Abstract: In a video disc mastering system, player control data is conveyed by a block code having framing and field number bits and data for use by a computer external to the player is conveyed by a convolutional code having no framing bits, having error check bits related to a subset of the field number bits conveyed by the player control data and having vertical parity selected to spread data required for predictive and reconstructive error correction over a number of video fields greater than that recorded on one convolution of the disc information track.

Abstract: A digital lowpass filter having controllable gain produces a filtered digital signal by adding to the digital input signal a feedback signal produced from the filtered digital signal. The feedback signal is produced by a delay element and by a gain element including a controllable shifter. The effective gain exhibited by the digital filter can be made to have values between the discrete values produced by the shifter by changing the shifter gain as a function of time.

Abstract: A video disc tracking information encoding system includes a primary encoder for tracking information on a field-by-field basis and a secondary encoder for conveying a subset of the tracking information every N lines within a field. A video disc player for discs recorded with doubly conveyed complete and partial tracking information includes means for recovering the partial tracking information every N lines, comparing it with the complete tracking information recovered during the start of each field and effecting tracking error correction if the partial tracking information differs from a predetermined subset of the complete tracking information thereby facilitating intra-field track error correction so as to enable rapid correction of tracking errors.

Abstract: A digital ratio detector for detecting digitized frequency-modulated (FM) signals develops sum and difference signals from input digital signals and from delayed representations thereof. The sum and difference signals are detected and further sum and difference signals are developed and are applied to respective lowpass digital filters having controllable gain. A gain control circuit develops a gain control signal which is applied to the digital lowpass filters to control the respective gains thereof so that the filtered digital signals produced by one of the digital filters includes digital representations of the deviations of the FM carrier.

Abstract: Digital audio data to be recorded in a pseudo-video format on a disc record is applied to an error check encoder that encodes each line of data with an error check code. The encoder is preset to an initial state corresponding to a recording track number prior to encoding each data line. The track number is changed periodically during recording whereby track information is conveyed by the form of the error check code without requiring additional bits of information in the data lines. Upon playback of the disc, the encoded data is applied to an error check decoder that is preset to an initial state corresponding to an expected track number. Upon decoding, errors in the recovered data are corrected and the recorded track number is recovered. The expected and recovered track numbers are compared to provide a track error correction signal whereby tracking errors may be corrected on a line-by-line basis within each pseudo-video field without need for additional bits in the recorded data.

Abstract: A system for recording and recovering analog signal in digital format utilizes a substantially video field format without the vertical blanking intervals thereby eliminating the need to time compress the information on a field by field basis. The digital signal is encoded for error correction of burst errors at least one line in length. Auxiliary digital information is substituted for particular lines of encoded signal for purposes of identifying the position of the playback transducer. The recovered signal is decoded by an error correcting decoder which recognizes the auxiliary information as a signal burst error and reconstructs the signal that was substituted by the auxiliary information. The decoded signal is then converted to a time continuous analog signal.

Abstract: In a system for recording digital information on a video disc and for playback of the digital information therefrom, the digital data is recorded in synchronism with the color subcarrier signal on a horizontal line adjacent to a constant luminance line. This arrangement facilitates a video disc player having a simple, efficient, video-to-digital interface for separating the prerecorded digital information from the video signal. The player apparatus is responsive to the color subcarrier signal and the chrominance-related output signal of a comb filter, both of which are normally available during video signal processing. Prerecorded digital information representing field number and type of program content is used by a microprocessor controller to provide player features such as locked groove detection, program elapsed time display, and end of program indication.

Abstract: In a signal expander, the envelope of an input signal to be expanded is detected and applied as a control signal to the gain control input of a variable gain device which expands the input signal. The control signal is applied to the variable gain device via an adaptive filter having improved ripple reduction and transient performance characteristics to minimize audibility of gain changes. The adaptive filter includes a low pass filter for producing a smoothed control signal essentially free of ripple and an analog gate for coupling the greater of the smoothed signal or a further signal to the variable gain device, the further signal being equal to the detector output signal less a constant. Compression of an input signal is provided by applying the input signal to the non-inverting input terminal of an amplifier and coupling the (compressed) output signal of the amplifier to its inverting input terminal via the expander.

Abstract: A high performance disc record recording system wherein a digital manifestation of the signal to be recorded modulates a first carrier frequency and a temporally displaced analog manifestation of the same signal modulates a second carrier frequency. The modulated carriers are linearly combined for recording in a single record track. The digital signal is encoded for error detection and/or correction. On playback the modulated carriers are separated and demodulated. One of the separated signals is delayed so that the two signals are returned to temporal coincidence. The digital manifestation of signal is reconverted to analog format and utilized as the primary output signal. However, upon detection of errors in the digital signal the analog manifestation of the signal is substituted for the primary signal.

Abstract: Under certain conditions a video disc player can be responsive to externally applied interference signals to provide a defect in the display of the information recovered from the disc. Apparatus is provided between the pickup circuits and the normal defect compensation apparatus of the player to detect the presence of the external signals and to activate the normal defect compensation apparatus when the external signals are of a relatively high frequency and above a variable offset or threshold level. The threshold is made to vary as a function of the amplitude of the signal provided at the output of the pickup circuits.

Abstract: In a video disc recording and playback system, the video fields on the disc are identified by digital information recorded during the vertical blanking interval. The recorded digital information includes in the order named, a Barker start code sequence, an error detection coset code and information bits which include a field number corresponding to the video field being recorded. The arrangement results in improved noise immunity and simpler decoding hardware in the video disc player. The digital information is utilized to control a number of functions during the playing of a video disc record such as the calculation and display of elapsed playing time, lifting the stylus at the end of the program, and the detection and correction of locked groove conditions.

Abstract: A current source supplies current to an integrator representative of a difference between the instantaneous and average values of a video signal having a PCM data component time division multiplexed with an analog luminance component. The integrator is enabled during the central portion of each PCM signaling interval and reset to a reference level during initial and terminal portions of the intervals. Asymmetry of the peak-to-peak PCM signal levels with respect to the average signal level tends to result in asymmetrical excursions of the integrator output voltage relative to the reference level. This asymmetry is corrected by means of a charge source that supplied a predetermined quantity of charge continuously or in discrete packets to the integrator during the central portion of each PCM signaling interval.