponding group is N-1, or N+1.

Automatic gain and frequency characteristic control unit in audio device

Abstract: An automatic gain control unit particularly adapted for vehicular use is disclosed. the ambient noise level inside the vehicle is detected (3-5), as is the level of the audio signal (3-2). A difference is formed (3-3) between detection signals thus produced, and a frequency characteristic of a gain varying device (3-1), inserted in an audio signal path of the audio device, is varied according to this difference.

Remote control equipment for use with an audio system

Abstract: A remote control handset for use with an audio system in which the audio system includes a tuner, a compact disk player an amplifier, speakers, etc. The handset also includes a display for displaying the information contents of the control signals. A cassette recorder also incorporated in the handset produces an output signal which is modulated on a special carrier and transmitted over a signal path to an antenna coupled to the tuner of the audio system in order to reproduce the recorded signals.

Method and apparatus evaluating auditory distortions of an audio system

Abstract: Method and apparatus for evaluating the auditory distortion of an audio system, wherein an audio signal, whose auditory distortions are to be evaluated, is filtered by a notch filter to remove its fundamental frequency, and is then fed through a primary weighting network comprising three high pass filters followed by a secondary weighting network. The filtered, weighted signal is then amplified, recitified, further filtered, compared by taking the ratio with the magnitude of original signal and finally fed to a display unit to sow a figure that represents auditory distortion characteristics consistent with what is actually perceived by human auditory faculties.

Programmable multifrequency digital tone receiver

Abstract: A circuit arrangement for filtering input signals carried on PCM channels. The circuit arrangement includes a plurality of digital signal processors arranged in a parallel manner each having a set of filtering operations, a multiplexer for distributing the input signals to each digital signal processor, a processor for analyzing frequency characteristics output by the digital signal processors and an addressing PROM for controlling a correspondence between the PCM channels and the filtering operations in each of the digital signal processors.

Digital Signal Processing in Video Tape Recorders

Abstract: Digital processing was successfully introduced into television sets by our system of VLSI circuits. It is the next logical step to replace the even more complicated analog processing in Video Tape Recorders (VTRs) of the well known systems (VHS, Beta, Video 2000) by digital means.

Digital tone squelch detector

Abstract: A digital tone squelch detect circuit functions to give an enabling signal for audio transmission in an FM radio network. The circuit comprises an analog to digital converter which outputs a binary coded signal representative of the voltage level of a received audio tone signal. The binary signal is then placed into a shift register which periodically is rotated and multiplied by a reference clock signal for correlation with a stored replica of the tone. The output of the correlator, which is representative of the degree of correlation, is fed to an accumulator which integrates it and sends it to a comparator where its binary valve is compared to an arbitrary threshold binary value by a hysteresis network. After detection the hysteresis established circuit outputs a tone detect signal and lowers the detection threshold so as to maintain the tone detect signal during periods of signal fadeout. However, if no signal is detected for several cycles, the threshold is raised to the previous binary level so as to avoid triggering on noise.

Electrical signal discrimination

Abstract: The electrical response of a transducer contains a data-providing signal or signals superimposed on an unwanted time-variable background signal which is independent of the data-providing signal or signals. A system processing the transducer response utilizes an electronically stored digital simulation of the background components whereby combination of the transducer output with the digital simulation, after digital to analogue conversion of the latter, substantially frees the transducer output of the background component to facilitate detection of the data-providing signals.

Rotary head digital audio tape recorder with multiple recording modes

Abstract: This invention relates to an information signal recording apparatus which can be used also as an audio tape recorder only. When it is used only as the audio tape recorder, an audio signal is sampled with a frequency m times the sampling frequency of an audio signal which is used upon recording a video signal and the thus sampled PCM digital audio signal is diffusively recorded on at least two recording intervals thereby to improve the tone quality of the audio signal and the compatibility with the audio tape recorder using a video tape recorder of the same kind can be established.

Audio signal generating apparatus for generating an audio signal to be recorded on a video disc

Abstract: An audio signal generating apparatus generates an audio signal which is to be recorded on a video disc so that the audio signal is normally reproduceable in a normal reproduction mode, where the video disc is recorded with a first composite video signal or a second composite video signal so that the first composite video signal related to the same field or the second composite video signal related to the same picture frame of a movie film is repeatedly recorded for a plurality of fields in each track turn and a picture is obtained from the video disc in the normal reproduction mode as a pickup reproducing element scans along a scanning locus including a forced track shift. The audio signal generating apparatus produces a time base expanded audio signal which is expanded of the time base by M (M is a rational number greater than one) by reproducing a pre-recorded audio signal from a first recording medium which is pre-recorded with an audio signal separated from a television signal at a speed which is slower than a speed at the time of recording the first recording medium, and compresses the time base of the time base expanded audio signal by 1/M based on clock signals which are in phase synchronism with a periodic signal in the first or second composite video signal so as to produce a time base compressed audio signal having portions of information repeated. This time base compressed audio signal is recorded on a second recording medium together with the first or second composite video signal related to the same field or the same picture frame for every aforementioned plurality of fields.

Digital signal processing system and method

Abstract: A digital signal processing system monitors variation of the signal level of a reproduced signal and also monitors variation of the differentiated signal level. The system generates a read-enable pulse when the reproduced signal level rises or drops across a predetermined threshold level and this is followed by a zero-crossing in the differentiated signal level.

Signal reception system for television receiver

Abstract: A signal receiving system for a TV receiver incorporates at least two independent front end circuits for frequency-converting antenna signals to a lower frequency, with the output signals from these front end circuits being utilized separately to derive the video and audio signal components of the TV signal. Independent control of AGC applied to the audio and video signal components respectively can thereby be implemented, or, in the case of diversity reception using two or more antennas, the optimum antenna for reception of the video and audio signal components respectively can be selected in a mutually independent manner, to thereby attain substantially improved diversity reception, e.g. for a TV installation in a moving vehicle.

Video color transmission system with dual audio channels

Abstract: A video system in which the end portion of a conventional TV picture waveform, normally partially unoccupied by picture information, is encoded with a monaural audio channel which supplements the conventional TV audio channel. A transmitter includes means for encoding the audio channel with conventional video red, green and blue signals, while a receiver decodes the video signals to reconstruct the supplemental audio channel.

Apparatus for magnetically recording and/or reproducing two-channel audio signals together with a color video signal in successive oblique tracks on a magnetic tape

Abstract: In an apparatus for magnetically recording and/or reproducing two-channel audio signals and a color video signal, the color video signal is processed to provide a frequency-modulated luminance signal and a frequency-converted chrominance signal in a band below that of the frequency modulated luminance signal, and the two-channel audio signals are processed to provide a frequency-modulated audio signal including alternated first and second segments respectively corresponding to the two-channel audio signals. The frequency-modulated audio signal is mixed with, and located between the frequency bands of the frequency-modulated luminance signal and the frequency-converted chrominance signal to provide a mixed signal which is recorded in successive oblique tracks on a magnetic tape. In the reproducing mode, the luminance and chrominance signals are obtained from the frequency-modulated luminance and frequency-converted chrominance signals in the mixed signal reproduced from the magnetic tape, and the frequency-modulated audio signal obtained from the mixed signal is demodulated to alternately provide the first and second segments which are separated from each other for producing the two-channel audio signals, respectively.

Information reproducing device with dynamic drop-out compensation inhibiting means

Abstract: An information reproducing device for reproducing a computer program digital data information contained in audio band signals of a video disk and capable of preventing phase disturbance of the digital data information and deterioration of the data reading capacity. The device comprises detecting means for detecting presence of the digital data information including binary signals contained in reproduced audio band signals, and control means for controlling operations of a drop-out compensating circuit in an audio signal reproducing circuit in response to an output of the detecting means when the presence of such digital data information is detected by the detecting means.