Showing papers on "Audio signal processing published in 1979"

System for transmitting data simultaneously with audio

Abstract: An FM broadcasting system is disclosed for transmitting a data signal simultaneously with an auxiliary audio program on the same subcarriers of an FM transmission channel. The main program is transmitted on the FM transmission channel carrier and the auxiliary audio program, which may be background music, is transmitted on the subcarriers in a conventional manner. According to the present invention, the data signal, which is added to the auxiliary audio program, is a binary digital information signal. This binary digital information signal is used to generate a signal which modulates the phase and amplitude of a data reference signal. The resulting phase transition of the modulated data reference signal represents the binary value of the binary digital information signal. The amplitude of the modulated data reference signal then is adjusted in an automatic gain control amplifier relative to the amplitude of a corresponding frequency range of the auxiliary audio program. This amplitude adjusted signal is combined in a linear summing network with the auxiliary audio program and transmitted over the FM transmission channel. The receiver is capable of receiving one or more of the main program, the auxiliary audio program and the data signal.

Method and equalization of home audio systems

Abstract: A method is provided for correcting errors in the overall reproduction characteristics of an audio system installed in a residence. The method may include the steps of generating a test signal as an input to the audio system and converting the resulting sound generated by the system and its room environment into stored data whose values are a function of the sound. This data is then transported from the residence of a processing center. At the processing center, the stored data is read and utilized to fix the characteristics of an equalizer such that when it is installed in an audio system, it will give the desired correction to the output thereof. Thereafter, the resulting equalizer is transported to the residence and installed in the audio system.

Subscriber-limited reception television broadcast security encoder-decoder system

Abstract: A method and apparatus for encoding and decoding of standard television signals are provided for enabling reception thereof in an intelligible manner only by authorized subscribers. The scrambling of the video signals is effected by inversion of the video signals of some horizontal scan lines on a pseudo-random basis to produce a picture having some video signals inverted and others not inverted which is unpleasant to view and virtually unintelligible. The scrambling of the audio signals is effected by conversion of analog audio signals to coded digital audio signals. A plurality of unique pulse coded control signals consisting of 32-bit binary pulse trains are transmitted separately to identify individual authorized subscribers and to provide information needed to unscramble the scrambled video and audio signals. When there is a comparison between one of the pulse-coded control signals and a unique address code stored at a particular subscriber's receiver, unscrambling of the video and audio signals occurs in the same sequence as used for scrambling so as to provide restored video and audio signals without degradation in picture and sound qualities.

Audio-digital processing system for demultiplexing stereophonic/quadriphonic input audio signals into 4-to-72 output audio signals

Abstract: An audio-digital processing system for processing and converting audio localization data from stereophonic or quadriphonic input audio signals into digital localization data. Said digital localization data is further processed into digital commutation data which demultiplexes said stereophonic or quadriphonic input audio signals into 4 . . . 16 . . . 72 output audio signals. This system includes an Input Audio Processor and a Psychoacoustic Data Converter that process and convert each audio field of audio localization data into digital localization data, comprising: digital phase-angle differential, phasor differential, and amplitude differential data; digital field activity, threshold, and dropout data; and digital peak-amplitude strobes. Each type of digital localization data is updated in a corresponding memory for each change in the associated audio localization data. Each corresponding memory is enabled, inhibited, or cleared by respective digital threshold and/or dropout data which are responsive to predetermined audio signal-to-noise amplitude relationships. This system also includes a Psychoacoustic Data Processor that processes each type of updated digital localization data into digital commutation data (a digital psychoacoustic process analogous to binaural fusion). This digital psychoacoustic process functions to: execute and priority evaluate demultiplexing decisions for each output audio field; restore the reproduced sound to near infinite separation; resolve monophonic, stereophonic, and quadriphonic directional ambiguities; and provide preselectable quadrifield operations that create permutations of listening experiences previously unobtainable from the same recording. These preselectable quadrifield operations function to create 16 selectable listening formats that interchange the original panpotted musical instrument/voice positions to other predetermined transducer positions; sequentially reposition, or continuously swirl the discrete sound images in the 360-degree quadrifield; and preselect 4 . . . 16 . . . 72 output audio channels to match the number of transducers configured by the listener. This system further includes an Output Audio Processor that processes said stereophonic or quadriphonic input audio signals into output audio signals. The output audio signals are processed in accordance with the preselectable quadrifield operations into one or more of the following: discrete direct audio signals, a system bass signal that automatically tracks the Fletcher-Munson equal loudness contours, recovered/synthesized concert hall ambience signals, rear matrix encoded audio signals, recovered direct audio signals when rear matrix encoded audio signals predominate, and recovered rear matrix encoded audio signals when discrete direct audio signals predominate. This system includes a Psychoacoustic Audio Demultiplexer that demultiplexes, in response to said digital commutation data, said output audio signals into 4, 5, 6, 8, 10, 12, 14, 16 . . . 72 preselected output audio channels and associated configuration of transducers. The demultiplexed and point-source reproduced discrete sound images establish a 360-degree walkthrough quadrifield that eliminates the stereophonic/qaudriphonic seat; a consumer problem initiated in 1924 and defying practical solution since the first commercial stereophonic tape recording in 1954 or disc recording in 1958.

Digital video and audio file system

Abstract: A digital video and audio file system is provided for use in systems such as a center-to-end video communication system In the file system, video information, such as a color television video signal, is digitized in such a manner that it is separated into a luminance (Y) signal and a carrier chrominance (C) signal and these separated components are processed by the code differential method and the variable length encoding method The digital signal thus digitized is recorded in a digital recorder On the other hand, audio information is digitized by the AD-PCM encoding method and recorded in the same recorder In encoding the video and the audio information, a part of hardware is used in common for both the signals, thus saving the hardware of the file system

Digital radio transmission system

Abstract: A digital radio transmission system for compensating for co-channel or adjacent channel interference or signal level variations and distortions is provided. The system includes apparatus for transmitting a digital signal having a first signal level from a first location to a second remote location, apparatus for monitoring at the second remote location the bit error rate of the received digital signal and apparatus for changing the level of the transmitted digital signal when the received bit error rate is different from a predetermined value.

Scrambling system for television sound signals

Abstract: An audio scrambler operates on segments of audio divided from a continuous audio signal to rotate head-to-tail the string of information contained in the segment by an amount which is at pseudo-random between the successive segments. When the segments are compressed to video format, the scrambled compressed audio signals are inserted into an unused line of the vertical blanking space of a television system for transmission with the video signals. The inserted audio is combined with decoy signals, also in the vertical blanking space to increase security of transmission. Concurrent scrambling of compressed audio signals and video signals is provided.

Apparatus for producing a plurality of audio sound effects

Abstract: Apparatus for producing a plurality of audio sound effects such as shots, explosions, and airplane and car sounds, used in electronic games utilizes a variable clock driving a variable digital noise generator whose audio output amplitude is shaped by either of two types of control units. In one type the density or duty cycle is varied by selectively ANDing together outputs from a polynomial counter. In a second embodiment a digital to analog converter utilizing gated resistive summing provides the amplitude control the gates being driven by a four bit data register which in turn is driven by the game control means.

Method and apparatus for editing digitally recorded audio signals

Abstract: An apparatus for editing digitally recorded audio signals in which entry and exit edit points are designated based on a display of data derived from audio signal data proximate to the edit points. The apparatus enables the automatic selection and combination of portions of audio signals on at last two channels to produce a composite audio signal digitally recorded on a record medium.

Simulcast transmission system

Abstract: A simulcast transmission system is disclosed. The system comprises a master station including means for generating and transmitting over a medium an audio signal containing a message signal and a pilot frequency signal inserted into the audio signal band, and at least two slave stations adapted to receive the audio signal transmitted over the medium and including a radio frequency generator of the phase locked loop type and means for isolating the pilot frequency signal from the audio signal and for synchronizing the frequency of the radio frequency generator with such pilot frequency signal.

Analog to digital converter using timed level changes

Abstract: An analog signal is sampled in response to a sampling command. Each time that the analog signal, or the difference between the analog signal and the previous sample thereof, crosses a respective reference level, a digital signal is produced. Each digital signal consists of a code representing the level crossing or incremental change in level which has occurred and a count representing the time which has elapsed since the last sample command. A digital signal is also produced if the elapsed time reaches a predetermined period. On production of each digital signal, a sampling command is produced and the elapsed time counting is recommenced. The digital signals constitute a digital representation of the analog signal. The converter is particularly useful for converting analog signals having both very high and very low frequency portions, such as current surges which occur on telephone lines affected by lightning (high frequency) and 60 Hz induction (low frequency).

Solid state digital audio scrambler system for teletransmission of audio intelligence through a television system

Abstract: An audio scrambler digitally samples a continuous audio signal, scrambles the derived samples and inserts at least one scrambled sample in the unoccupied region of the video signals of a video system for transmission line per line as an analog composite audio-video signal. A RAM device is used for this purpose which has the digital samples stored sequentially, then read at random. A special memory arrangement is used as a scratchpad in order to insure that while addressing the RAM at random there will be no repetition, nor omission of a particular address. Provision is made for the insertion of more than one sample per video line, in particular while transmitting severe audio signals on the same video system. The same technique is used at the receiver end for unscrambling the samples once extracted from the video lines.

Digital audio signal recorder

Abstract: A digital audio signal recorder for obtaining coded signals having a first check code generator for generating the sum of module 2 for each bit of pieces of predetermined sampled data; and further has a circuit operatively coupled to said generator for arranging the sampled data, a first check code and a second check code at positions spaced on a time axis from each other. This invention also provides a method of generating such a digital audio signal. This invention is advantageous because it makes possible a low rate of redundancy and a simple decode circuit.

Minimum space digital storage of analog information

Abstract: Analog or digital information, for example an audio input, is converted to a digital representation and encoded prior to storage in a digital form for minimizing the space required for storage of the digital information. Pauses are eliminated and encoded in a form indicating the occurrence of the pauses. Data is compared with prior received data such as to detect repetition. When repetition is detected, a code indication of the period of repetition and the duration of repetition is inserted in the stored data. Information is restored utilizing decoding networks responsive to the inserted codes which cause reinsertion of the pauses and repetitions. Also, when the information is restored, background audio may be provided in the silent periods either from a separate memory or, when available, from an audio input circuit.

Method and system of controlling sound and effects devices by a film strip

Abstract: A method and system of blending the effective audio sensation in a theater having a plurality of audio speakers driven by a single program signal recorded on a motion picture film strip as the film strip is being projected in the theater, which method and system includes the driving of each of the speakers in the theater with a common program signal through an amplifier having a gain controlled by an analog electrical signal whereby the level of the analog signal determines the volume of the program signal at each of the speakers and creating a digital gain control signal for each of the speakers in response to a control signal recorded periodically on the film strip at locations on the film strip determined by the desired volume of a given speaker at a given time which digital gain control signal is converted to an analog signal and is used for controlling the driving amplifiers of each of the speakers in the theater in which the film is being projected.

Pager with escalating audio alert signal level

Abstract: An alerting device, such as a radio pager, which produces an audible alerting signal includes a signal level control which causes the alerting signal to be initially produced at a low audio level, with the signal increasing or escalating to a higher audio level. The signal level can increase continuously in a smooth rise, or can increase in steps. The level control can include an attenuator which initially reduces the signal level, to which a control signal is applied to reduce the attenuation and increase the alerting signal. The attenuator can be coupled to an audio amplifier so that the overall gain of the signal applied to the transducer producing the audible signal is increased from an initial low signal level as the signal continues.

Monitor system for a digital signal

Abstract: A monitor system comprising: an adder for summing up a plurality of unknown analog electric quantity signals denoting the operating conditions of such as a transmission line; a multiplexer for generating output signals corresponding to the plural analog electric quantity signals and also to a signal denoting the result of addition made by said adder; an A-D converter for converting output analog signals from the multiplexer into digital signals; and a monitor which sums up those of the output digital signals from the A-D converter which correspond to said plural analog electric quantity signals, compares a signal denoting the result of said addition with a digital signal converted from an output signal from the adder, receives an error detection signal denoting the known prescribed electric quantity converted into a digital signal through the multiplexer and A-D converter, and judges the operating condition of the A-D converter from the contents of said received digital signal.

Aircraft simulator digital audio system

Abstract: A method and apparatus for providing mass storage of vocal information by means of a digital communication system for use with a training simulator is disclosed. Unlike prior art analog records and playback systems, such as tapes, etc., the inherent advantages and flexibility available with respect to a digital system including randomly accessible voice messages, convenience of editing the stored data, and management and control by the computational system of the training simulator are available with the present invention. In general, the system of this invention comprises an input device, such as a microphone (30), an encoder (54) for encoding the analog information from the microphone (32) to digital format, a digital processing controller or computer (20) for processing the digital communication data in response to a stored program such that it is suitable for use with the computational system, and a mass storage media (38) for storing the processed digital data. To provide audio response and playback from the stored digital data, the system includes a processor (36) for selectively reading stored bulk data and processing the selected data into a form suitable for decoding, a decoding means (66) for translating the digital data to analog information, and an output device (42) for providing an audio or vocal output to a listener.

Universal analog and digital tester

Abstract: Method and apparatus for comparison-type testing of electronic devices which generate analog waveform output signals. A reference unit output signal and an output signal of a unit under test are paired and selectively and synchronously compared in response to a common input signal. The comparison is performed by means of subtraction producing an error signal, which error signal is compared against a limit window. The limit window may have fixed or preferably programmable amplitude limits whereby a digital decision signal is generated whenever the limits are exceeded.

Use of High-Speed Microprocessors for Digital Synthesis

Abstract: This paper describes a processor specialized for the synthesis and treatment of sound signals, realized with bipolar bit -slice microprocessors. This processor has been studied at the Musical Department of I.N.A., within a project aiming at the development of digital systems for sound processing with real-time control (SYTER Project). A prototype has been built with the help of Denis Valette. The main characteristic of this processor is that it is completely programmable, which makes it possible to use many existing methods of synthesis or to adapt it to new methods, without modifying the hardware. Three other points have also been crucial for the conception of the processor:

Digital amplitude control for digital audio signal

Abstract: A digital amplitude control apparatus for a digital audio signal in which the output voltage of a linear-type potentiometer or attenuator connected across a DC power supply is converted into a digital signal by an A/D converter, the output voltage being linearly related to the manipulated variable of the slider of the potentiometer, the digital signal is applied as an address signal to a memory which stores in memory locations thereof a series of amplitude control digital values with a desired amplitude changing characteristic, thereby reading out of an accessed location a amplitude control value corresponding to the attenuation set by the potentiometer, and a digitized audio information signal to be amplitude-controlled is multiplied by the amplitude control value read out of the memory by means of a digital multiplier.

Digital encoding of speech and audio signals based on the perceptual requirements of the auditory system

Abstract: : The development of a digital encoding system for speech and audio signals is described. The system is designed to exploit the limited detection ability of the auditory system. Existing digital encoders are examined. Relevant psychoacoustic experiments are reviewed. Where the literature is lacking, a simple masking experiment is performed and the results reported. The design of the encoding system and specifications of system parameters are then developed from the perceptual requirements and digital signal processing techniques. The encoder is a multi-channel system, each channel approximately of critical bandwidth. The input signal is filtered via the quadrature mirror filter technique. An extensive development of this technique is presented. Channels are quantized with an adaptive PCM scheme. The encoder is evaluated for speech and audio signal inputs. For 4.1-kHz bandwidth speech, the differential threshold of encoding degradation occurs at a bit rate of 34.4 kbps. At 16 kbps, the encoder produces toll-quality speech output. Audio signals of 15-kHz bandwidth can be encoded at 123.8 kbps without audible degradation.

Electronic voice detector

Abstract: A voice detector for supplying a control signal in an automatic telephone answering apparatus in response to a voice signal received from a telephone line. A first one of two parallel signal channels generates a first digital signal for an incoming signal having a minimum amplitude with a minimum duration. The second signal channel generates a second digital signal for an incoming signal having a minimum number of consecutive cycles with periods within a predetermined range corresponding to the frequency range of a ringing signal. A logic element combines the first and second digital signals to produce the control signal if simultaneously the first digital signal is present and the second digital signal is absent. Thereby, the control signal is produced only in response to an incoming voice signal, but not in response to a ringing or a noise signal.

Gray scale sync video processing system

Abstract: The blacker-than-black sync pulse of a standard video signal is replaced by a gray scale sync to increase picture signal, permit audio multiplexing and allow security phase inversion by means of encoder and decoder circuitry including a sync stripper, gate and timing generator, audio processor, phase code generator, color reference regenerator, blank and summing amplifier, and phase reversal amplifier.